EXAM #3 (Ch. 37 Patient Radiation Dose Management)

Question 1

Define ALARA

Answer 1

As Low As Reasonably Achievable.

Question 2

Define Fetal DL

Answer 2

5 mSv/9 months (500 mrem/9 months); 0.5 mSv/month (50 mrem/month) when declared.

Question 3

Define Major organogensis

Answer 3

The period of organogenesis during pregnancy is week 2 to week 10 when the organ systems of the fetus are developing.

Question 4

Define Elective booking

Answer 4

Program of elective scheduling of x-ray examinations of the abdomen and pelvis when pregnancy is unlikely.

Question 5

Define GSD

Answer 5

Genetically Significant Dose.

Question 6

Define Penumbra

Answer 6

Penumbra is an image blur that results from the size of the focal spot. A geometric tail on either side of a collimated x-ray beam.

Question 7

Define Shadow shield

Answer 7

Lead or other shielding material attached to the radiographic tube head to shield the gonads.

Question 8

Define ESD

Answer 8

ESD is acronym for Entrance Skin Dose or exposure.

Question 9

Define CT beam width

Answer 9

The size of the cone beam in multislice CT, rather than the slice thickness which is determined by detector size.

Question 10

Define MMD

Answer 10

MMD is acronym for Mean Marrow Dose.

Question 11

What is the embryo’s response to irradiation above 250 mGyt during the first 2 weeks after conception?

Answer 11

No implantation; no pregnancy.

Question 12

During the fetal period of major organogenesis, what radiation responses are possible?

Answer 12

Congenital malformations, childhood cancer and leukemia.

Question 13

What procedure should be followed if a patient is examined and subsequently discovers that she is pregnant?

Answer 13

Consult with a medical physicist who will compute the fetal radiation dose and suggest any additional necessary measures.

Question 14

List five procedures that could result in a measurable fetal dose.

Answer 14

Pelvic CT, abdominal CT, barium enema, hysterosalpingogram, low back radiography.

Question 15

How can the three cardinal principles of radiation protection best be applied in diagnostic radiology?

Answer 15

Take advantage of principles and protective devices in fluoroscopy, do not remain in the room during radiography, and maintain distance from scattering material such as the patient.

Question 16

What estimate of patient radiation dose usually is measured and reported?

Answer 16

Entrance skin exposure.

Question 17

How does one use a radiation nomogram?

Answer 17

See Figure 37-2. Draw a straight line between kVp and mAs values. It will intersect at the middle line at the correct value for ESE.

Question 18

Estimate the entrance skin dose for a PA chest image conducted at 110 kVp/2 mAs.

Answer 18

The straight line connecting 110 kVp to 2 mAs crosses the ESE line at 13 mR (130 uGya).

Question 19

What factors are required to estimate the genetically significant dose?

Answer 19

Type of examination, gonad dose per examination, age, sex, and percent of population so examined.

Question 20

What radiation dose description is most important for x-ray mammography?

Answer 20

Glandular dose.

Question 21

How do x-ray beam width and beam penumbra affect patient dose during CT?

Answer 21

In multislice spiral CT dose is slightly reduced with increasing beam width. For larger beam width the beam penumbra is less for a given imaged anatomy.

Question 22

How does the term “dose distribution” affect specification of patient radiation dose in x-ray imaging?

Answer 22

A distributed dose, as with a moving fluoroscopic beam, is more difficult to assay as a given patient dose.

Question 23

Describe how patient radiation dose during multislice CT compares with that during step-and-shoot CT.

Answer 23

Dose in multislice CT is lower than conventional step and shoot because there is less contribution from penumbra.

Question 24

Name four screening x-ray examinations that should not be performed regularly.

Answer 24

Screening x-ray examinations for tuberculosis, employment, hospital admission, and annual health exam.

Question 25

Estimate the fetal dose after an AP abdominal image is conducted at 76 kVp/40 mAs.

Answer 25

From nomogram ESE = 500 mR. The Fetal dose is (500/220) × 70 mrad = 159 mrad = (1.59 mGyt ).

Question 26

What does the symbol Σ mean?

Answer 26

The sigma symbol means summation, to add.

Question 27

Approximately what percentage of the ESD is Dg for mammography?

Answer 27

The glandular dose is approximately 15% of the ESE.

Question 28

What is the approximate contribution of CT to total patient radiation dose?

Answer 28

70%

But only 10% compared to the number of X-ray exams

Question 29

What is the approximate fetal dose after a 3.5-min barium enema fluoroscopic examination?

Answer 29

5 rad (50 mGyt).

Question 30

Patient radiation dose is expressed as what three things?

Answer 30

Patient radiation dose is expressed as entrance skin dose, gonadal dose, and bone marrow dose.

Question 31

For the average fluoroscopic examination, one can assume an ESD of __ mGyt/min.

Answer 31

For the average fluoroscopic examination, one can assume an ESD of 40 mGyt/min.

Question 32

The _____ _____ _____ (_____) is the gonad dose that, if received by every member of the population, would produce the total genetic effect on the population as the sum of the individual doses actually received.

Answer 32

The genetically significant dose (GSD) is the gonad dose that, if received by every member of the population, would produce the total genetic effect on the population as the sum of the individual doses actually received.

Question 33

_____ and _____ mammography currently are the only acceptable techniques in mammography.

Answer 33

Screen-film and digital mammography currently are the only acceptable techniques in mammography.

Question 34

Glandular dose is approximately __% of the ESE.

Answer 34

Glandular dose is approximately 15% of the ESE.

Question 35

Glandular dose should not exceed __ mGyt/view with contact mammography and __ mGyt/view with a grid.

Answer 35

Glandular dose should not exceed 1 mGyt/view with contact mammography and 3 mGyt/view with a grid.

Question 36

JUST REMEMBER: It is essential that CT collimators be monitored periodically for proper adjustment.

Answer 36

JUST REMEMBER: It is essential that CT collimators be monitored periodically for proper adjustment.

Question 37

The higher the multislice value, the HIGHER/LOWER the patient dose will be.

Answer 37

The higher the multislice value, the LOWER the patient dose will be.

Question 38

A reduction in the noise or beam width, while other factors remain constant, INCREASES/DECREASES patient dose.

Answer 38

A reduction in the noise or beam width, while other factors remain constant, INCREASES patient dose.

Question 39

JUST REMEMBER: It should never be necessary to repeat a digital radiographic examination.

Answer 39

JUST REMEMBER: It should never be necessary to repeat a digital radiographic examination.

Question 40

Digital radiography can be conducted at higher kVp, resulting in HIGHER/LOWER patient dose.

Answer 40

Digital radiography can be conducted at higher kVp, resulting in LOWER patient dose.

Question 41

The FASTEST/SLOWEST-speed screen-film combination consistent with the nature of the examination should be used.

Answer 41

The FASTEST-speed screen-film combination consistent with the nature of the examination should be used.

Question 42

How do we meet our responsibility to inform pregnant patients?

Answer 42

We meet our responsibility to the pregnant patient by posting signs in the waiting room.