Chapter 13

With higher radiation exposure to the patient during a computed tomography examination, there is

a.

a decreased associated cancer risk because the radiation is more penetrating.

b.

an increased associated cancer risk.

c.

a negligible associated cancer risk because the radiation is less penetrating.

d.

an extremely large cancer risk.

B

Which of the following is not typically used during a CT scan?

1. A tightly collimated x-ray beam

2. Direct patient shielding

3. Filtered back projection

a.

1 only

b.

2 only

c.

3 only

d.

1, 2, and 3

B

In CT because of higher effective energy of the x-ray beam, both ____________ and _______________ interactions contribute substantially to the image.

a.

coherent; photodisintegration

b.

classical; pair production

c.

photoelectric; Compton

d.

Compton; photodisintegration

C

Which of the following are relevant dose parameters in CT?

1. CT dose index (CTDI)

2. CTDIw

3. CTDIVOL

4. Dose length product (DLP)

a.

1, 2, and 3 only

b.

2, 3, and 4 only

c.

1, 3, and 4 only

d.

1, 2, 3, and 4

D

DLP represents the product of the CTDIVOL and the irradiated scan length. In what unit of measure is it usually expressed?

a.

mGy-cm

b.

mSv-cm

c.

mGy-mSv

d.

mSv-mRa

A

Which of the following terms are synonymous?

1. Automatic exposure control

2. Iterative reconstruction

3. Tube current modulation

a.

1 and 2 only

b.

1 and 3 only

c.

2 and 3 only

d.

1, 2, and 3

B

A miscentering of ________ can produce as much as __________% increase in patient dose.

a.

2 cm; 50

b.

2 cm; 25

c.

1 cm; 75

d.

1 cm; 60

B

Which of the following terms are synonymous in relation to computed tomography?

1. Diagonal

2. Helical

3. Spiral

a.

1 and 2 only

b.

1 and 3 only

c.

2 and 3 only

d.

1, 2, and 3

C

For routine head and body computed tomography examinations, effective doses fall into which of the following effective dose ranges?

a.

1 to 10 mSv

b.

20 to 30 mSv

c.

40 to 50 mSv

d.

60 to 70 mSv

A

For mammography molybdenum filters allow a (an) _________________ than rhodium filters.

a.

higher energy window

b.

lower energy window

c.

equal energy window

d.

comparable energy window

B

The entrance exposure from a CT examination may be compared with the entrance exposure received during which of the following procedures?

a.

Screening mammography

b.

A routine radiographic series of the lumbar spine with five projections

c.

A routine radiographic series of the paranasal sinuses with four projections

d.

A routine fluoroscopic examination

D

Tube current modulation in CT scanning can

a.

increase patient dose significantly.

b.

increase patient dose only slightly.

c.

help to reduce patient dose.

d.

not affect patient dose.

C

Verifying that the center of the patient coincides with the center of the CT gantry is a significant part of dose reduction strategies that is under the control of the

a.

CT technologist.

b.

hospital or imaging facility administrator.

c.

ordering physician.

d.

patient.

A

Filtering refers to changing the projection data before doing the back projections to remove the

a.

blurriness.

b.

contrast.

c.

grayness.

d.

scattered radiation.

A

In mammography maintaining and enhancing subject contrast is

a.

not important.

b.

minimally important.

c.

of paramount importance for all patients.

d.

only important for patients with dense breasts.

C

Digital mammography units with the ability to enhance contrast with image gray-level manipulation offer

a.

substantial improvement for patients with small breasts.

b.

substantial improvement for patients with microcalcifications in small breasts.

c.

substantial improvement for patients with dense breasts.

d.

poor quality images for patients with dense breasts and microcalcifications.

C

During mammography, axillary projections should be done only on request of the

a.

ordering physician.

b.

patient.

c.

radiologist.

d.

technologist performing the examination.

C

In CT when a series of adjacent slices is obtained, some radiation will also scatter from the slice being made into the adjacent slices. What is this radiation called?

a.

Forward scatter

b.

Backscatter

c.

Interslice scatter

d.

Side scatter

C

In spiral image acquisition, the patient table moves during the acquisition so that a

a.

single-dimension image is obtained.

b.

three-dimensional data set is obtained.

c.

four-dimensional data set is obtained.

d.

six-dimensional data set is obtained.

B

Lower tube current is used in anatomic regions where there is ____________ attenuation because the anatomy is ____________ or _________ dense.

a.

increased; thicker; more

b.

decreased; thicker; more

c.

increased; thinner; less

d.

decreased; thinner; less

D

In the early 2000s various publications calculated individual and population risks of cancer from CT based upon risk estimates from studies of which of the following groups of people?

a.

Atomic bomb survivors

b.

Early radiologists and radiographers

c.

Patients undergoing treatment for thyroid cancer

d.

The general public who were exposed to natural background radiation

A

In computed tomography the dose at the edge of a beam does not decrease to _________ immediately.

a.

15 cGy

b.

10 cGy

c.

5 cGy

d.

0 (zero)

D

______________ is the relationship between the movement or advancement of the patient couch and the x-ray beam collimator dimension.

a.

Dose distribution

b.

Iterative reconstruction

c.

Pitch

d.

Tube current modulation

C

The movement or advancement of the patient couch is known as

a.

optimization.

b.

iterative reconstruction.

c.

tube current modulation.

d.

table increment.

D

Which of the following groups advocate annual mammography screening or mammography screening at least every other year?

1. American College of Radiology

2. American Cancer Society

3. American Medical Association

a.

1 and 2 only

b.

1 and 3 only

c.

2 and 3 only

d.

1, 2, and 3

D