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Questions and Answers
The x-ray beam may be on for a relatively short time during C-arm fluoroscopy.
False
Radiologic personnel should always exceed 50 mSv/yr (5000 mrem/yr) of radiation exposure per year.
False
Average exposures in most facilities are less than 1 mSv/yr (100 mrem/yr).
False
The maximum permissible dose (MPD) was the dose of radiation that would be expected to produce significant radiation effects.
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The dose limit (DL) is only specified for whole-body exposure.
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The whole-body DL of 20 mSv/yr (2000 mrem/yr) is an effective dose.
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The DL for the skin is 500 mSv/yr (50 rem/yr) and it is less than the whole-body DL.
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Some organs of the body have a lower DL than the whole-body DL.
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Radiologic personnel engaged in general x-ray activity typically receive occupational radiation exposures exceeding 5 mSv/yr.
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Radiologists typically receive lower radiation exposures than radiologic technologists during fluoroscopy.
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Fixed protective barriers are always available during mobile radiography.
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Radiologic technologists are not required to wear protective aprons during mobile examinations.
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Personnel exposure during fluoroscopy is directly related to the x-ray beam-off time.
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Remote fluoroscopy results in high personnel exposures because personnel are in the x-ray examination room with the patient.
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In C-arm fluoroscopy, it is recommended to position the x-ray tube over the patient.
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Personnel engaged in interventional radiology procedures typically receive lower exposures than those in general radiologic practice.
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The recommended dose limit for radiologic personnel is 1 mSv/yr.
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Protective gloves used in interventional radiology procedures can eliminate forearm exposure.
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The goal of radiation dose reduction strategies is to keep personnel exposures as high as reasonably achievable.
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Mammography personnel exposures are high due to scatter radiation from the patient.
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Dedicated mammography x-ray units do not have personnel protective barriers.
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Personnel exposures in computed tomography (CT) facilities are high due to uncollimated x-ray beams.
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Interventional radiology procedures often involve the use of protective curtains on the image-intensifier tower.
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Radiation dose reduction strategies are not necessary in fluoroscopy procedures.
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Study Notes
CT Imaging and Radiation Exposure
- Figure 40-2 shows isoexposure profiles for horizontal and vertical planes of a multislice helical CT imaging system.
Radiation Dose Limits
- The maximum permissible dose (MPD) was specified to be the dose of radiation that would produce no significant radiation effects.
- Today, dose limits (DLs) are specified not only for whole-body exposure but also for partial-body exposure, organ exposure, and exposure of the general population.
- The whole-body DL is 50 mSv/yr (5000 mrem/yr), which takes into account the weighted average to various tissues and organs.
Occupational Radiation Dose Management
- The recommended dose limit for radiologic personnel is 50 mSv/yr (5000 mrem/yr), but experience has shown that considerably lower exposures than this are routine.
- Occupational radiation exposure of radiologic personnel engaged in general x-ray activity normally will not exceed 1 mSv/yr (100 mrem/yr).
- Radiologists usually receive slightly higher exposures than radiologic technologists due to their proximity to the radiation source during fluoroscopy.
Fluoroscopy
- Fluoroscopy and mobile radiography result in the highest occupational exposure of diagnostic x-ray personnel.
- Personnel exposure is related directly to the x-ray beam-on time, but with care, personnel exposures can be kept as low as reasonably achievable (ALARA).
- Remote fluoroscopy results in low personnel exposures because personnel are not in the x-ray examination room with the patient.
Interventional Radiology
- Personnel engaged in interventional radiology procedures often receive higher exposures than those in general radiologic practice due to longer fluoroscopic x-ray beam-on time.
- The frequent absence of a protective curtain on the image-intensifier tower and the use of cineradiography also contribute to higher personnel exposure.
- Extremity exposure during interventional radiology procedures may be significant, and protective gloves can help reduce exposure.
Mammography
- Personnel exposures associated with mammography are low because the low kVp operation results in less scatter radiation from the patient.
- Rarely does a room that is used strictly for mammography require protective lead shielding.
Computed Tomography
- Personnel exposures in computed tomography (CT) facilities are low due to the finely collimated x-ray beam and low secondary radiation levels in the examination room.
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Description
Quiz on radiology and radiation oncology physics, including CT imaging systems and radiation safety guidelines.
