Chapter 14 Review Questions

Question 1

Afterloading techniques were developed primarily to reduce:

Answer 1

exposure to personnel

Question 2

Which of the following statements about radioactivity is true?

a. The change in the number of atoms per unit time is proportional to the number of atoms present.
b. The change in unit time per change in the number of atoms is proportional to the number of atoms present.
c. The change in the number of atoms per unit time is equal to the number of disintegrations per second.
d. The change per unit time per change in the number of atoms is proportional to the number of disintegrations per second.

Answer 2

A

Question 3

The decay constant describes:

a. the half-life of a particular radionuclide.
b. the number of ionizations produced in tissue per unit time.
c. the fraction of the number of atoms that decay per unit time.
d. none of the above.

Answer 3

the fraction of the number of atoms that decay per unit time

Question 4

the average lifetime of radioactive atoms is the definition of:

a. half-life.
b. decay constant.
c. specific activity.
d. mean life.

Answer 4

mean life

Question 5

The dose profile (depth dose curve) around a brachytherapy source depends on the source’s:

a. activity.
b. strength.
c. energy.
d. half-life

Answer 5

energy

Question 6

The most commonly used isotopes for permanent implants are:

a. I-125 and Pd-103
b. Au-198 and I-125
c. Cs-137 and Pd-103
d. Ra-226 and Ir-192

Answer 6

I-125 and Pd-103

Question 7

Packing in gynecologic implants serves which of the following purposes?
I. Spaces sources to even out dose distributions.
II. Aids in pushing dose-sensitive structures farther from the sources
III. Provides stability of applicator placement.

Answer 7

II and III

Question 8

A source’s activity is:

a. inversely proportional to the particle energy.
b. inversely proportional to treatment time.
c. inversely proportional to dose rate.
d. inversely proportional to exposure rate.

Answer 8

inversely proportional to treatment time.

Question 9

when is interstitial brachytherapy used

Answer 9

prostate and breast

Question 10

when is intracavitary brachytherapy used

Answer 10

cervical cancer

Question 11

when is intraluminal brachtherapy used

Answer 11

esophagus and bronchus cancer

Question 12

when is surface brachytherapy used

Answer 12

ocular tumors

Question 13

Time period in which the activity decays to one half of the original value.

Answer 13

half life

Question 14

The quantity of radiation emitted from a source used to describe, used to describe the strength of a source.

Answer 14

activity

Question 15

average lifetime for the decay of radioactive atoms

Answer 15

mean life

Question 16

radioactive sources are placed directly in the targeted tissue where they stay permanently. The radioactive sources decay which might take weeks or months.

Answer 16

permanent brachytherapy

Question 17

the sources are placed for a period of time then removed. This could be for several days at which time the patient is placed in isolation to prevent exposure to others. The brachytherapy procedures you will participate in will have the source in the patients for minutes rather than days before being removed.

Answer 17

temporary brachytherapy

Question 18

point A coordinates

Answer 18

2 cm superior to the top of the ovoids along the tandem

2 cm lateral to the plan of the applicator

Question 19

point B coordinates

Answer 19

2 cm superior to the top of the ovoids

5 cm lateral to the patient midline (parametrial nodes)