A Medical Device is a Product Which is Used for Medical Purposes in Patients

8/3/2019 A Medical Device is a Product Which is Used for Medical Purposes in Patients

1/20

A medical device is a product which is used for medical purposes in patients, indiagnosis,

therapyorsurgery[citation needed]

. Whereas medicinal products (also calledpharmaceuticals)achieve their principal action by pharmacological, metabolic or immunological means. Medical

devices act by other means like physical, mechanical, thermal, physico-chemical or chemical

means.Medical devices are included in the category:Medical technology.

Medical devices include a wide range of products varying in complexity and application.

Examples includetongue depressors,medical thermometers, [[blood glucose monitoring|bloodsugar meter.

The global market of medical devices reached roughly 209 billion US Dollar in 2006 and isexpected to grow with an average annual rate of 6 - 9% through 2010.[1]

Electrocardiography

From Wikipedia, the free encyclopediaJump to:navigation,search

"ECG" redirects here. For other uses, seeECG (disambiguation).

Not to be confused withechocardiogram,electromyogram,electroencephalogram, orEEG.

Electrocardiography

Intervention
http://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Therapyhttp://en.wikipedia.org/wiki/Therapyhttp://en.wikipedia.org/wiki/Surgeryhttp://en.wikipedia.org/wiki/Surgeryhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Medical_technologyhttp://en.wikipedia.org/wiki/Medical_technologyhttp://en.wikipedia.org/wiki/Medical_technologyhttp://en.wikipedia.org/wiki/Tongue_depressorshttp://en.wikipedia.org/wiki/Tongue_depressorshttp://en.wikipedia.org/wiki/Tongue_depressorshttp://en.wikipedia.org/wiki/Medical_thermometerhttp://en.wikipedia.org/wiki/Medical_thermometerhttp://en.wikipedia.org/wiki/Medical_thermometerhttp://en.wikipedia.org/wiki/Medical_device#cite_note-0http://en.wikipedia.org/wiki/Medical_device#cite_note-0http://en.wikipedia.org/wiki/Medical_device#cite_note-0http://en.wikipedia.org/wiki/Electrocardiography#mw-headhttp://en.wikipedia.org/wiki/Electrocardiography#mw-headhttp://en.wikipedia.org/wiki/Electrocardiography#mw-headhttp://en.wikipedia.org/wiki/Electrocardiography#p-searchhttp://en.wikipedia.org/wiki/Electrocardiography#p-searchhttp://en.wikipedia.org/wiki/Electrocardiography#p-searchhttp://en.wikipedia.org/wiki/ECG_(disambiguation)http://en.wikipedia.org/wiki/ECG_(disambiguation)http://en.wikipedia.org/wiki/ECG_(disambiguation)http://en.wikipedia.org/wiki/Echocardiogramhttp://en.wikipedia.org/wiki/Echocardiogramhttp://en.wikipedia.org/wiki/Echocardiogramhttp://en.wikipedia.org/wiki/Electromyogramhttp://en.wikipedia.org/wiki/Electromyogramhttp://en.wikipedia.org/wiki/Electromyogramhttp://en.wikipedia.org/wiki/Electroencephalogramhttp://en.wikipedia.org/wiki/Electroencephalogramhttp://en.wikipedia.org/wiki/Electroencephalogramhttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/File:ECGcolor.svghttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/Electroencephalogramhttp://en.wikipedia.org/wiki/Electromyogramhttp://en.wikipedia.org/wiki/Echocardiogramhttp://en.wikipedia.org/wiki/ECG_(disambiguation)http://en.wikipedia.org/wiki/Electrocardiography#p-searchhttp://en.wikipedia.org/wiki/Electrocardiography#mw-headhttp://en.wikipedia.org/wiki/Medical_device#cite_note-0http://en.wikipedia.org/wiki/Medical_thermometerhttp://en.wikipedia.org/wiki/Tongue_depressorshttp://en.wikipedia.org/wiki/Medical_technologyhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Surgeryhttp://en.wikipedia.org/wiki/Therapyhttp://en.wikipedia.org/wiki/Diagnosis


2/20

Image showing apatientconnected to the 10 electrodes

necessary for a 12-lead ECG

ICD-9-CM 89.52

MeSH D004562

12 Lead EKG of a 26-year-old male.

Electrocardiography (ECG or EKG from theGermanElektrokardiogramm) is a transthoracic

(across thethoraxor chest) interpretation of theelectricalactivity of theheartover a period of

time, as detected byelectrodesattached to the outer surface of the skin and recorded by a deviceexternal to the body.[1]The recording produced by thisnoninvasiveprocedure is termed an

electrocardiogram (also ECG or EKG).

The etymology of the word is derived from theGreekelectro, because it is related to electrical

activity, kardio,Greekfor heart, and graph, aGreekroot meaning "to write". In English

speaking countries, medical professionals often write EKG (the abbreviation for the Germanword elektrokardiogramm) in order to avoid confusion withEEGin emergency situations wherebackground noise is high.[citation needed]

Most EKGs are performed for diagnostic or research purposes onhuman hearts, but may also beperformed on animals, usually for resea

Function

The EKG device detects and amplifies the tiny electrical changes on the skin that are caused

when theheart muscledepolarizesduring eachheartbeat. At rest, each heart muscle cell has a

charge across its outer wall, orcell membrane. Reducing this charge towards zero is calleddepolarization, which activates the mechanisms in the cell that cause it to contract. During each

heartbeat a healthy heart will have an orderly progression of a wave of depolarisation that is

triggered by the cells in thesinoatrial node, spreads out through the atrium, passes through"intrinsic conduction pathways" and then spreads all over theventricles. This is detected as tiny

rises and falls in thevoltagebetween two electrodes placed either side of the heart which is

displayed as a wavy line either on a screen or on paper. This display indicates the overall rhythmof the heart and weaknesses in different parts of the heart muscle.
http://en.wikipedia.org/wiki/Patienthttp://en.wikipedia.org/wiki/Patienthttp://en.wikipedia.org/wiki/Patienthttp://en.wikipedia.org/wiki/ICD-9-CM_Volume_3http://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?field=uid&term=D004562http://en.wikipedia.org/wiki/German_languagehttp://en.wikipedia.org/wiki/German_languagehttp://en.wikipedia.org/wiki/German_languagehttp://en.wikipedia.org/wiki/Thoraxhttp://en.wikipedia.org/wiki/Thoraxhttp://en.wikipedia.org/wiki/Thoraxhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Hearthttp://en.wikipedia.org/wiki/Hearthttp://en.wikipedia.org/wiki/Hearthttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrocardiography#cite_note-LHC-0http://en.wikipedia.org/wiki/Electrocardiography#cite_note-LHC-0http://en.wikipedia.org/wiki/Electrocardiography#cite_note-LHC-0http://en.wikipedia.org/wiki/Non-invasive_(medical)http://en.wikipedia.org/wiki/Non-invasive_(medical)http://en.wikipedia.org/wiki/Non-invasive_(medical)http://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Human_hearthttp://en.wikipedia.org/wiki/Human_hearthttp://en.wikipedia.org/wiki/Human_hearthttp://en.wikipedia.org/wiki/Cardiac_striated_musclehttp://en.wikipedia.org/wiki/Cardiac_striated_musclehttp://en.wikipedia.org/wiki/Depolarizationhttp://en.wikipedia.org/wiki/Depolarizationhttp://en.wikipedia.org/wiki/Depolarizationhttp://en.wikipedia.org/wiki/Cardiac_cyclehttp://en.wikipedia.org/wiki/Cardiac_cyclehttp://en.wikipedia.org/wiki/Cardiac_cyclehttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Sinoatrial_nodehttp://en.wikipedia.org/wiki/Sinoatrial_nodehttp://en.wikipedia.org/wiki/Sinoatrial_nodehttp://en.wikipedia.org/wiki/Atrium_(heart)http://en.wikipedia.org/wiki/Atrium_(heart)http://en.wikipedia.org/wiki/Ventricle_(heart)http://en.wikipedia.org/wiki/Ventricle_(heart)http://en.wikipedia.org/wiki/Ventricle_(heart)http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/File:12leadECG.jpghttp://en.wikipedia.org/wiki/File:12leadECG.jpghttp://en.wikipedia.org/wiki/File:12leadECG.jpghttp://en.wikipedia.org/wiki/File:12leadECG.jpghttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Ventricle_(heart)http://en.wikipedia.org/wiki/Atrium_(heart)http://en.wikipedia.org/wiki/Sinoatrial_nodehttp://en.wikipedia.org/wiki/Cell_membranehttp://en.wikipedia.org/wiki/Cardiac_cyclehttp://en.wikipedia.org/wiki/Depolarizationhttp://en.wikipedia.org/wiki/Cardiac_striated_musclehttp://en.wikipedia.org/wiki/Human_hearthttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/EEGhttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Non-invasive_(medical)http://en.wikipedia.org/wiki/Electrocardiography#cite_note-LHC-0http://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Hearthttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Thoraxhttp://en.wikipedia.org/wiki/German_languagehttp://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?field=uid&term=D004562http://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://en.wikipedia.org/wiki/ICD-9-CM_Volume_3http://en.wikipedia.org/wiki/Patient


3/20

Usually more than 2 electrodes are used and they can be combined into a number of pairs (For

example: Left arm (LA), right arm (RA) and left leg (LL) electrodes form the three pairsLA+RA, LA+LL, and RA+LL). The output from each pair is known as a lead. Each lead is said

to look at the heart from a different angle. Different types of EKGs can be referred to by the

number ofleadsthat are recorded, for example 3-lead, 5-lead or 12-lead EKGs (sometimes

simply "a 12-lead"). A 12-lead EKG is one in which 12 different electrical signals are recorded atapproximately the same time and will often be used as a one-off recording of an EKG,

traditionally printed out as a paper copy. 3- and 5-lead EKGs tend to be monitored continuously

and viewed only on thescreenof an appropriate monitoring device, for example during anoperation or whilst being transported in an ambulance. There may or may not be any permanent

record of a 3- or 5-lead EKG, depending on the equipment used.

It is the best way to measure and diagnose abnormal rhythms of the heart,[2]

particularly

abnormal rhythms caused by damage to the conductive tissue that carries electrical signals, or

abnormal rhythms caused by electrolyte imbalances.[3]

In amyocardial infarction(MI), the EKGcan identify if the heart muscle has been damaged in specific areas, though not all areas of the

heart are covered.

[4]

The EKG cannot reliably measure the pumping ability of the heart, forwhich ultrasound-based (echocardiography) ornuclear medicinetests are used. It is possible fora human or other animal to be incardiac arrestbut still have a normal EKG signal (a conditionknown aspulseless electrical activity).

X-ray computed tomography

From Wikipedia, the free encyclopedia

Jump to:navigation,search

For non medical computed tomography, seeIndustrial CT Scanning.

"catSCAN" redirects here. For the Transformers character, seeTransformers: Universe.

X-ray computed tomography

Intervention
http://en.wikipedia.org/wiki/Electrocardiography#Leadshttp://en.wikipedia.org/wiki/Electrocardiography#Leadshttp://en.wikipedia.org/wiki/Electrocardiography#Leadshttp://en.wikipedia.org/wiki/Screenhttp://en.wikipedia.org/wiki/Screenhttp://en.wikipedia.org/wiki/Screenhttp://en.wikipedia.org/wiki/Electrocardiography#cite_note-1http://en.wikipedia.org/wiki/Electrocardiography#cite_note-1http://en.wikipedia.org/wiki/Electrocardiography#cite_note-1http://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECG_Noncardiac-2http://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECG_Noncardiac-2http://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECG_Noncardiac-2http://en.wikipedia.org/wiki/Myocardial_infarctionhttp://en.wikipedia.org/wiki/Myocardial_infarctionhttp://en.wikipedia.org/wiki/Myocardial_infarctionhttp://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECC_2005_ACS-3http://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECC_2005_ACS-3http://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECC_2005_ACS-3http://en.wikipedia.org/wiki/Echocardiographyhttp://en.wikipedia.org/wiki/Echocardiographyhttp://en.wikipedia.org/wiki/Echocardiographyhttp://en.wikipedia.org/wiki/Nuclear_medicinehttp://en.wikipedia.org/wiki/Nuclear_medicinehttp://en.wikipedia.org/wiki/Nuclear_medicinehttp://en.wikipedia.org/wiki/Cardiac_arresthttp://en.wikipedia.org/wiki/Cardiac_arresthttp://en.wikipedia.org/wiki/Cardiac_arresthttp://en.wikipedia.org/wiki/Pulseless_electrical_activityhttp://en.wikipedia.org/wiki/Pulseless_electrical_activityhttp://en.wikipedia.org/wiki/Pulseless_electrical_activityhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#mw-headhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#mw-headhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#mw-headhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#p-searchhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#p-searchhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#p-searchhttp://en.wikipedia.org/wiki/Industrial_CT_Scanninghttp://en.wikipedia.org/wiki/Industrial_CT_Scanninghttp://en.wikipedia.org/wiki/Industrial_CT_Scanninghttp://en.wikipedia.org/wiki/Transformers:_Universehttp://en.wikipedia.org/wiki/Transformers:_Universehttp://en.wikipedia.org/wiki/Transformers:_Universehttp://en.wikipedia.org/wiki/Transformers:_Universehttp://en.wikipedia.org/wiki/Industrial_CT_Scanninghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#p-searchhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#mw-headhttp://en.wikipedia.org/wiki/Pulseless_electrical_activityhttp://en.wikipedia.org/wiki/Cardiac_arresthttp://en.wikipedia.org/wiki/Nuclear_medicinehttp://en.wikipedia.org/wiki/Echocardiographyhttp://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECC_2005_ACS-3http://en.wikipedia.org/wiki/Myocardial_infarctionhttp://en.wikipedia.org/wiki/Electrocardiography#cite_note-ECG_Noncardiac-2http://en.wikipedia.org/wiki/Electrocardiography#cite_note-1http://en.wikipedia.org/wiki/Screenhttp://en.wikipedia.org/wiki/Electrocardiography#Leads


4/20

A patient is receiving a CT scan forcancer. Outside of the

scanning room is an imaging computer that reveals a3D

imageof the body's interior.

ICD-10-PCS B?2

ICD-9-CM 88.38

MeSH D014057

OPS-301 code: 3-20...3-26

X-ray computed tomography (CT) is amedical imagingmethod employingtomographycreated by computer processing.

[1]Digital geometry processingis used to generate athree-

dimensionalimage of the inside of an object from a large series of two-dimensionalX-rayimages taken around a singleaxis of rotation.

[2]

CT produces a volume of data that can be manipulated, through a process known as

"windowing", in order to demonstrate various bodily structures based on their ability to block the

X-ray beam. Although historically the images generated were in the axial or transverse plane,orthogonalto the long axis of the body, modern scanners allow this volume of data to be

reformatted in various planes or even as volumetric (3D) representations of structures. Although

most common in medicine, CT is also used in other fields, such asnondestructive materialstesting. Another example is archaeological uses such as imaging the contents of sarcophagi.

Usage of CT has increased dramatically over the last two decades in many countries .[3]

Anestimated 72 million scans were performed in the United States in 2007.[4]It is estimated that

0.4% of current cancers in the United States are due to CTs performed in the past and that this

may increase to as high as 1.5-2% with 2007 rates of CT usage;[5]

however, this estimate isdisputed.[6]
http://en.wikipedia.org/wiki/Cancerhttp://en.wikipedia.org/wiki/Cancerhttp://en.wikipedia.org/wiki/Cancerhttp://en.wikipedia.org/wiki/3D_imagehttp://en.wikipedia.org/wiki/3D_imagehttp://en.wikipedia.org/wiki/3D_imagehttp://en.wikipedia.org/wiki/3D_imagehttp://en.wikipedia.org/wiki/ICD-10_Procedure_Coding_Systemhttp://en.wikipedia.org/wiki/ICD-9-CM_Volume_3http://icd9cm.chrisendres.com/index.php?srchtype=procs&srchtext=88.38&Submit=Search&action=searchhttp://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?field=uid&term=D014057http://en.wikipedia.org/wiki/OPS-301http://ops.icd-code.de/ops/code/3-20...3-26.htmlhttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Tomographyhttp://en.wikipedia.org/wiki/Tomographyhttp://en.wikipedia.org/wiki/Tomographyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-urlcomputed_tomography.E2.80.94Definition_from_the_Merriam-Webster_Online_Dictionary-0http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-urlcomputed_tomography.E2.80.94Definition_from_the_Merriam-Webster_Online_Dictionary-0http://en.wikipedia.org/wiki/Geometry_Processinghttp://en.wikipedia.org/wiki/Geometry_Processinghttp://en.wikipedia.org/wiki/Geometry_Processinghttp://en.wikipedia.org/wiki/Three-dimensional_spacehttp://en.wikipedia.org/wiki/Three-dimensional_spacehttp://en.wikipedia.org/wiki/Three-dimensional_spacehttp://en.wikipedia.org/wiki/Three-dimensional_spacehttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Axis_of_rotationhttp://en.wikipedia.org/wiki/Axis_of_rotationhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/Computed_tomography#Windowinghttp://en.wikipedia.org/wiki/Computed_tomography#Windowinghttp://en.wiktionary.org/wiki/orthogonalhttp://en.wiktionary.org/wiki/orthogonalhttp://en.wikipedia.org/wiki/Nondestructive_testinghttp://en.wikipedia.org/wiki/Nondestructive_testinghttp://en.wikipedia.org/wiki/Nondestructive_testinghttp://en.wikipedia.org/wiki/Nondestructive_testinghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-4http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-4http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-4http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-5http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-5http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-5http://en.wikipedia.org/wiki/File:Rosies_ct_scan.jpghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-5http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-4http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/wiki/Nondestructive_testinghttp://en.wikipedia.org/wiki/Nondestructive_testinghttp://en.wiktionary.org/wiki/orthogonalhttp://en.wikipedia.org/wiki/Computed_tomography#Windowinghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/Axis_of_rotationhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Three-dimensional_spacehttp://en.wikipedia.org/wiki/Three-dimensional_spacehttp://en.wikipedia.org/wiki/Geometry_Processinghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-urlcomputed_tomography.E2.80.94Definition_from_the_Merriam-Webster_Online_Dictionary-0http://en.wikipedia.org/wiki/Tomographyhttp://en.wikipedia.org/wiki/Medical_imaginghttp://ops.icd-code.de/ops/code/3-20...3-26.htmlhttp://en.wikipedia.org/wiki/OPS-301http://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?field=uid&term=D014057http://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://icd9cm.chrisendres.com/index.php?srchtype=procs&srchtext=88.38&Submit=Search&action=searchhttp://en.wikipedia.org/wiki/ICD-9-CM_Volume_3http://en.wikipedia.org/wiki/ICD-10_Procedure_Coding_Systemhttp://en.wikipedia.org/wiki/3D_imagehttp://en.wikipedia.org/wiki/3D_imagehttp://en.wikipedia.org/wiki/Cancer


5/20

Contents

1 Terminology 2 Diagnostic use

o 2.1 Heado 2.2 Lungso 2.3 Pulmonary angiogramo 2.4 Cardiaco 2.5 Abdominal and pelvico 2.6 Extremities

3 Advantages 4 Adverse effects

o 4.1 Typical scan doseo 4.2 Reactions to contrast agentso 4.3 Low-dose CT scan

5 Artifacts 6 Prevalence 7 Process 8 Three-dimensional reconstruction

o 8.1 Multiplanar reconstructiono 8.2 3D rendering techniqueso 8.3 Volume renderingo 8.4 Image segmentation

9 Industrial use 10 History

o 10.1 Previous studies 10.1.1 Tomosynthesis

11 See also 12 References 13 External links

[edit] Terminology

The word "tomography" is derived from theGreektomos (slice) and graphein (to write).Computed tomography was originally known as the "EMI scan" as it was developed at a research

branch ofEMI, a company best known today for its music and recording business. It was laterknown as computed axial tomography (CAT or CT scan) and body section rntgenography.

Although the term "computed tomography" could be used to describepositron emission

tomographyandsingle photon emission computed tomography, in practice it usually refers to the

computation of tomography fromX-rayimages, especially in older medical literature and

smaller medical facilities.

InMeSH, "computed axial tomography" was used from 197779, but the current indexingexplicitly includes "X-ray" in the title.[7]
http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-5http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-5http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-5http://en.wikipedia.org/wiki/X-ray_computed_tomography#Terminologyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Terminologyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Diagnostic_usehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Diagnostic_usehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Headhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Headhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Lungshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Lungshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Pulmonary_angiogramhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Pulmonary_angiogramhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Cardiachttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Cardiachttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Abdominal_and_pelvichttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Abdominal_and_pelvichttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Extremitieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Extremitieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Advantageshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Advantageshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Adverse_effectshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Adverse_effectshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Typical_scan_dosehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Typical_scan_dosehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Reactions_to_contrast_agentshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Reactions_to_contrast_agentshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Low-dose_CT_scanhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Low-dose_CT_scanhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Artifactshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Artifactshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Prevalencehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Prevalencehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Processhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Processhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Three-dimensional_reconstructionhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Three-dimensional_reconstructionhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Multiplanar_reconstructionhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Multiplanar_reconstructionhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#3D_rendering_techniqueshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#3D_rendering_techniqueshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Volume_renderinghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Volume_renderinghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Image_segmentationhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Image_segmentationhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Industrial_usehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Industrial_usehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Historyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Historyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Previous_studieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Previous_studieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Tomosynthesishttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Tomosynthesishttp://en.wikipedia.org/wiki/X-ray_computed_tomography#See_alsohttp://en.wikipedia.org/wiki/X-ray_computed_tomography#See_alsohttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Referenceshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Referenceshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#External_linkshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#External_linkshttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=1http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=1http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=1http://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/EMIhttp://en.wikipedia.org/wiki/EMIhttp://en.wikipedia.org/wiki/EMIhttp://en.wikipedia.org/wiki/Positron_emission_tomographyhttp://en.wikipedia.org/wiki/Positron_emission_tomographyhttp://en.wikipedia.org/wiki/Positron_emission_tomographyhttp://en.wikipedia.org/wiki/Positron_emission_tomographyhttp://en.wikipedia.org/wiki/Single_photon_emission_computed_tomographyhttp://en.wikipedia.org/wiki/Single_photon_emission_computed_tomographyhttp://en.wikipedia.org/wiki/Single_photon_emission_computed_tomographyhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-6http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-6http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-6http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-6http://en.wikipedia.org/wiki/Medical_Subject_Headingshttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Single_photon_emission_computed_tomographyhttp://en.wikipedia.org/wiki/Positron_emission_tomographyhttp://en.wikipedia.org/wiki/Positron_emission_tomographyhttp://en.wikipedia.org/wiki/EMIhttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=1http://en.wikipedia.org/wiki/X-ray_computed_tomography#External_linkshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Referenceshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#See_alsohttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Tomosynthesishttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Previous_studieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Historyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Industrial_usehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Image_segmentationhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Volume_renderinghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#3D_rendering_techniqueshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Multiplanar_reconstructionhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Three-dimensional_reconstructionhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Processhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Prevalencehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Artifactshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Low-dose_CT_scanhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Reactions_to_contrast_agentshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Typical_scan_dosehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Adverse_effectshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Advantageshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Extremitieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Abdominal_and_pelvichttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Cardiachttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Pulmonary_angiogramhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Lungshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Headhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Diagnostic_usehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#Terminology


6/20

[edit] Diagnostic use

Since its introduction in the 1970s, CT has become an important tool inmedical imagingtosupplementX-raysandmedical ultrasonography. It has more recently been used forpreventive

medicineorscreeningfor disease, for example CT colonography for patients with a high risk of

colon cancer, or full-motion heart scans for patients with high risk of heart disease. A number ofinstitutions offerfull-body scansfor the general population.

[edit] Head

Main article:CT head

Computed tomography ofhuman brain, frombase of the skullto top. Taken with intravenous contrast

medium.

Bone reconstructed in 3D

CT scanning of the head is typically used to detectinfarction, tumours,calcifications,haemorrhage and bone trauma. Of the above, hypodense (dark) structures indicate infarction or

tumours, hyperdense (bright) structures indicate calcifications andhaemorrhageand bone trauma
http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=2http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=2http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=2http://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Medical_ultrasonographyhttp://en.wikipedia.org/wiki/Medical_ultrasonographyhttp://en.wikipedia.org/wiki/Medical_ultrasonographyhttp://en.wikipedia.org/wiki/Preventive_medicinehttp://en.wikipedia.org/wiki/Preventive_medicinehttp://en.wikipedia.org/wiki/Preventive_medicinehttp://en.wikipedia.org/wiki/Preventive_medicinehttp://en.wikipedia.org/wiki/Screening_(medicine)http://en.wikipedia.org/wiki/Screening_(medicine)http://en.wikipedia.org/wiki/Screening_(medicine)http://en.wikipedia.org/wiki/Full-body_scanhttp://en.wikipedia.org/wiki/Full-body_scanhttp://en.wikipedia.org/wiki/Full-body_scanhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=3http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=3http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=3http://en.wikipedia.org/wiki/CT_headhttp://en.wikipedia.org/wiki/CT_headhttp://en.wikipedia.org/wiki/CT_headhttp://en.wikipedia.org/wiki/Human_brainhttp://en.wikipedia.org/wiki/Human_brainhttp://en.wikipedia.org/wiki/Human_brainhttp://en.wikipedia.org/wiki/Base_of_the_skullhttp://en.wikipedia.org/wiki/Base_of_the_skullhttp://en.wikipedia.org/wiki/Base_of_the_skullhttp://en.wikipedia.org/wiki/Infarctionhttp://en.wikipedia.org/wiki/Infarctionhttp://en.wikipedia.org/wiki/Infarctionhttp://en.wikipedia.org/wiki/Calcificationhttp://en.wikipedia.org/wiki/Calcificationhttp://en.wikipedia.org/wiki/Calcificationhttp://en.wikipedia.org/wiki/Tumourhttp://en.wikipedia.org/wiki/Tumourhttp://en.wikipedia.org/wiki/Haemorrhagehttp://en.wikipedia.org/wiki/Haemorrhagehttp://en.wikipedia.org/wiki/Haemorrhagehttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Bonereconstruction.jpghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/File:Computed_tomography_of_human_brain_-_large.pnghttp://en.wikipedia.org/wiki/Haemorrhagehttp://en.wikipedia.org/wiki/Tumourhttp://en.wikipedia.org/wiki/Calcificationhttp://en.wikipedia.org/wiki/Infarctionhttp://en.wikipedia.org/wiki/Base_of_the_skullhttp://en.wikipedia.org/wiki/Human_brainhttp://en.wikipedia.org/wiki/CT_headhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=3http://en.wikipedia.org/wiki/Full-body_scanhttp://en.wikipedia.org/wiki/Screening_(medicine)http://en.wikipedia.org/wiki/Preventive_medicinehttp://en.wikipedia.org/wiki/Preventive_medicinehttp://en.wikipedia.org/wiki/Medical_ultrasonographyhttp://en.wikipedia.org/wiki/X-rayhttp://en.wikipedia.org/wiki/Medical_imaginghttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=2


7/20

can be seen as disjunction in bone windows. Ambulances equipped with small bore multi-sliced

CT scanners respond to cases involving stroke or head trauma.

[edit] Lungs

CT can be used for detecting both acute and chronic changes in thelungparenchyma, that is, theinternals of the lungs. It is particularly relevant here because normal two-dimensional X-rays donot show such defects. A variety of different techniques are used, depending on the suspected

abnormality. For evaluation of chronic interstitial processes (emphysema,fibrosis, and so forth),

thin sections with high spatial frequency reconstructions are used; often scans are performed

both in inspiration and expiration. This special technique is called high resolution CT. Therefore,it produces a sampling of the lung and not continuous images.

[edit] Pulmonary angiogram

Example of a CTPA, demonstrating a saddleembolus(dark horizontal line) occluding thepulmonary

arteries(bright white triangle)

CT pulmonary angiogram(CTPA) is a medical diagnostic test used to diagnosepulmonaryembolism(PE). It employs computed tomography to obtain an image of thepulmonary arteries.

[edit] Cardiac

Main article:Cardiac CT

With the advent of subsecond rotation combined with multi-slice CT (up to 320-slices), high

resolution and high speed can be obtained at the same time, allowing excellent imaging of the

coronary arteries (cardiac CT angiography).

[edit] Abdominal and pelvic

Main article:Abdominal and pelvic CT
http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=4http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=4http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=4http://en.wikipedia.org/wiki/Human_lunghttp://en.wikipedia.org/wiki/Human_lunghttp://en.wikipedia.org/wiki/Human_lunghttp://en.wikipedia.org/wiki/Emphysemahttp://en.wikipedia.org/wiki/Emphysemahttp://en.wikipedia.org/wiki/Emphysemahttp://en.wikipedia.org/wiki/Fibrosishttp://en.wikipedia.org/wiki/Fibrosishttp://en.wikipedia.org/wiki/Fibrosishttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=5http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=5http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=5http://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/CT_pulmonary_angiogramhttp://en.wikipedia.org/wiki/CT_pulmonary_angiogramhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=6http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=6http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=6http://en.wikipedia.org/wiki/Cardiac_CThttp://en.wikipedia.org/wiki/Cardiac_CThttp://en.wikipedia.org/wiki/Cardiac_CThttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=7http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=7http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=7http://en.wikipedia.org/wiki/Abdominal_and_pelvic_CThttp://en.wikipedia.org/wiki/Abdominal_and_pelvic_CThttp://en.wikipedia.org/wiki/Abdominal_and_pelvic_CThttp://en.wikipedia.org/wiki/File:SADDLE_PE.JPGhttp://en.wikipedia.org/wiki/File:SADDLE_PE.JPGhttp://en.wikipedia.org/wiki/File:SADDLE_PE.JPGhttp://en.wikipedia.org/wiki/File:SADDLE_PE.JPGhttp://en.wikipedia.org/wiki/Abdominal_and_pelvic_CThttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=7http://en.wikipedia.org/wiki/Cardiac_CThttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=6http://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/wiki/CT_pulmonary_angiogramhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_arteryhttp://en.wikipedia.org/wiki/Pulmonary_embolismhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=5http://en.wikipedia.org/wiki/Fibrosishttp://en.wikipedia.org/wiki/Emphysemahttp://en.wikipedia.org/wiki/Human_lunghttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=4


8/20

CT Scanof 11 cmWilms' tumorof right kidney in 13 month old patient.

CT is a sensitive method for diagnosis ofabdominaldiseases. It is used frequently to determinestage of cancer and to follow progress. It is also a useful test to investigate acute abdominal pain.

[edit] Extremities

CT is often used to image complexfractures, especially ones around joints, because of its abilityto reconstruct the area of interest in multiple planes. Fractures, ligamentous injuries and

dislocations can easily be recognised with a 0.2 mm resolution.[8][9]

[edit] Advantages

There are several advantages that CT has over traditional 2Dmedical radiography. First, CT

completely eliminates the superimposition of images of structures outside the area of interest.Second, because of the inherent high-contrast resolution of CT, differences between tissues that

differ in physical density by less than 1% can be distinguished. Finally, data from a single CT

imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as

images in the axial, coronal, or sagittal planes, depending on the diagnostic task. This is referredto as multiplanar reformatted imaging.

CT is regarded as a moderate- to high-radiationdiagnostic technique. The improved resolution ofCT has permitted the development of new investigations, which may have advantages; compared

to conventional radiography, for example, CT angiography avoids the invasive insertion of acatheter. CT Colonography (also known as Virtual Colonoscopy or VC for short) may be as

useful as a barium enema for detection of tumors, but may use a lower radiation dose. CT VC isincreasingly being used in the UK as a diagnostic test for bowel cancer and can negate the need

for a colonoscopy.

The radiation dose for a particular study depends on multiple factors: volume scanned, patient

build, number and type of scan sequences, and desired resolution and image quality. In addition,
http://en.wikipedia.org/wiki/Abdominal_and_pelvic_CThttp://en.wikipedia.org/wiki/Computed_tomographyhttp://en.wikipedia.org/wiki/Computed_tomographyhttp://en.wikipedia.org/wiki/Wilms%27_tumorhttp://en.wikipedia.org/wiki/Wilms%27_tumorhttp://en.wikipedia.org/wiki/Wilms%27_tumorhttp://en.wikipedia.org/wiki/Human_abdomenhttp://en.wikipedia.org/wiki/Human_abdomenhttp://en.wikipedia.org/wiki/Human_abdomenhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=8http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=8http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=8http://en.wikipedia.org/wiki/Fracture_(bone)http://en.wikipedia.org/wiki/Fracture_(bone)http://en.wikipedia.org/wiki/Fracture_(bone)http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-7http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-7http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-7http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=9http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=9http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=9http://en.wikipedia.org/wiki/Medical_radiographyhttp://en.wikipedia.org/wiki/Medical_radiographyhttp://en.wikipedia.org/wiki/Medical_radiographyhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/File:Wilms_Tumor_CTScan.OGGhttp://en.wikipedia.org/wiki/File:Wilms_Tumor_CTScan.OGGhttp://en.wikipedia.org/wiki/File:Wilms_Tumor_CTScan.OGGhttp://en.wikipedia.org/wiki/File:Wilms_Tumor_CTScan.OGGhttp://en.wikipedia.org/wiki/File:Wilms_Tumor_CTScan.OGGhttp://en.wikipedia.org/wiki/File:Wilms_Tumor_CTScan.OGGhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Medical_radiographyhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=9http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-7http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-7http://en.wikipedia.org/wiki/Fracture_(bone)http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=8http://en.wikipedia.org/wiki/Human_abdomenhttp://en.wikipedia.org/wiki/Wilms%27_tumorhttp://en.wikipedia.org/wiki/Computed_tomography


9/20

two helical CT scanning parameters that can be adjusted easily and that have a profound effect

on radiation dose are tube current and pitch. Computed tomography (CT) scan has been shown tobe more accurate than radiographs in evaluating anterior interbody fusion but may still over-read

the extent of fusion.[10]

[edit] Adverse effects

The increased use of CT scans has been the greatest in two fields: screening of adults (screeningCT of the lung in smokers, virtual colonoscopy, CT cardiac screening, and whole-body CT inasymptomatic patients) and CT imaging of children. Shortening of the scanning time to around 1

second, eliminating the strict need for the subject to remain still or be sedated, is one of the main

reasons for the large increase in the pediatric population (especially for the diagnosis of

appendicitis).[11]

CT scans of children have been estimated to produce non-negligible increases inthe probability of lifetime cancer mortality, leading to calls for the use of reduced current settings

for CT scans of children.[12]

These calculations are based on similar radiation exposures experienced by those present duringtheatomic bombexplosions in Japan during the second world war andnuclear industryworks.

[11]

Estimated lifetime cancer mortality risks attributable to the radiation exposure from a CT in a 1-year-old are 0.18% (abdominal) and 0.07% (head) an order of magnitude higher than for

adults although those figures still represent a small increase in cancer mortality over the

background rate. In the United States, of approximately 600,000 abdominal and head CTexaminations annually performed in children under the age of 15 years, a rough estimate is that

500 of these individuals might ultimately die from cancer attributable to the CT radiation.[13]

The

additional risk is still low: 0.35% compared to the background risk of dying from cancer of

23%.[13]

However, if these statistics are extrapolated to the current number of CT scans, theadditional rise in cancer mortality could be 1.5 to 2%. Furthermore, certain conditions can

require children to be exposed to multiple CT scans.[11]

In 2009, a number of studies that further defined the risk of cancer that may be caused by CT

scans appeared.[14]

One study indicated that radiation by CT scans is often higher and more

variable than cited, and each of the 19,500 CT scans that are daily performed in the US isequivalent to 30 to 442 chest X-rays in radiation. It has been estimated that CT radiation

exposure will result in 29,000 new cancer cases just from the CT scans performed in 2007.[14]

The most common cancers caused by CT are thought to belung cancer,colon cancer, andleukemiawith younger people, and women more at risk. These conclusions, however, are

criticized by theAmerican College of Radiology(ACR), which maintains that the life

expectancy of CT scanned patients is not that of the general population and that the model of

calculating cancer is based on total-body radiation exposure and thus faulty.[14]

CT scans can be performed with different settings for lower exposure in children, although these

techniques are often not employed. Surveys have suggested that, at the current time, many CTscans are performed unnecessarily.Ultrasound scanningormagnetic resonance imagingare

alternatives (for example, in appendicitis or brain imaging) without the risk of radiation

exposure. Although CT scans come with an additional risk of cancer (it can be estimated that theradiation exposure from a full body scan is the same as standing 2.4 km away from theWorld
http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-9http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-9http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-9http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=10http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=10http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=10http://en.wikipedia.org/wiki/Appendicitishttp://en.wikipedia.org/wiki/Appendicitishttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-11http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-11http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-11http://en.wikipedia.org/wiki/Atomic_bombhttp://en.wikipedia.org/wiki/Atomic_bombhttp://en.wikipedia.org/wiki/Atomic_bombhttp://en.wikipedia.org/wiki/Nuclear_industryhttp://en.wikipedia.org/wiki/Nuclear_industryhttp://en.wikipedia.org/wiki/Nuclear_industryhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/Lung_cancerhttp://en.wikipedia.org/wiki/Lung_cancerhttp://en.wikipedia.org/wiki/Lung_cancerhttp://en.wikipedia.org/wiki/Colon_cancerhttp://en.wikipedia.org/wiki/Colon_cancerhttp://en.wikipedia.org/wiki/Colon_cancerhttp://en.wikipedia.org/wiki/Leukemiahttp://en.wikipedia.org/wiki/Leukemiahttp://en.wikipedia.org/wiki/American_College_of_Radiologyhttp://en.wikipedia.org/wiki/American_College_of_Radiologyhttp://en.wikipedia.org/wiki/American_College_of_Radiologyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/Ultrasound_scanninghttp://en.wikipedia.org/wiki/Ultrasound_scanninghttp://en.wikipedia.org/wiki/Ultrasound_scanninghttp://en.wikipedia.org/wiki/Magnetic_resonance_imaginghttp://en.wikipedia.org/wiki/Magnetic_resonance_imaginghttp://en.wikipedia.org/wiki/Magnetic_resonance_imaginghttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/Magnetic_resonance_imaginghttp://en.wikipedia.org/wiki/Ultrasound_scanninghttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/American_College_of_Radiologyhttp://en.wikipedia.org/wiki/Leukemiahttp://en.wikipedia.org/wiki/Colon_cancerhttp://en.wikipedia.org/wiki/Lung_cancerhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-medscape-13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/Nuclear_industryhttp://en.wikipedia.org/wiki/Atomic_bombhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-11http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/Appendicitishttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-9


10/20

War IIatomic bomb blasts in Japan[15][16]

), especially in children, the benefits that stem from

their use outweigh the risk in many cases.[13]

Studies support informing parents of the risks ofpediatric CT scanning.[17]

[edit] Typical scan dose

Examination Typicaleffective dose(mSv)(millirem)

X-ray Personnel security screening scan0.00025 0.025[18]

Chest X-ray 0.1 10

Head CT 1.5[19] 150

Screeningmammography 3[11] 300

Abdomen CT 5.3[19] 530

Chest CT 5.8[19] 580

CT colonography (virtual colonoscopy) 3.68.8 360880

Chest, abdomen and pelvis CT 9.9[19] 990

Cardiac CT angiogram 6.7-13[20] 6701300

Barium enema 15[11] 1500

Neonatal abdominal CT 20[11] 2000

For purposes of comparison, the averagebackground exposurein the UK is 1-3 mSv per year.

[edit] Reactions to contrast agents

This section does notciteanyreferences or sources. Please help improve this section by

adding citations toreliable sources. Unsourced material may bechallengedandremoved.

(September 2009)

Because contrast CT scans rely onintravenously administeredcontrast agentsin order to providesuperior image quality, there is a low but non-negligible level of risk associated with the contrast

agents themselves. Many patients report nausea and discomfort, including warmth in the crotch,

which mimics the sensation of wetting oneself. Certain patients may experiencesevere andpotentially life-threatening allergic reactionsto the contrast dye.
http://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-14http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-14http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid17646450-16http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid17646450-16http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid17646450-16http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=11http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=11http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=11http://en.wikipedia.org/wiki/Effective_dosehttp://en.wikipedia.org/wiki/Effective_dosehttp://en.wikipedia.org/wiki/Effective_dosehttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-17http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-17http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/Mammographyhttp://en.wikipedia.org/wiki/Mammographyhttp://en.wikipedia.org/wiki/Mammographyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/Virtual_colonoscopyhttp://en.wikipedia.org/wiki/Virtual_colonoscopyhttp://en.wikipedia.org/wiki/Virtual_colonoscopyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-19http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-19http://en.wikipedia.org/wiki/Barium_enemahttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/Background_radiationhttp://en.wikipedia.org/wiki/Background_radiationhttp://en.wikipedia.org/wiki/Background_radiationhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=12http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=12http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=12http://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/Intravenous_therapyhttp://en.wikipedia.org/wiki/Intravenous_therapyhttp://en.wikipedia.org/wiki/Radiocontrasthttp://en.wikipedia.org/wiki/Radiocontrasthttp://en.wikipedia.org/wiki/Radiocontrasthttp://en.wikipedia.org/wiki/Anaphylaxishttp://en.wikipedia.org/wiki/Anaphylaxishttp://en.wikipedia.org/wiki/Anaphylaxishttp://en.wikipedia.org/wiki/Anaphylaxishttp://en.wikipedia.org/wiki/Anaphylaxishttp://en.wikipedia.org/wiki/Anaphylaxishttp://en.wikipedia.org/wiki/Radiocontrasthttp://en.wikipedia.org/wiki/Intravenous_therapyhttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=12http://en.wikipedia.org/wiki/Background_radiationhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/Barium_enemahttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-19http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/Virtual_colonoscopyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-NEJM-radiation-10http://en.wikipedia.org/wiki/Mammographyhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-nrpb2005-18http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-17http://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Effective_dosehttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=11http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid17646450-16http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-pmid11159059-12http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-14http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-14http://en.wikipedia.org/wiki/World_War_II


11/20

The contrast agent may also inducekidney damage. The risk of this is increased with patients

who have preexistingrenal insufficiency, preexistingdiabetes, or reduced intravascular volume.In general, if a patient has normal kidney function, then the risks of contrast nephropathy are

negligible. Patients with mild kidney impairment are usually advised to ensure full hydration for

several hours before and after the injection. For moderate kidney failure, the use ofiodinated

contrastshould be avoided; this may mean using an alternative technique instead of CT, e.g.,MRI. However, patients with severe renal failure requiring dialysis do not require special

precautions, as their kidneys have so little function remaining that any further damage would not

be noticeable and the dialysis will remove the contrast agent.

[edit] Low-dose CT scan

An important issue within radiology today is how to reduce the radiation dose during CT

examinations without compromising the image quality. In general, higher radiation doses result

in higher-resolution images, while lower doses lead to increased image noise and unsharpimages. Increased dosage raises the risk of radiation induced cancera four-phase abdominal

CT gives the same radiation dose as 300 chest x-rays. Several methods that can reduce theexposure to ionizing radiation during a CT scan exist.

1. New software technology can significantly reduce the required radiation dose.2. Individualize the examination and adjust the radiation dose to the body type and body organ

examined. Different body types and organs require different amounts of radiation.

3. Prior to every CT examination, evaluate the appropriateness of the exam whether it is motivatedor if another type of examination is more suitable. Higher resolution is not always suitable for

any given scenario, such as detection of small pulmonary masses[21]

[edit] Artifacts

This section does notciteanyreferences or sources. Please help improve this section by

adding citations toreliable sources. Unsourced material may bechallengedandremoved.

(September 2009)

Although CT is a relatively accurate test, it is liable to produce artifacts, such as the following:[2],

Chapters 3 and 5

Streak artifactStreaks are often seen around materials that block most X-rays, such as metal or bone. Thesestreaks can be caused by undersampling, photon starvation, motion, beam hardening, or scatter.

This type of artifact commonly occurs in the posterior fossa of the brain, or if there are metal

implants. The streaks can be reduced using newer reconstruction techniques.[22]

Partial volume effect
http://en.wikipedia.org/wiki/Nephropathyhttp://en.wikipedia.org/wiki/Nephropathyhttp://en.wikipedia.org/wiki/Nephropathyhttp://en.wikipedia.org/wiki/Renal_failurehttp://en.wikipedia.org/wiki/Renal_failurehttp://en.wikipedia.org/wiki/Renal_failurehttp://en.wikipedia.org/wiki/Diabetes_mellitushttp://en.wikipedia.org/wiki/Diabetes_mellitushttp://en.wikipedia.org/wiki/Diabetes_mellitushttp://en.wikipedia.org/wiki/Iodinated_contrasthttp://en.wikipedia.org/wiki/Iodinated_contrasthttp://en.wikipedia.org/wiki/Iodinated_contrasthttp://en.wikipedia.org/wiki/Iodinated_contrasthttp://en.wikipedia.org/wiki/MRIhttp://en.wikipedia.org/wiki/MRIhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=13http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=13http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=13http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-20http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-20http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-20http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=14http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=14http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=14http://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-21http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-21http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-21http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-21http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-ref1-1http://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidencehttp://en.wikipedia.org/wiki/Template:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Verifiabilityhttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=14http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-20http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=13http://en.wikipedia.org/wiki/MRIhttp://en.wikipedia.org/wiki/Iodinated_contrasthttp://en.wikipedia.org/wiki/Iodinated_contrasthttp://en.wikipedia.org/wiki/Diabetes_mellitushttp://en.wikipedia.org/wiki/Renal_failurehttp://en.wikipedia.org/wiki/Nephropathy


12/20

This appears as "blurring" over sharp edges. It is due to the scanner being unable to differentiate

between a small amount of high-density material (e.g., bone) and a larger amount of lowerdensity (e.g., cartilage). The processor tries to average out the two densities or structures, and

information is lost. This can be partially overcome by scanning using thinner slices.

Ring artifact

Probably the most common mechanical artifact, the image of one or many "rings" appears within

an image. This is usually due to a detector fault.

Noise artifactThis appears as graining on the image and is caused by a low signal to noise ratio. This occurs

more commonly when a thin slice thickness is used. It can also occur when the power supplied to

the X-ray tube is insufficient to penetrate the anatomy.

Motion artifactThis is seen as blurring and/or streaking, which is caused by movement of the object beingimaged. Motion blurring might be reduced using a new technique called IFT (incompressible

flow tomography).[23]

WindmillStreaking appearances can occur when the detectors intersect the reconstruction plane. This can

be reduced with filters or a reduction in pitch.

Beam hardeningThis can give a "cupped appearance". It occurs when there is moreattenuationin the center of

the object than around the edge. This is easily corrected by filtration and software.

[edit] Prevalence

Usage of CT has increased dramatically over the last two decades.[3]

An estimated 72 millionscans were performed in the United States in 2007.

[4]In Calgary, Canada 12.1% of people who

present to the emergency with an urgent complaint received a CT scan, most commonly either of

the head or of the abdomen. The percentage who received CT, however, varied markedly by the

emergency physicianwho saw them from 1.8% to 25%.[24]

In the emergency department in theUnited States, CT or MRI imaging is done in 15% of people who present withinjuriesas of 2007(up from 6% in 1998).[25]
http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-22http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-22http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-22http://en.wikipedia.org/wiki/Attenuation_(electromagnetic_radiation)http://en.wikipedia.org/wiki/Attenuation_(electromagnetic_radiation)http://en.wikipedia.org/wiki/Attenuation_(electromagnetic_radiation)http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=15http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=15http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=15http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/Emergency_physicianhttp://en.wikipedia.org/wiki/Emergency_physicianhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-23http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-23http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-23http://en.wikipedia.org/wiki/Injurieshttp://en.wikipedia.org/wiki/Injurieshttp://en.wikipedia.org/wiki/Injurieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-24http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-24http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-24http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-24http://en.wikipedia.org/wiki/Injurieshttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-23http://en.wikipedia.org/wiki/Emergency_physicianhttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Berrington_de_Gonz.C3.A1lez_A.2C_Mahesh_M.2C_Kim_KP.2C_et_al._2009_2071.E2.80.937-3http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-Smith-Bindman_R.2C_Lipson_J.2C_Marcus_R.2C_et_al._2009_2078.E2.80.9386-2http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=15http://en.wikipedia.org/wiki/Attenuation_(electromagnetic_radiation)http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-22


13/20

[edit] Process

3D reconstruction of the brain and eyeballs from CT scanned DICOM images. In this image, areas with

the density of bone or air were made transparent, and the slices stacked up in an approximate free-

space alignment. The outer ring of material around the brain are the soft tissues of skin and muscle on

the outside of the skull. A black box encloses the slices to provide the black background. Since these are

simply 2D images stacked up, when viewed on edge the slices disappear since they have effectively zero

thickness. Each DICOM scan represents about 5mm of material averaged into a thin slice.

X-ray slice data is generated using an X-ray source that rotates around the object; X-ray sensorsare positioned on the opposite side of the circle from the X-ray source. The earliest sensors were

scintillation detectors, withphotomultiplier tubesexcited by (typically)cesium iodidecrystals.

Cesium iodide was replaced during the 1980s byion chamberscontaining high-pressureXenon

gas. These systems were in turn replaced by scintillation systems based onphotodiodesinstead

of photomultipliers and modern scintillation materials with more desirable characteristics. Manydata scans are progressively taken as the object is gradually passed through the gantry.

Newer machines with faster computer systems and newer software strategies can process not

only individual cross sections but continuously changing cross sections as the gantry, with the

object to be imaged slowly and smoothly slid through the X-ray circle. These are called helicalorspiral CTmachines. Their computer systems integrate the data of the moving individual slices

to generate three dimensional volumetric information (3D-CT scan), in turn viewable from

multiple different perspectives on attached CT workstation monitors. This type of dataacquisition requires enormous processing power, as the data are arriving in a continuous streamand must be processed in real-time.

In conventional CT machines, anX-ray tubeand detector are physically rotated behind a circularshroud (see the image above right); in theelectron beam tomography(EBT), the tube is far larger

and higher power to support the high temporal resolution. The electron beam is deflected in a

hollow funnel-shaped vacuum chamber. X-rays are generated when the beam hits the stationarytarget. The detector is also stationary. This arrangement can result in very fast scans, but is

extremely expensive.
http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=16http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=16http://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=16http://en.wikipedia.org/wiki/Scintillation_detectorhttp://en.wikipedia.org/wiki/Scintillation_detectorhttp://en.wikipedia.org/wiki/Photomultiplier_tubehttp://en.wikipedia.org/wiki/Photomultiplier_tubehttp://en.wikipedia.org/wiki/Photomultiplier_tubehttp://en.wikipedia.org/wiki/Cesium_iodidehttp://en.wikipedia.org/wiki/Cesium_iodidehttp://en.wikipedia.org/wiki/Cesium_iodidehttp://en.wikipedia.org/wiki/Ion_chamberhttp://en.wikipedia.org/wiki/Ion_chamberhttp://en.wikipedia.org/wiki/Ion_chamberhttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Photodiodehttp://en.wikipedia.org/wiki/Photodiodehttp://en.wikipedia.org/wiki/Photodiodehttp://en.wikipedia.org/wiki/Helical_cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Helical_cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Helical_cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/X-ray_tubehttp://en.wikipedia.org/wiki/X-ray_tubehttp://en.wikipedia.org/wiki/X-ray_tubehttp://en.wikipedia.org/wiki/Electron_beam_tomographyhttp://en.wikipedia.org/wiki/Electron_beam_tomographyhttp://en.wikipedia.org/wiki/Electron_beam_tomographyhttp://en.wikipedia.org/wiki/File:CT_Scan_of_Dale_Mahalko's_brain-skull.jpghttp://en.wikipedia.org/wiki/File:CT_Scan_of_Dale_Mahalko's_brain-skull.jpghttp://en.wikipedia.org/wiki/File:CT_Scan_of_Dale_Mahalko's_brain-skull.jpghttp://en.wikipedia.org/wiki/File:CT_Scan_of_Dale_Mahalko's_brain-skull.jpghttp://en.wikipedia.org/wiki/Electron_beam_tomographyhttp://en.wikipedia.org/wiki/X-ray_tubehttp://en.wikipedia.org/wiki/Helical_cone_beam_computed_tomographyhttp://en.wikipedia.org/wiki/Photodiodehttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Ion_chamberhttp://en.wikipedia.org/wiki/Cesium_iodidehttp://en.wikipedia.org/wiki/Photomultiplier_tubehttp://en.wikipedia.org/wiki/Scintillation_detectorhttp://en.wikipedia.org/w/index.php?title=X-ray_computed_tomography&action=edit&section=16


14/20

CT scanner with cover removed to show the principle of operation

CT is used inmedicineas a diagnostic tool and as a guide for interventional procedures.Sometimes contrast materials such asintravenousiodinatedcontrast are used. This is useful tohighlight structures such as blood vessels that otherwise would be difficult to delineate from their

surroundings. Using contrast material can also help to obtain functional information about

tissues.

Once the scan data has been acquired, the data must be processed using a form oftomographic

reconstruction, which produces a series of cross-sectional images. The most common technique

in general use isfiltered back projection, which is straight-forward to implement and can becomputed rapidly. In terms of mathematics, this method is based on theRadon transform.

However, this is not the only technique available: the original EMI scanner solved the

tomographic reconstruction problem bylinear algebra, but this approach was limited by its highcomputational complexity, especially given the computer technology available at the time. More

recently, manufacturers have developed iterative physical model-based expectation-

maximization techniques. These techniques are advantageous because they use an internal modelof the scanner's physical properties and of the physical laws of X-ray interactions. By contrast,

earlier methods have assumed a perfect scanner and highly simplified physics, which leads to anumber of artifacts and reduced resolution - the result is images with improved resolution,

reduced noise and fewer artifacts, as well as the ability to greatly reduce the radiation dose incertain circumstances. The disadvantage is a very high computational requirement, which is at

the limits of practicality for current scan protocols.

Pixelsin an image obtained by CT scanning are displayed in terms of relativeradiodensity. Thepixel itself is displayed according to the meanattenuationof the tissue(s) that it corresponds to

on a scale from +3071 (most attenuating) to -1024 (least attenuating) on the Hounsfield scale.Pixelis a two dimensional unit based on the matrix size and the field of view. When the CT slice

thickness is also factored in, the unit is known as aVoxel, which is a three-dimensional unit. The

phenomenon that one part of the detector cannot differentiate between different tissues is called

the "Partial Volume Effect". That means that a big amount of cartilage and a thin layer ofcompact bone can cause the same attenuation in a voxel as hyperdense cartilage alone. Water has
http://en.wikipedia.org/wiki/Medicinehttp://en.wikipedia.org/wiki/Medicinehttp://en.wikipedia.org/wiki/Medicinehttp://en.wikipedia.org/wiki/Intravenoushttp://en.wikipedia.org/wiki/Intravenoushttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Tomographic_reconstructionhttp://en.wikipedia.org/wiki/Tomographic_reconstructionhttp://en.wikipedia.org/wiki/Tomographic_reconstructionhttp://en.wikipedia.org/wiki/Tomographic_reconstructionhttp://en.wikipedia.org/wiki/Filtered_back_projectionhttp://en.wikipedia.org/wiki/Filtered_back_projectionhttp://en.wikipedia.org/wiki/Filtered_back_projectionhttp://en.wikipedia.org/wiki/Radon_transformhttp://en.wikipedia.org/wiki/Radon_transformhttp://en.wikipedia.org/wiki/Radon_transformhttp://en.wikipedia.org/wiki/Linear_algebrahttp://en.wikipedia.org/wiki/Linear_algebrahttp://en.wikipedia.org/wiki/Linear_algebrahttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wiktionary.org/wiki/attenuationhttp://en.wiktionary.org/wiki/attenuationhttp://en.wiktionary.org/wiki/attenuationhttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Voxelhttp://en.wikipedia.org/wiki/Voxelhttp://en.wikipedia.org/wiki/Voxelhttp://en.wikipedia.org/wiki/File:Ct-internals.jpghttp://en.wikipedia.org/wiki/File:Ct-internals.jpghttp://en.wikipedia.org/wiki/File:Ct-internals.jpghttp://en.wikipedia.org/wiki/File:Ct-internals.jpghttp://en.wikipedia.org/wiki/Voxelhttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Hounsfield_scalehttp://en.wiktionary.org/wiki/attenuationhttp://en.wikipedia.org/wiki/Radiodensityhttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Linear_algebrahttp://en.wikipedia.org/wiki/Radon_transformhttp://en.wikipedia.org/wiki/Filtered_back_projectionhttp://en.wikipedia.org/wiki/Tomographic_reconstructionhttp://en.wikipedia.org/wiki/Tomographic_reconstructionhttp://en.wikipedia.org/wiki/Iodinehttp://en.wikipedia.org/wiki/Intravenoushttp://en.wikipedia.org/wiki/Medicine


15/20

an attenuation of 0Hounsfield units(HU), while air is -1000 HU, cancellous bone is typically

+400 HU, cranial bone can reach 2000 HU or more (os temporale) and can cause artifacts. Theattenuation of metallic implants depends on atomic number of the element used: Titanium

usually has an amount of +1000 HU, iron steel can completely extinguish the X-ray and is,

therefore, responsible for well-known line-artifacts in computed tomograms. Artifacts are caused

by abrupt transitions between low- and high-density materials, which results in data values thatexceed the dynamic range of the processing electronics.

Contrast mediumsused for X-ray CT, as well as forplain film X-ray, are calledradiocontrasts.

Radiocontrasts for X-ray CT are, in general, iodine-based.[26]

Often, images are taken both with

and without radiocontrast. CT images are calledprecontrastor native-phase images before anyradiocontrast has been administrated, andpostcontrastafter radiocontrast administration.

[27]

[edit] Three-dimensional reconstruction

Because contemporary CT scanners offerisotropicor near isotropic, resolution, display of

images does not need to be restricted to the conventional axial images. Instead, it is possible for asoftware program to build a volume by "stacking" the individual slices one on top of the other.

The program may then display the volume in an alternative manner.[28]

[edit] Multiplanar reconstruction

Typical screen layout for diagnostic software, showing one 3D and three MPR views

Multiplanar reconstruction(MPR) is the simplest method of reconstruction. A volume is built bystacking the axial slices. The software then cuts slices through the volume in a different plane

(usually orthogonal). As an option, a special projection method, such asmaximum-intensityprojection(MIP) or minimum-intensity projection (mIP), can be used to build the reconstructed

slices.

MPR is frequently used for examining the spine. Axial images through the spine will only show

one vertebral body at a time and cannot reliably show the intervertebral discs. By reformatting
http://en.wikipedia.org/wiki/Hounsfield_unitshttp://en.wikipedia.org/wiki/Hounsfield_unitshttp://en.wikipedia.org/wiki/Hounsfield_unitshttp://en.wikipedia.org/wiki/Contrast_mediumhttp://en.wikipedia.org/wiki/Contrast_mediumhttp://en.wikipedia.org/wiki/Radiographyhttp://en.wikipedia.org/wiki/Radiographyhttp://en.wikipedia.org/wiki/Radiographyhttp://en.wikipedia.org/wiki/Radiocontrasthttp://en.wikipedia.org/wiki/Radiocontrasthttp://en.wikipedia.org/wiki/Radiocontrasthttp://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-25http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-25http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-25http://en.wikipedia.org/wiki/X-ray_computed_tomography#ci

Documents

A Medical Device is a Product Which is Used for Medical Purposes in Patients