Radiology Lecture

By Dr Kebede(MD,Radiologist)

Learning objectives:

• Understand sources of radiation exposure• Discuss Ethical, professional and legal issues of

radiation exposure• Understand mechanisms of protecting patients and

the public from inappropriate radiation exposure• Discuss medical application of radiation and common

diagnostic imaging modalities • Discuss radiological approach to common diagnostic

imaging modalities

Mode of Assessment

• Progressive assessment (attendace,active participation)….25%

• Written exam : 75%

Responsibility of the students

• Attendance : 100%• Attentiveness • Active participation

Sources of radiation

Natural (70-85%,2.4 milisielvert/year)

• Inhalational(Radon gas)• Radionuclide from rock• Ingestion• Cosmic radiation

Man-made(15-30%,0.6milisilviert/year)

• Diagnostic medical exposure

• Atmospheric nuclear testing• Occupational exposure

Radiation exposure of the public

• 70-85% (2.4msV)natural background radiation• 15-30% (0.6msv)medical radiation exposure• Overall exposure : 3msV /Year• CT scan contributes for 4% of all diagnostic

imaging modality but shares 40% of all medical radiation exposures

Hazards of radiation exposure

• Carcinogenesis• Teratogenesis• Abortion• Burn

NB: Stochastic vs. Deterministic effects

Life time risk of fatal cancer after diagnostic medical radiation exposure

Guideline while imaging a patient

• A useful investigation is one in which the result - positive or negative – will alter clinical management and/or add confidence to the clinician's diagnosis.

• Significant number of radiological investigations do not fulfill these aims hence causing inappropriate patient radiation exposure.

Major causes of inappropriate patient exposure

1. Repeating investigations2. Investigation when results are unlikely to affect

patient management3. Investigating too often4. Doing the wrong investigation5. Failing to provide appropriate clinical information

and questions that the imaging investigation should answer.

6. Over-investigating

Mechanism to protect patients and the public

• Justification of the procedure• Optimization of a procedure• Dose reduction techniques

The field of Radiology and Imaging

• Young dynamic field on continuous changes and improvement

• Importance of radiology and its value for modern medicine

• Futures and Advances in Imaging• Risks ,medico-legal issues and public concerns

What did radiology Add to medicine?

• Imaging difficult organs(organs like Brain,mediastinum,retroperitoneum,.)

• Better surgical planning • Staging cancers• Interventional radiology• radiotherapy

Imaging Modalities• Radiation emitting

modalities– Radiographs (analogue,

computed Radiograph and digital)

– Fluoroscopy– Mammography– Computed Tomographic

(CT) Scan– Nuclear medicine

Imaging

• Non-Radiation emitting modalities

• Ultrasound • Magnetic Resonance

Imaging(MRI)

Mode of imaging

• Anatomical imaging– Radiographs– Mammography – Ultrasound – CT scan– MRI

• Functional Imaging– Nuclear medicine

(PET,SPECT)– Functional MRI

• Combined – PET-CT– PET-MRI

Conventional radiographs

• .

Fluoroscopy

CT scan

• . • .

Radiographic densities

• Air : blackest on a radiograph• Fat, which is shown in a lighter shade of gray than

air• Soft tissue or fluid (because both soft tissue and

fluid appear the same on conventional radiographs, it’s impossible to differentiate the heart muscle from the blood inside of the heart on a chest radiograph)

• Calcium (usually contained within bones)• Metal : appears the whitest on a radiograph

MRI

Systematic approach to common radiographs

By Kebede(MD,Radiologist)

LECTURE -2

Systematic Approach to CXR

Technique :

• Standard : PA and lateral• Critically ill patients, pediatrics: AP/SupineIndications : – Persitenent cough > 2weeks– In working up Complications of pneumonia – Congestive Heart failure, pulmonary edema– Pulmonary Thromboembolism– Lung cancer and ,metastatic work up– Preoperative work up– Follow up of treatment

1. Assessing Technical adequacy

• Labeling : Identification ,Technique, right/left, Date• Inspiratory /Expiratory : anteriorly 6 ribs, posteriorly

10 ribs has to be seen• Rotation : medial ends of the clavicle should be at

equidistance from the spinous process/ 1/3rd of the cardiac shadow should be in the right hemi chest and 2/3rd should be in the left hemi chest

• Penetration : above 4 thoracic vertebrae should be visualized…..underpenetrated if not visualized and over penetrated if lower vertebrae are visualized.

UNDER PENETRATED

OVER PENETRATED

NORMAL

APPA

AP film : apparent magnification of the cardiac and mediastinal outline is seen

ANTERIOR RIBS

POSTERIOR RIBS

Inspiratory Expiratory

Drawbacks of expiratory film

• cardiomegaly• Abnormal contour of the aorta and• patchy opacification in both lower zones.

Drawbacks of Underpenetrated film

• apparent cardiomegaly• apparent hilar abnormalities• apparent mediastinal contour abnormalities• the lung parenchyma tends to appear of

increased density, i.e. ‘white lung’.

….technical adequacy

• Field of view: should include the lung apices and the costophrenic angles

• Others: breast shadow should be outside of the lung field, foreign bodies like necklace should be removed

• Hence , before reading Chest film its technical adequacy has to be assessed whether it is adequate to read or not since technically inadequate film may mask or overcall findings and mislead to patient mismanagement.

INSIDE –OUT-APPROACH

• Air ways– Trachea : • Location : Central/slight shift to the right• Size : 13mm-23mm in females,15mm-27mm in males• Lumen: air field• Carinal angle : acute angle,72 degrees• Para tracheal strip < 4mm

Right partracheal strip

• Hilum

– Location : left is always higher than the right– Density : symmetric and concave outward; Contributed by :

pulmonary artery and veins,lymphatics not the air ways• Pulmonary vasculatures:

– Are the only white branching linear opacities in lung field which fade in peripheral 1/3rd of the lung field/first intercostal space

– In PA film lower lung zones are more vascularized than the upper lung zones

– If there is at least equalization of vascular diameter in upper and lower zone there is vascular redistribution or cephalization

….continued

• Lung Fields: – Compare both lungs zone by zone – Upper lung zone is more ventilated than the lower

lung zone– Upper lung zone : up to 2nd intercostal space– Mid lung zone : between 2nd and 4th intercostal

space– Lower lung zone : below 4th intercostal space

Cont…..

• Cardiac and mediastinal silhouette• Location : Central • Shape• Size : <50% in adult on PA ,<60% in pediatrics and

supine films• Outlines: Its borders should be well outlined

• Diaphragm • Well outlined• Dome shaped• Acute costophrenic angles

….cont

• Rib cage and soft tissue– Bones : osteolytic or sclerotic changes, missing

ribs, deformity– Soft tissue : swelling,gas,calcifications ,nodules,..

• Hidden Areas– Sub diaphragmatic areas,retrocardiac

areas,paratracheal areas and peripheral lung fields

Common terminologies• Opacification : increased density in the lung field• Luncency : increased blackness/transradiancy• Consolidation : ill-defined opacity with internal branching

tubular radiolucent areas representing patent terminal bronchioles……air bronchogramme .

• Collapse : well defined increased opacity due to blocked air ways; could be segemental,lobar,total…..no air bronchogramme.

• Reticulations : linear radio-opaque shadows• Nodules : discrete ,round radio-opaque shadows < 3cm• Mass: well defined radio-opacity >3cm

..cont

• Blebs : subpleura air containing lesions < 1cm in diameter having thin wall

• Pneumatocele: air containing lesions < 1cm in diameter having thin wall measuring <1mm

• Bullae : air containing lesions >1cm in diameter having thin wall <1mm

• Cavity : air containing lesions >1cm in diameter having thick wall <1mm(active infection >3mm,air fluid level in the cavity and adjacent consolidation)

…cont

• Silhouette sign : Loss of the normal radiologic definition/contrast between two adjacent structures

Consolidation with air-bronchogramme

REVERSED BATWING

• When the periphery of the lung is affected and the central areas are spared

Atelectasis with well defined increased opacity

Atelectasis

mass

Nodule

Reading assignment

• How to approach and differentiate air space VS. Interstitial lung Parenchymal diseases on chest X RAY (Learning radiology recognizing the basics chapter 5 and Radiology Assistant Chest X-Ray - Lung disease Four-Pattern ApproachInternet)

Lecture -3

Approach to spine X ray

Approach to cervical spine x ray

• Technique : AP and lateral• Supplementary views: Open mouth

view ,flexion and extension viewsTechnical adequacy: Skull base and C7/T-1

Junction should be includedSystematic Approach : ABCS

NORMAL : LATERAL

NORMAL : AP

NORMAL OPEN MOUTH VIEW

A-Alignment(assed on lateral film)

• Line 1 is in the prevertebral soft tissue……..10mm anterior to C-1 ,5-7mm between C-2-C-4, and 22mm between C-5-C-7. It should have smooth contour.

• Line 2 follows the anterior vertebral bodies and should be smooth and uninterrupted.

• Line 3 is similar to the anterior vertebral body line (line 2) except that it connects the posterior vertebral bodies.

• Interruption of the anterior and posterior vertebral body line is a sign of a serious injury

Cont…..

• Line 4, called the spino-laminal line, connects the posterior junction of the lamina with the spinous processes.

• The spinal cord lies between lines 3 and 4; therefore any offset of either of these lines could mean that a bony structure is impinging on the cord.

• Severe neurologic deficits can result from very little force against the cord, and any bony structure lying on

…cont

• Line 5 is not really a line so much as a collection of points—the tips of the spinous processes

• After visually inspecting these five lines on the lateral C-spine, inspect the C1–2 area a little more closely. Make certain that the anterior arch of C1 is no greater than 2.5 mm from the dens in adults and 5mm in children.

B-bones

• Height : Anterior and posterior vertebral body height should be equal

• Size : progressively increase downwards• Cortical outline should be smooth• End plates : smooth• Density (normal trabecullar pattern ,accentuated

trabecullar pattern….osteoporosis)• Look for any osteolytic or sclerotic changes• Look for osteophytes

C-Cartillage/Disc spaces

• The disc spaces are examined next to check for any inordinate widening or narrowing, either of which could indicate an acute traumatic injury.

• If a disc space is narrowed, it will usually be secondary to degenerative disease. Make certain that associated osteophytosis and sclerosis are present.

• Look also for facet joints and neural foramina

Vertebral columns

Stable Vs Unstable Fracture

• Stable : Fracture involving only one column• Unstable fracture : Fracture involving more

than one column

Terminologies

• Spondylosis : bony Overgrowth over the vertebral bodies(osteophytosis)

• Spondylolisthesis : sliding of vertebral bodies over one another(Grade -1 < 25% of the vertebrae has slided over, Grade 2 25-50%,Grade 3 50-75% and Grade 4 mores than 75% of the vertebral body is sliding over the inferior)

• It could be posterior or anterior• Spondylolisis : Fracture of the vertebrae

Common Indications for cervical spine x ray

• Trauma• Radiating neck pain• Infection(vertebral and soft tissue)• Metastasis• Degenerative changes• Neoplastic conditions• Upper air way obstruction• Foreign body,..

Thoracic and Lumbar spine

Technique : AP and lateral Normal vertebral curvature in adults• Cervical and lumbar : lordosis• Thoracic and sacral spine : Kyphotic• 5-lines are used in cervical spine only • The size of vertebral body and the height of

disc spaces will gradually increase downwards• Otherwise systematic approach is the same

Lumbar spine : AP

NB:

• For systematic approach of thoracic and lumbar spine X ray please refer emergency radiology page 328-329

• Spine Tuberculosis is the most common musculoskeletal tuberculosis

• Thoraco-lumbar junction is the most common site• Paravertebral collection/abcesses with

calcification is pathognomonic for Tuberculoses spondylodiscitis

Role of MRI in spine

• MRI is superior for evaluation of degenerative vertebral and disc diseases, disc prolapse ,for assessing central canal and neural foraminal stenosis, for diagnosis of spondylodiscitis

• MRI has also superior efficacy for spinal cord neoplasms,infection and inflammatory condition of the spine, and for assessing spinal cord injury and compression.

Role of CT in spine

• Gold standard for bony lesion• For assessing trauma• For assessing Bone

neolasms(Primary/secondary)• Assessing Osteoporosis

Lecture -4

Systematic approach to extremity radiographs

Indication

• Infection • Inflammatory conditions like rheumatoid

arthritis• Bone neoplasm's

Systematic approach: ABCS

• A-Adequacy and alignment– View : Atleast two views – Areas of interest should be included– Adequately penetrated film– Normal alignment in specific region

B-Bone

• Cortex : have smooth cortical outline ,fracture lines

• Normal medullary cavity• osteolytic or sclerotic changes• Density : normal or osteoporotic

C-Cartillage /joint

• Articulating surface : smooth outline with no irregularity

• Joint space : look for asymmetric widening or narrowing

• Look for any intra-articular foreign bodies/loose bodies

S-Soft tissue

• Look for swelling• Fat planes….obliteration/displacement• Gas in soft tissue(indicates gas forming

infections/abcesses), foreign bodies

Imaging modalities of choice

• MRI and Nuclear medicine scan : detect osteomyelits at earlier stage(in the first 3 days)

• Conventional Radiographs: There is radiological lag of 10days -2weeks for osteomyelits

• MRI : Is helpful to know the extent of bone and soft tissue involvement in sarcomas of the bone and soft tissue

• CT : Better for assessing and grading fracture• Ultrasound : cellulites ,soft tissue abscess, Pyomyositis,

joint effusion

LECTURE -5

Plain Abdominal X ray ,normal and abnormal bowel gas distribution, signs of extra luminal gas…well discussed in class

Plain Abdominal X ray

• Standard : Erect plain abdominal X ray• Other views: Supine and cross table lateral

decubitus

Systematic approach to plain abdominal x ray

• Look for normal bowel gas distribution• Look for abnormal bowel gas distribution• Look for abnormal soft tissue density• Look for abnormal calcifications

Normal bowel gas distribution

• Stomach : air is always seen except in NG tube decompression or excessive vomiting

• Small bowel : 2-3 non-dilated bowel loops• Large bowel: Normally seen in rectum and

sigmoid

Abnormal bowel gas distribution

• The presence of > 3 air fluid levels in small bowel

• The presence of one air-fluid level in large bowel is abnormal

• Absence of gas in the rectum• Dilated bowel loops(>3cm in small bowel,>6cm

in large bowel and > 9cm in cecum==rule of 3)• Signs of extralumnal gas.

References

• Learning radiology recognizing the basics 3rd edd

• Emergency radiology 1st edd• Fundamentals of skeletal radiology 4th edd• Internet : Radiology Assistant