International Atomic Energy Agency Medical exposure in radiology: Scope and responsibilities Module...

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Medical exposure in radiology:Medical exposure in radiology:Scope and responsibilitiesScope and responsibilities

Module VIII.1 - Part 1 : General principles

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IntroductionIntroduction

• We will introduce briefly in this lecture the main modalities using ionizing radiation in a Medical Imaging Department

• And who are the “actors” using these imaging modalities ?

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TopicsTopics

1. What IS radiology ? And the different modalities.

2. The team of professionals

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OverviewOverview

• In this presentation we will present the scope of medical imaging, the terminology used, the variety of modalities (from plain radiography to CT), and the complementarity with other imaging techniques

• The medical physicist as expert plays an important roel in radiation protection

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Topic 1: what is radiology?Topic 1: what is radiology?

An Introduction to Radiology: purpose, sub-modalities and basic terminology

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Topic 1: contentTopic 1: content

• What is radiology and who performs it

• Some basic terminology and equipment

• Different modalities overview• Plain radiography

• Fluoroscopy

• Angiography

• Digital subtraction angiography (DSA)

• Computed tomography (CT)

• Complementarity of methods: • CT and MRI

• Isotopes: Nuclear Medicine

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What IS Radiology ?What IS Radiology ?

(from EUR16260)

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Radiology is…Radiology is…

• Study of images of the human body

• Start: use of X Rays and photographic film

• Additional: use of X Rays in therapy

• Now: separate specialty and department

• Today variety of tools for imaging

• Creating images computer assisted: CT

• Some using no ionizing radiation: US, MRI

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““Radiology” in this course series…Radiology” in this course series…

• Restricted to the use of X Rays (Ionizing radiation)

• Plain radiography: static

• Fluoroscopy: dynamic

• Angiography: use of contrast material

• Computed tomography

• Specific applications:• Mammography: breast cancer detection

• Pediatric radiology: from newborn to grown-up

• Aid to other specialties: Interventional radiology

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Plain radiographyPlain radiography

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Plain RadiographyPlain Radiography

• Obtained by exposing patient to X Rays

• Image is basically a shadow of parts of patient absorbing or blocking X Rays

• Image is collected on• Photosensitive film

• A digital imaging plate

• A fluoroscopic system

with cassette holder

• Image is a “photographic negative”• Darker regions have less absorbed X Rays

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Plain radiography: example of equipmentPlain radiography: example of equipment

High voltagegenerator

Tube housing And diaphragm

Movable patient “couch”

Film cassetteholder

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FluoroscopyFluoroscopy

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FluoroscopyFluoroscopy

One image of a “life” sequence

Colon

White areas:Barium,

contrast medium

Black areas: air

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FluoroscopyFluoroscopy

• X Ray transmitted trough patient

• Out-beam strikes fluorescent screen

• Part of an Image Intensifier system

• Coupled to a television camera

• Radiologist can watch the images “live” on TV-monitor; images can be recorded

• Fluoroscopy often used to observe digestive tract• Upper GI series, Barium Swallow

• Lower GI series Barium Enema

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The Image Intensifier: The Image Intensifier: basic element of the fluoroscopy equipmentbasic element of the fluoroscopy equipment

Input fluorescent

screen

In vacuum electronic amplification system

Output window

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Fluoroscopy room equipmentFluoroscopy room equipment

Typical Fluoroscopy equipment, with “over-coach” tube, viewed from above (Philips)

I I and TV camera under patient’s table

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C-arm equipmentC-arm equipment

• Ability to maneuver c-arm around patient without moving him

• Often used as “mobile” unit• Critical care units

• In room examination

• Modern units allow fluo + radiography

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Mobile unitMobile unit

Parking conditions

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AngiographyAngiography

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Angiography imagesAngiography images

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What is angiographyWhat is angiography

• Invasive procedure• Injection into patient of radio-opaque

substance (“Dye” or “Contrast Agent”)

• Injection by small tube into vein or artery

• The radio-opaque material• Blocks X Rays

• Gives shadow of injected vessels

• Reveals shape of artery/vein

• Diagnosis of obstruction, narrowing (Stenosis)

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Digital Subtraction Angiography or DSADigital Subtraction Angiography or DSA

Digital: allows subtraction, image manipulationTwo images with different calculation algorithms

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What is DSA?What is DSA?

• Subtraction: removes non-essential structures in the image

• Combining mathematically pre- and post-contrast images

• Noisier, but improves visibility of important structures

• DSA was first full digital based fluoroscopic imaging procedure: high spatial resolution not necessary

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Computed TomographyComputed Tomography

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Computed TomographyComputed Tomography

• CT- Scan:• Computer tomography

• CAT-scan:• Computer axial

tomography

• Gives sectional, in depth or 3-D information

• CT supersedes “linear tomography”

or

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What is CT ?What is CT ?

• Spinning X Ray source and detectors around patient

• Attenuation data collected from multiple angles

• Computer processes these data

• A reconstructed image is presented on screen

• These images: “cuts”, “slices”, “sections”

• Newer generation: helical/spiral scan, 3-D data

• Problem of overlap of shadows is solved

• CT can be performed “plain” or after injection of “contrast agent”

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Complementarity with other modalitiesComplementarity with other modalities

Magnetic Resonance Imaging (MR or MRI)

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Magnetic Resonance ImagingMagnetic Resonance Imaging

Two images obtained with (different) MRI techniques, compared to CT-slice(DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOR)

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Magnetic Resonance ImagingMagnetic Resonance Imaging

• No use of X Rays or other type of Ion. Radiation

• Magnetic field “lines-up” protons

• Coils with high frequency pulse knocks the out of alignment

• Radiofrequency antennas “listen” to the emitted resonance signals

• Resonance signals are treated by computer, creates 3-d information

• “Cuts” or “slices” presented similar to CT, but information collected different/complementary

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Historical picturesHistorical pictures

An X Ray examination room (Mayo Clinic circa

1925)

Original EMI CT head scanner an 80 x 80-matrix head CT

image obtained with it (1973)

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Historical Pictures: radiology and… risksHistorical Pictures: radiology and… risks

Radiograph of the hand of Mrs. Roentgen

1903: first radiation risk reports[From R F Mould, A Century of X-Rays…]

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Summary of Topic 1Summary of Topic 1

• Radiology serve the diagnosis of patients

• Uses different modalities, mainly involving ionizing radiation: X Rays

• Plain radiography gives static projection image

• Fluoroscopy gives dynamic images

• Contrast agents improve visibility, used e.g. in angiography

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Summary of Topic 1 Summary of Topic 1 (cont.)(cont.)

• Digital systems allow subtraction of images, enhancing visibility (DSA)

• CT techniques allow 3-d reconstruction

• Nuclear medicine and MRI images are complementary to X Ray images

• From early beginnings radiology included radiation risks

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Topic 2: the professionalsTopic 2: the professionals

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The team…The team…

• Medical practitioner: the Radiologist• M.D. with training interpretation of medical images

• Interprets the images to establish diagnosis

• Radiographer (radiological technologist)• Staff member trained in positioning patient and

optimal use of equipment for image quality and radiation protection

• Radiodiagnostic Physicist as qualified expert• Dose optimization

• Optimizing of imaging protocols

• Link with “outside” of department• The referring M. D.

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BSS RequirementBSS Requirement

As per BSS II.2, registrants and licensees should ensure that for diagnostic uses of radiation, the imaging and quality assurance requirements of the Standards be fulfilled with the advise of a qualified expert in radiodiagnostic physics

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Clinical responsibilityClinical responsibility

•Responsibility regarding individual medical exposures attributed to a practitioner

•This includes:

•justification;

•optimization;

•clinical evaluation of the outcome;

•cooperation with other specialists and the staff, as appropriate

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Clinical responsibility Clinical responsibility (2)(2)

•Practical aspects: •obtaining information of previous

examinations;

•providing existing radiological information and/or records to other practitioners and/or prescribers;

•giving information on the risk of ionizing radiation to patients and other individuals involved

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The Roles, Responsibilities and Status of The Roles, Responsibilities and Status of the Radiodiagnostic Physicistthe Radiodiagnostic Physicist

Two categories

• One category : of physicists working as teachers and scientists in universities, as researchers in industrial laboratories, in governmental research institutions

• The second category: physicists working in a clinical environment, in the hospital• Names: "medical physicist", "clinical physicist", "hospital

physicist“ are used in different countries

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Radiodiagnostic Physicist: definitionRadiodiagnostic Physicist: definition

• Has or might have an influence on the diagnosis and/or treatment and safety of patients, or their decisions might have consequences for the performance of diagnostic, treatment and safety procedures in hospital care.

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Radiodiagnostic physicist: responsibilitiesRadiodiagnostic physicist: responsibilities

• The main responsibility of the Radiodiagnostic physicist is to provide a high standard of service in the hospital.… He is a member of a team of personnel responsible for diagnosis and treatment of patients. The physicist wil have an influence on the diagnosis, treatment and safety procedures for the patient and thus his decisions will have consequences for the patient. As his decisions are based on his competence, a competence not found elsewhere he should be fully responsible for his work [ from EFOMP]

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More Responsibilities of the More Responsibilities of the RadiodiagnosticRadiodiagnostic Physicist Physicist

• High standard of service

• Standardisation and calibration of medical physical equipment

• Safety of physical methods used in routine clinical applications (with medical staff)

• Research and in the development

• Providing education and training in applied physics for doctors, nurses, medical technical assistants

• Recognised by the national health authorities

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Ionizing radiation: Radiodiagnostic Ionizing radiation: Radiodiagnostic Physicist as the qualified expertPhysicist as the qualified expert

• Man-made contribution to the radiation exposure of human beings primarily due to the use of Ionizing Radiation and radioactive substances in medicine.

• Radiodiagnostic Physicist will act as the “Qualified Expert in Radiation physics”

• Responsible for radiation protection of the patient and the staff in radiological department

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The Role of the Qualified Expert inThe Role of the Qualified Expert in RadiodiagnosticRadiodiagnostic Physics Physics

• Dosimetry of the equipment beams

• Lay down and supervise the Quality Assurance programme

• Surveillance with respect to radioprotection• Public, staff, …

• Reduce dose to patients, keeping in mind the required image quality

• Choose equipment for radiation protection

• Give advice on purchase of diagnostic equipment with respect to image quality and radiation protection

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What we learnedWhat we learned

• To become familiar with the multiple imaging modalities in a radiological department

• Each modality requires specific equipment

• In radiation protection (patient or staff) the medical physicist as a qualified expert plays a central role

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Where to get more information?Where to get more information?

• The Physics of Diagnostic Imaging, David J. Dowsett, Patrick A. Kenny and R. Eugene Johnston, Chapman & Hall Medical, ISBN 0-412-40170-1

• International Basic Safety Standards for Protection Against Ionizing Radiation and for the Safety of Radiation Sources. 115, Safety Standards. IAEA, February 1996.

• ICRP 73. Radiological Protection and Safety in Medicine. Annals of the ICRP, 26(2), 1996.

• Qualified Expert in Radiophysics,The European Federation of Organisations for Medical Physics, Policy Statement 3

• Role and Responsibilities of Medical Physicists in Radiological Protection of Patients, Azam Niroomand-Rad, Ph D; See: IOMP Website