MODULE 11 -Radiation Protection in Medical Imaging

These flashcards cover important concepts regarding radiation protection in medical imaging as outlined in the lecture notes.

What Canadian safety code outlines radiation protection in medical imaging facilities?

Safety Code 35 by Health Canada.

Who was the first to recommend x-ray shielding and when?

Dr. Rollins, a Boston dentist, in 1898.

What were Dr. Rollins' 3 key radiation protection recommendations?

1. Wear radiopaque glasses 2. Enclose the x-ray tube 3. Irradiate only the necessary region

What is the primary purpose of facility design according to Safety Code 35?

To minimize radiation exposure to patients, staff, and the public.

What are the three factors that determine shielding requirements in a facility?

Maximum workload, occupancy factor, and use factor.

What is a primary protective barrier?

A shield designed to block the direct x-ray beam (e.g., wall behind upright bucky, floor under table bucky).

What is a secondary protective barrier?

A shield that blocks scatter and leakage radiation (e.g., control booth, ceiling, doors).

Why should the x-ray tube never be aimed at the control booth?

To minimize occupational radiation exposure, as the control booth is a secondary barrier.

What kind of shielding is required for angiographic and radioscopic equipment?

Only secondary shielding.

What act must all diagnostic x-ray equipment comply with in Canada?

The Radiation Emitting Devices Act.

What is the difference between the Radiation Emitting Devices Regulations and Medical Devices Regulations?

Radiation Emitting Devices Regulations cover safety features related to radiation; Medical Devices Regulations cover all other equipment standards.

List at least four equipment requirements for imaging safety.

1. Radiation warning signs 2. Indicator lights 3. Beam filter and shield 4. Loading factor indicators 5. Controlling timers

What is required for radiographic equipment performance?

Reproducibility and linearity, irradiation switch, beam-limiting device, accurate loading and alignment, AEC (Automatic Exposure Control).

What are two safety features required in radioscopic (fluoroscopic) equipment?

Protective shielding and last-image hold.

What are CR imaging components that require maintenance?

CR plates and cassettes, electronic display devices, PACS system, teleradiology systems.

What are monthly tests for digital display quality assurance?

Geometric distortion, luminance, resolution tests.

What is a radiation protection survey?

An inspection by a qualified expert to assess safety and compliance of an imaging facility.

What should be considered when disposing of x-ray equipment?

Contact the manufacturer and check for recyclability due to components like PCBs (polychlorinated biphenyls).

What do PCBs found in x-ray tubes pose a risk for?

Diseases such as cancer.

What is the purpose of shielding walls in a radiology facility?

To protect people in surrounding rooms from scatter radiation.

List the 9 general requirements that must be met by all radiographic and radioscopic equipment.

warning signs, markings, mechanical stability, indicator lights, indication of loading factors, irradiation control, controlling timer, x-ray tube shielding, x-ray beam filtration

What would cause excessive x-ray tube drift or vibration during operation of radiographic or radioscopic equipment?

poor mechanical stability

What device would allow initiation and termination of x-ray production?

Irradiation control

What is the purpose of x-ray beam filtration?

X-ray Beam Filtration--There must be radiation-absorbing filters that provide a degree of attenuation

What is the difference in how AEC is evaluated between film based systems and digital systems?

For film-based systems, the optical density of the films is measured for reproducibility while for digital systems, the manufacturers recommendations should be followed.  Ideally, the variation for digital systems should be within 20%

TRUE OR FALSE: Minimum Irradiation Time Capability--The controlling timer or automatic exposure control device must have a minimum irradiation time capability of 1/60 s or the time required to deliver a current-time product of 5 mAs, whichever is greater.

TRUE

Where should the location of the focal spot be clearly indicated?

The location of the focal spot must be clearly and accurately marked on the X-ray tube housing.

For radioscopic equipment, what technical parameters must be continuously displayed?

x-ray tube voltage and x-ray tube current

What is the purpose of a chronometer?

a chronometer indicates the amount of time equipment has been emitting X-rays and can be reset to zero or any other selected value.

TRUE OR FALSE: The radiation resulting from the transmission of the X-ray beam through, must not exceed an air kerma rate of 2 mGy/h for an entrance air kerma rate of 1 Gy/min

TRUE

What is the minimum attenuation equivalent for protective lead aprons where the peak xray tube voltage is 100 kv or less?

0.25 mm of lead, at 100 kV or less

What is the minimum attenuation equivalent for protective lead aprons where the peak xray tube voltage is greater than 150 kV?

0.5mm At 150kV or greater

During interventional procedures, what lead equivalency is required for thyroid shields?

0.50 mm Pb are recommended.

TRUE or FALSE: Protective gonad shields for patients must have a lead equivalent of at least 0.25 mm Pb and should have a lead equivalent thickness of 0.5 mm at 150 kVp

TRUE

What is the lead equivalency required of ceiling mounted lead acrylic screens and moveable shields?

0.50mm Pb

What is a radiation protection survey?

A survey intended to demonstrate that the X-ray and auxiliary equipment function properly and according to applicable standards

Who performs a radiation protection survey?

The expert is an individual who is qualified by education and experience to perform advanced or complex procedures in radiation protection

For a new facility, what is the radiation protection surveyor assessing?

Thickness of lead, degree of overlap between lead sheets and thickness & density of leaded glass used in viewing windows