Dose Limits

Question 1

ICRP Occupational Annual EFFECTIVE Dose Limit (Stochastic)

Answer 1

20 mSv/yr, averaged over 5 years, with no more than 50 mSv in any one year

Question 2

ICRP Occupational Annual EQUIVALENT Dose Limit (Non-Stochastic)

Answer 2

500 mSv/yr (to skin, hands, and feet), except lens of the eye, 150 mSv/yr

Question 3

ICRP Public Annual EFFECTIVE Dose Limit (Stochastic)

Answer 3

1 mSv/yr (a higher value of effective dose could be allowed in a year provided that the average over 5 years does not exceed 1 mSv in a year)

Question 4

ICRP Public Annual EQUIVALENT Dose Limit (Non-Stochastic)

Answer 4

50 mSv/yr (to skin), except lens of the eye, 15 mSv/yr

Question 5

ICRP Control on EFFECTIVE Dose of 20-100 mSv, annual or acute

Answer 5

Consider reducing dose. Controlled by action on exposure pathway (eg. Walls, lead, etc.), radiological emergency reference level.

Question 6

ICRP Control on EFFECTIVE Dose of 1-20 mSv, annual or acute

Answer 6

For planned exposure situations, individual dose assessment and training (eg. PPE). Controlled by action on source or exposure pathway (eg. Blocks, walls, lead, etc.).

Question 7

ICRP Control on EFFECTIVE Dose of <1 mSv, annual or acute

Answer 7

Periodic checks on exposure pathway. Constraints for public exposure in planned situations.

Question 8

NCRP Occupational Annual EFFECTIVE Dose Limit (Stochastic)

Answer 8

50 mSv/yr (excluding doses from natural sources)

Question 9

NCRP Occupational Cumulative EFFECTIVE Dose Limit (Stochastic)

Answer 9

10 x Age mSv (excluding doses from natural sources)

Question 10

Occupational Annual EQUIVALENT Dose Limits (Non-Stochastic)

Answer 10

500 mSv/yr to all organs except lens of the eye, 150 mSv/yr (excluding doses from natural sources)

Question 11

NCRP Public Annual EFFECTIVE Dose Limit, if Frequent (Stochastic)

Answer 11

1 mSv/yr (excluding doses from natural sources)

Question 12

Public Annual EFFECTIVE Dose Limit, if Infrequent (Stochastic)

Answer 12

5 mSv/yr (excluding doses from natural sources)

Question 13

NCRP Public Annual EQUIVALENT Dose Limit (Non-Stochastic)

Answer 13

50 mSv/yr to all organs except lens of the eye, 15 mSv/yr (excluding doses from natural sources)

Question 14

Embryo / Fetus Monthly EQUIVALENT Dose Limit (there are no EFFECTIVE Dose Limits)

Answer 14

0.5 mSv/month

Question 15

NCRP Negligible Annual EQUIVALENT/EFFECTIVE Dose

Answer 15

0.01 mSv/yr (excluding doses from natural sources)

Question 16

Mobile radiographic equipment requirements

Answer 16

Exposure cord must permit the operator to stand at least 6 ft, exposure switches NEED NOT be the two-stage type, a lead apron should be carried with the unit and worn, the radiographer must alert individuals in the area before making the exposure

Question 17

Guidelines for the use of protective shielding for gonadal shielding

Answer 17

If the patient has reasonable reproductive potential, when the gonads are within 5 cm of the collimated field

Question 18

Approximate entrance skin esposure (ESE) for the average anteroposterior (AP) supine abdomen radiograph

Answer 18

300 mrad (or ~3 mSv)

Question 19

Grid vs. Collimator

Answer 19

Grids are used POST-PATIENT EXPOSURE to reduce blur in images, collimators are used PRE-PATIENT EXPOSURE, thus collimators can reduce dose while grids cannot.

Question 20

Assumptions about patient x-ray scatter intensity at 1 m?

Answer 20

Intensity is 1/1000th the intensity right before scattering.

Question 21

NCRP Minimum Lead Apron Thickness Minimum Requirement

Answer 21

0.5 mm Pb

Question 22

NCRP Leakage Radiation Limit at 1 m

Answer 22

100 mR / hr

Question 23

Radiation safety in fluoroscopy

Answer 23

1. Tabletop radiation intensity must not exceed 2.1 R / min / mA
2. Tabletop radiation intensity must not exceed 10 R / min
3. In high-level fluoroscopy, tabletop intensity up to 20 R / min is permitted

Question 24

Primary Radiation Lead Shielding Minimum Requirement

Answer 24

1/16 inch Pb

Question 25

Use Factor

Answer 25

Fraction of time a particular wall is being irradiated by a PRIMARY beam during scans.