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Questions and Answers
According to the NCRP, the whole-body DL is _______ mSv/yr.
50
In smaller hospitals, occupational exposures rarely exceed _______ mSv/yr.
5
Radiologic personnel should never exceed _______ mSv/yr.
50
The maximum permissible dose was specified to produce no _______ radiation effects.
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The dose limits include not only whole-body exposure but also _______ exposure and organ exposure.
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The dose limit for the skin is _______ mSv/yr.
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The MPD was the dose of radiation that would be expected to produce no _______ radiation effects.
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Average exposures in most facilities are less than _______ mSv/yr.
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The recommended dose limit for radiologic personnel is __________ mSv/yr
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Radiologic personnel engaged in general x-ray activity normally will not exceed __________ mSv/yr
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Radiologists usually receive slightly higher exposures than __________
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The radiologist receives most of his or her exposure during __________ and is usually closer to the radiation source
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The highest occupational exposure of diagnostic x-ray personnel occurs during __________ and mobile radiography
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When fixed protective barriers are not available, such as during __________ examination, the mobile x-ray imaging system is equipped with an exposure cord
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The radiologic technologist should wear a __________ apron for each such mobile examination
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Personnel exposure is related directly to the x-ray __________ time
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The frequent absence of a protective __________ on the image-intensifier tower contributes to higher personnel exposure.
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Even with protective gloves, exposure of the __________ can approach the recommended dose limit of 500 mSv/yr.
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Dedicated mammography x-ray units have personnel protective barriers made of __________ glass.
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Radiation levels are low in CT facilities compared with those experienced in __________.
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Personnel engaged in interventional radiology procedures often receive higher exposures than do those in general __________ practice.
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The recommended dose limit for extremity exposure is __________ mSv/yr.
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During C-arm fluoroscopy, it is best to position the x-ray tube __________ the patient.
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Without protective gloves, excessive __________ exposures are possible.
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Study Notes
Radiation Oncology Physics
- Figure 40-2 shows the isoexposure profiles for the horizontal and vertical planes of a multislice helical CT imaging system.
C-Arm Fluoroscopy
- During C-arm fluoroscopy, the x-ray beam may be on for a relatively long time and can be pointed in virtually any direction.
Radiation Dose Limits
- Radiation personnel should never exceed 50 mSv/yr (5000 mrem/yr).
- In smaller hospitals, emergency centers, and private clinics, occupational exposures rarely exceed 5 mSv/yr (500 mrem/yr).
- Average exposures in most facilities are less than 1 mSv/yr (100 mrem/yr).
Whole-Body Dose Limits
- Today, dose limits (DLs) are specified for whole-body exposure, partial-body exposure, organ exposure, and exposure of the general population, excluding medical exposure as a patient and exposure from natural sources.
- The whole-body DL is 50 mSv/yr (5000 mrem/yr), which is an effective dose that takes into account the weighted average to various tissues and organs.
Dose Limits for Tissues and Organs
- Specific tissues and organs have specific recommended dose limits.
- The DL for the skin is 500 mSv/yr (50 rem/yr).
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).
Fluoroscopy
- Unquestionably, the highest occupational exposure of diagnostic x-ray personnel occurs during fluoroscopy and mobile radiography.
- Personnel exposure is related directly to the x-ray beam-on time.
- With care, personnel exposures can be kept as low as reasonably achievable (ALARA).
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.
Mammography
- Personnel exposures associated with mammography are low because the low kVp of the 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.
- Because the CT x-ray beam is finely collimated and only secondary radiation is present in the examination room, radiation levels are low compared with those experienced in fluoroscopy.
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Description
This quiz covers radiation oncology physics, including CT imaging systems, C-arm fluoroscopy, and radiation safety guidelines.
