X-ray Interactions, Attenuation, Differential Absorption, Contrast Agents

Question 1

Coherent scattering is best described as:
a) Complete absorption of the x-ray
b) Ionization with energy loss
c) Change in direction with no loss of energy
d) Nuclear interaction

Answer 1

c) Change in direction with no loss of energy — Coherent scatter alters direction only and has little diagnostic importance.

Question 2

Which x-ray interaction is of little importance in diagnostic radiology?
a) Photoelectric effect
b) Compton scattering
c) Coherent scattering
d) Differential absorption

Answer 2

c) Coherent scattering — It contributes minimally to image formation.

Question 3

The probability of Compton scattering is:
a) Directly proportional to atomic number
b) Inversely proportional to atomic number
c) Independent of atomic number and inversely proportional to energy
d) Directly proportional to energy

Answer 3

c) Independent of atomic number and inversely proportional to energy — Compton scatter depends mainly on electron density.

Question 4

Compton scattering primarily affects the image by:
a) Increasing contrast
b) Eliminating noise
c) Reducing image contrast
d) Increasing sharpness

Answer 4

c) Reducing image contrast — Scatter adds unwanted exposure to the image receptor.

Question 5

The photoelectric effect is:
a) Partial absorption with scatter
b) Total absorption of the x-ray
c) Change in direction without energy loss
d) Nuclear interaction

Answer 5

b) Total absorption of the x-ray — All photon energy is absorbed.

Question 6

The probability of the photoelectric effect is proportional to:
a) 1/E
b) 1/E²
c) 1/E³ and Z³
d) Z only

Answer 6

c) 1/E³ and Z³ — Strongly dependent on low energy and high atomic number.

Question 7

Pair production occurs in diagnostic x-ray imaging:
a) Frequently
b) Occasionally
c) Only at low kVp
d) Never

Answer 7

d) Never — Pair production requires energies above diagnostic range.

Question 8

Differential absorption occurs because of:
a) Only photoelectric effect
b) Only Compton scattering
c) Scatter only
d) Photoelectric absorption, Compton scatter, and transmitted x-rays

Answer 8

d) Photoelectric absorption, Compton scatter, and transmitted x-rays — All contribute to image formation.

Question 9

Differential absorption increases when:
a) kVp is increased
b) kVp is decreased
c) SID is increased
d) Filtration is increased

Answer 9

b) kVp is decreased — Lower kVp increases contrast differences.

Question 10

To visualize small differences in soft tissue, the technologist should use:
a) High kVp
b) Long SID
c) Low kVp
d) Heavy filtration

Answer 10

c) Low kVp — Maximizes differential absorption.

Question 11

The interaction of x-rays with tissue is proportional to:
a) Atomic number only
b) Photon energy only
c) Mass density regardless of interaction type
d) Thickness only

Answer 11

c) Mass density regardless of interaction type — Denser tissues interact more.

Question 12

Attenuation is defined as:
a) Scatter only
b) Absorption only
c) Transmission only
d) Absorption plus scattering

Answer 12

d) Absorption plus scattering — Both processes reduce beam intensity.

Question 13

Which interactions are most important in diagnostic imaging?
a) Coherent and pair production
b) Photoelectric and Compton
c) Photodisintegration and pair production
d) Coherent and photoelectric

Answer 13

b) Photoelectric and Compton — These dominate diagnostic interactions.

Question 14

Differential absorption primarily controls:
a) Spatial resolution
b) Image contrast
c) Image noise
d) Magnification

Answer 14

b) Image contrast — Contrast depends on absorption differences.

Question 15

The x-ray image results from:
a) All x-rays absorbed
b) Only scattered x-rays
c) Differences between absorbed and transmitted x-rays
d) Only Compton interactions

Answer 15

c) Differences between absorbed and transmitted x-rays — Image-forming x-rays create contrast.

Question 16

Attenuation of an x-ray beam depends on:
a) Tissue atomic number
b) Tissue mass density
c) X-ray energy
d) All of the above

Answer 16

d) All of the above — All three influence attenuation.

Question 17

Radiologic contrast agents work by:
a) Increasing scatter
b) Reducing beam energy
c) Increasing differential absorption
d) Reducing patient dose

Answer 17

c) Increasing differential absorption — High-Z materials enhance contrast.

Question 18

Iodine is commonly used for imaging:
a) GI tract only
b) Bone
c) Vascular, renal, and biliary systems
d) Lung tissue

Answer 18

c) Vascular, renal, and biliary systems — Iodine highlights soft tissues.

Question 19

Barium is primarily used for:
a) Vascular imaging
b) Renal imaging
c) Gastrointestinal imaging
d) Pulmonary imaging

Answer 19

c) Gastrointestinal imaging — Barium coats the GI tract.

Question 20

Why are iodine and barium effective contrast agents?
a) Low density
b) Low atomic number
c) High atomic number and mass density
d) High filtration

Answer 20

c) High atomic number and mass density — These increase photoelectric absorption.