Mosby's Comprehensive Review of Radiography: Challenge Test 1

Attenuation:

describes changes in the x-ray beam as it travels through the patient

Which photon-tissue interaction makes radiography

possible because of its creation of contrast?

photoelectric

Which photon-tissue interaction produces radiation that may expose others in the room during fluoroscopy?

compton

The unit of radiation absorbed in air is the:

gray(a)

The unit of radioactivity is the:

becquerel

The unit of effective dose is the:

sievert

Linear energy transfer:

varies for different types of radiation

The unit of Bq would be used in what imaging modality?

nuclear medicine

Medical x-rays are an example of:

nonionizing radiation

Graphs that show the relationship between radiation received and the organism's responses are called:

exposure curves

Cataractogenesis does not occur at low levels of radiation exposure; it is best expressed by which of the following dose-response relationships?

threshold

"Increased dose equals increased probability of effects" best describes which of the following?

stochastic effects

The cumulative occupational exposure for a 22-year-old radiographer is:

220 mSv

The annual effective dose limit for the general public, assuming frequent exposure, is:

1.0 mSv

The secondary protective barrier used in room shielding must be at least how thick?

{1⁄32}-inch Pb equivalent

If the air kerma measured 6 feet from the x-ray table is 5 Graya, what is the air kerma measured at a distance of 3 feet?

1.25 Gray(a)

The intensity of the scattered beam is 1⁄1000 the intensity of the primary beam at a ________ angle 1 m from the patient.

45-degree

The minimum source-to-skin distance for fixed fluoro scopes is:

15 inches

When increased dose equals increased severity of tissue reactions, this is called:

deterministic

"Cells that are oxygenated are more susceptible to radiation damage"; this describes:

oxygen enhancement ratio

The blood count is depressed after a whole-body dose equivalent of at least how many mSv?

0.25 mSv

Highly reactive ions that have unpaired electrons in the outer shell are called:

free radicals

The master molecule that directs cell activities is:

DNA

The process of somatic cell division is called:

mitosis

The most common effect from exposure to ionizing radiation is:

a. Mutations

b. Ionization of atoms in the cells

c. Cell death

d. Nothing

Although all of these effects may occur, the most common result of LET is no effect. Nevertheless, ALARA must still be practiced.

Most radiation-induced damage to cells occurs:

at doses of radiation much higher than doses used in radiography

Radiation doses up to ________ are considered relatively low risk to the embryo and fetus.

5 mSv

A concept of radiologic practice that encourages radiation users to adopt measures that keep the dose to the patient and themselves at minimum levels is called:

ALARA

Which of the following is (are) relatively insensitive to radiation?

nerve tissue

Somatic effects of radiation:

are cause when a large dose of high-LET radiation is received by a large area of the body

The best way to keep the radiation dose to the patient low is:

avoidance of repeat exposures

X-rays may remove electrons from atoms in the body by a process called:

ionization

Ionization may cause:

unstable atoms

Cell damage may be exhibited as:

loss of function or abnormal function

Damage to the cell being irradiated is called:

somatic

Radiation effects that show up in the next generation are called:

genetic

Radiation that is contained in the environment is called:

natural background

Background radiation is the source of approximately what percent of human exposure?

50%

The annual effective dose per person from natural background radiation is approximately:

3.0 mSv

The greatest source of natural background radiation to humans is:

Radon

According to NCRP Report #160, the increase in total exposure is primarily attributed to increased use of:

CT

What barrier must be at least 1⁄16-inch lead equivalent?

primary protective barrier

CT accounts for approximately what percent dose to the population (NCRP Report #160)?

24%

Meiosis describes the process of division of what type of cells?

germ

What refers to the lifetime-accumulated occupational dose?

cumulative effective dose

Exposure times longer than ______ minutes can lead to skin effects.

30

What provides an approximate skin dose where the x-ray beam is entering the patient?

air kerma

The preferred term for radiation exposure is:

sievert

Effective dose limits may be found in what published material?

NCRP reports

Photon-cell interactions occur:

by chance

The smallest particle of an element that retains the characteristics of the element is a(n):

atom

Atomic mass refers to

the number of protons plus the number of neutrons

X-rays travel as bundles of energy called:

photons

The height of a sine wave is called the:

amplitude

The transformer that operates on the principle of self-induction is the:

autotransformer

Electronic timers used in x-ray equipment allow for

exposure times as short as:

1⁄1000 second

To ensure consistency of radiographic quality from one exposure to the next, what device may be used?

automatic exposure control

An x-ray machine that uses a continually decreasing mA for the shortest times possible uses a(n):

falling load generator

Devices in the x-ray circuit that operate on the principle of mutual induction are called:

transformers

The high-voltage section of the x-ray circuit makes use of what type of transformer

step-up

The device in the x-ray circuit that changes AC to DC is the:

rectifier

What type of current is required for proper operation of the x-ray tube?

direct

The result of thermionic emission is a(n):

electron cloud

The focusing cup is located at the:

cathode

An interaction that produces x-rays at the anode as a result of outer shell electrons filling holes in the K-shell is called:

characteristic

In digital fluoroscopy, the image should be viewed on what device to take advantage of the digital capabilities?

high-resolution monitor

A primary advantage of digital fluoroscopy is:

postprocessing manipulation of the image

In digital fluoroscopy and computed radiography, the energy must be changed to a digital form by a(n):

analog-to-digital converter

An algorithm is:

a mathematical formula used to reconstruct the image in digital imaging

In computed radiography, each pixel corresponds to a shade of gray representing an area in the patient known as a(n):

voxel

Lightness and darkness of the image in computed radiography may be adjusted by:

adjusting the window level

The window level in computed radiography is the:

midpoint of densities

Radiographic contrast in computed radiography may be adjusted by changing the:

window width

The amount of receptor exposure is controlled primarily by:

mAs

The visible image may also be called the:

manifest image

The quantity of x-rays produced is directly controlled by:

mAs

The rule or law that governs changing technique using kVp is the:

15% rule

If SID is halved, what may be said about receptor exposure?

receptor exposure is quadrupled

Distortion that affects the size of the object as represented on the radiographic image is called:

magnification

Shape distortion may take the form of:

elongation and foreshortening

A longer than usual OID may cause:

magnification

CR cassettes should be erased at least:

every 24 hours

The equation H/D describes:

grid ratio

If the exposure field is not accurately recognized, the histogram:

widens

Noise increases with an increase in

speed class

Edge enhancement provides:

artificial increase in display contrast at an edge of the image

Which of the following grid errors would result in an image that shows normal exposure in the middle but decreased exposure on the sides and may follow removal and replacement of the grid?

upside down

Grid frequency is described as the:

number of lead strips per inch or centimeter

When working with CR and DR, one must be aware that their response to scatter radiation is:

very sensitive

The images on radiologists' monitors appear:

in greater detail than on radiographers’ monitors

A histogram analysis error may be caused by:

inappropriate collimation

Smoothing provides:

evenness in brightness

Consistency of image appearance is achieved through the use of:

uniform processing codes

Which of the following sets of exposure factors would produce an image with the poorest spatial resolution?

a. 60 mAs, 80 kVp, 40-inch SID, 4-inch OID

b. 30 mAs, 92 kVp, 40-inch SID, 4-inch OID

c. 120 mAs, 92 kVp, 20-inch SID, 4-inch OID

d. 15 mAs, 100 kVp, 40-inch SID, 4-inch OID

C

Which of the following sets of exposure factors would produce an image with the best spatial resolution?

a. 60 mAs, 80 kVp, 72-inch SID, 4-inch OID

b. 30 mAs, 92 kVp, 40-inch SID, 4-inch OID

c. 120 mAs, 92 kVp, 20-inch SID, 4-inch OID

d. 15 mAs, 100 kVp, 40-inch SID, 4-inch OID

A

Beam restriction has the following effect on contrast:

shorter scale of contrast

As kVp increases, there is an increased production of:

short wavelengths

The relationship between kVp and receptor exposures:

direct, although not proportional

Grids that have strips angled to coincide with divergence of the x-ray beam are called:

focused

In digital imaging, the radiographer must be aware that:

the image is determined by the total exposure