2022 - 32 Radiation Safety

Question 1

What are the effects of adjustments to an X-ray table, such as decreasing milliamperes, exposure time, distance from the emitter, and kVp, on radiation exposure?

Answer 1

Decreasing milliamperes and exposure time reduces radiation exposure linearly. Increasing the distance from the emitter reduces exposure by the inverse square law. Decreasing kVp reduces exposure but also affects image quality.

Question 2

What is the maximum yearly occupational exposure to radiation recommended by the International Commission on Radiological Protection (ICRP)?

Answer 2

The ICRP recommends a maximum yearly occupational exposure limit of 50mSV or 20 per year over 5 years.

Question 3

Which urological procedures expose the physician to different levels of radiation, and which one exposes the physician to the most radiation?

Answer 3

Thresholds and stone sizes vary by guidelines, and details specific to the document must be referred to for the precise answer.

Question 4

What does ALARA stand for in the context of radiation safety?

Answer 4

ALARA stands for “As Low As Reasonably Achievable,” emphasizing minimizing radiation exposure.

Question 5

Why is understanding the principles of ionizing radiation important for urologists?

Answer 5

Understanding ionizing radiation’s principles is essential for urologists to enhance diagnosis and treatment, ensure patient and provider safety, and comply with regulations and guidelines.

Question 6

How is the construction of X-ray tubes designed to prevent stray radiation?

Answer 6

X-ray tubes are housed in steel or tungsten casing with a narrow beryllium window, allowing only focused X-rays to pass and eliminating low-energy photons.

Question 7

What factors influence the quality of an X-ray image?

Answer 7

The image quality depends on the energy and quantity of electrons reaching the detector, determined by potential voltage difference (kVp), current (mA), and exposure time (s).

Question 8

What is the role of adjustable lead collimators in X-ray imaging?

Answer 8

Adjustable lead collimators limit the area of radiation exposure by focusing the beam on the region of interest, helping target specific areas without unnecessary exposure.

Question 9

What are the three principles of ALARA, and how are they used in radiation safety?

Answer 9

The three principles of ALARA are time, distance, and shielding, used to reduce radiation exposure by minimizing exposure time, maximizing distance from the radiation source, and using appropriate shielding.

Question 10

How is radiation exposure tracked, and what is the most common type of dosimeter?

Answer 10

Radiation exposure is tracked using dosimeters, with the thermoluminescent dosimeter being the most common. It measures whole body radiation.

Question 11

What are the recommended radiation exposure limits for pregnant urologists or trainees, according to the Nuclear Regulatory Commission?

Answer 11

The recommended exposure limit for an embryo/fetus is 500 mrem or 5 mSv or less during pregnancy.

Question 12

What is the linear no-threshold model, and how does it approach radiation exposure?

Answer 12

The linear no-threshold model suggests that radiation exposure is additive over time and can be linearly extrapolated to determine risk. It posits that there’s no safe threshold, and every exposure adds to the risk.

Question 13

What is the recommended occupational exposure limit by the International Commission on Radiological Protection (ICRP)?

Answer 13

The ICRP recommends limiting occupational exposure to 50 mSv per year or no more than 20 mSv yearly over a 5-year period.

Question 14

How does the hormesis theory view low doses of radiation?

Answer 14

The hormesis theory suggests that radiation at low doses may serve a protective role, and below certain thresholds, ionizing radiation will not contribute to an increased risk of malignancy.

Question 15

What is the radiation exposure range for the fetus during KUB radiography in pregnancy?

Answer 15

During KUB radiography in pregnancy, the fetus is exposed to 0.2 to 0.25 mSv of radiation.

Question 16

What are the benefits and risks of performing URS during pregnancy?

Answer 16

URS can be safely performed during pregnancy to manage obstructing ureteral stones and offers the benefit of definitive stone removal. However, there may be a risk of premature delivery associated with postoperative urinary tract infection.

Question 17

What precautions should be taken when performing URS on a pregnant female to reduce radiation exposure to the fetus?

Answer 17

Shielding should be placed under the pelvis in the presumed area of fetal lay and the contralateral kidney. Shielding on top of the patient should be avoided as it would increase radiation exposure due to X-ray reflection.

Question 18

What considerations should be made for pediatric patients regarding radiation exposure?

Answer 18

Efforts should be made to pursue non-radiation modalities first. If MRI is obtained, the risk of anesthesia should be weighed against the benefits of avoiding radiation. CT settings should be adjusted according to the child’s size.

Question 19

What mSV of exposure is the threshold of a low-dose CT scan, and at what size stone do sensitivity and specificity begin to decrease using low-dose scans?

Answer 19

The threshold of a low-dose CT scan is <3 mSv of exposure, and sensitivity and specificity begin to decrease for kidney stone measurements >2 mm.

Question 20

What are adjustable lead collimators, and how do they function?

Answer 20

Adjustable lead collimators limit the area of radiation exposure by focusing the X-ray beam on the specific region of interest.

Question 21

Which adjustment to an x-ray table would reduce exposure by the greatest amount?

Answer 21

Decreasing the kVp by a factor of 2, as reducing kVp has an exponentially greater impact on reducing radiation dosage.

Question 22

What is the exposure formula for x-rays, and what variables contribute to exposure?

Answer 22

Exposure∝mA×s×kVp
5
×
Distance
2

1
​

Question 23

How are x-ray tubes constructed, and what are their functions?

Answer 23

X-ray tubes are housed in steel or tungsten casing with a narrow beryllium window, eliminating low-energy photons and focusing the x-ray beam. They prevent stray radiation and help focus the beam.
Flashcard 3

Question 24

What is exposure proportional to?

Answer 24

An increase in
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kVp will have a much greater effect on exposure than increasing
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×
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mA×s.

Question 25

What is the equivalent of 1 Gy (gray) in rad (radiation absorbed dose)?

Answer 25

1 Gy is equivalent to 100 rad.

Question 26

How many rad are equivalent to 0.01 Gy?

Answer 26

0.01 Gy is equivalent to 1 rad.

Question 27

What is the equivalent of 1 Sv (sievert) in rem (roentgen equivalent man)?

Answer 27

1 Sv is equivalent to 100 rem.

Question 28

How many rem are equivalent to 0.1 Sv?

Answer 28

0.1 Sv is equivalent to 1 rem.