Radiation Oncology Physics Quiz
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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.

<p>significant</p> Signup and view all the answers

The dose limits include not only whole-body exposure but also _______ exposure and organ exposure.

<p>partial-body</p> Signup and view all the answers

The dose limit for the skin is _______ mSv/yr.

<p>500</p> Signup and view all the answers

The MPD was the dose of radiation that would be expected to produce no _______ radiation effects.

<p>significant</p> Signup and view all the answers

Average exposures in most facilities are less than _______ mSv/yr.

<p>1</p> Signup and view all the answers

The recommended dose limit for radiologic personnel is __________ mSv/yr

<p>50</p> Signup and view all the answers

Radiologic personnel engaged in general x-ray activity normally will not exceed __________ mSv/yr

<p>1</p> Signup and view all the answers

Radiologists usually receive slightly higher exposures than __________

<p>radiologic technologists</p> Signup and view all the answers

The radiologist receives most of his or her exposure during __________ and is usually closer to the radiation source

<p>fluoroscopy</p> Signup and view all the answers

The highest occupational exposure of diagnostic x-ray personnel occurs during __________ and mobile radiography

<p>fluoroscopy</p> Signup and view all the answers

When fixed protective barriers are not available, such as during __________ examination, the mobile x-ray imaging system is equipped with an exposure cord

<p>mobile</p> Signup and view all the answers

The radiologic technologist should wear a __________ apron for each such mobile examination

<p>protective</p> Signup and view all the answers

Personnel exposure is related directly to the x-ray __________ time

<p>beam-on</p> Signup and view all the answers

The frequent absence of a protective __________ on the image-intensifier tower contributes to higher personnel exposure.

<p>curtain</p> Signup and view all the answers

Even with protective gloves, exposure of the __________ can approach the recommended dose limit of 500 mSv/yr.

<p>forearm</p> Signup and view all the answers

Dedicated mammography x-ray units have personnel protective barriers made of __________ glass.

<p>lead</p> Signup and view all the answers

Radiation levels are low in CT facilities compared with those experienced in __________.

<p>fluoroscopy</p> Signup and view all the answers

Personnel engaged in interventional radiology procedures often receive higher exposures than do those in general __________ practice.

<p>radiologic</p> Signup and view all the answers

The recommended dose limit for extremity exposure is __________ mSv/yr.

<p>500</p> Signup and view all the answers

During C-arm fluoroscopy, it is best to position the x-ray tube __________ the patient.

<p>under</p> Signup and view all the answers

Without protective gloves, excessive __________ exposures are possible.

<p>hand</p> Signup and view all the answers

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.

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