Physics

Question 1

What is a Patterson-Parker System?

Answer 1

Means you have a non-uniform source distribution to give a uniform dose distribution meaning you have rules for loading

Question 2

What is a quimby system?

Answer 2

A uniform source distribution of uniform strength resulting in a nonuniform dose distribution

Question 3

Intracavitary GYN implant point A

Answer 3

Point where uterine vessels cross ureter, about 2 cm up and out. Region of maximum radiation sensitivity

Question 4

Intracavitary GYN implant point B

Answer 4

Obturator nodes, about 2 cm up and 5 cm from uterine canal

Question 5

How many half lives do you need to hold a source for decay?

Answer 5

10 half lives

Question 6

The Clarkson method is used for

Answer 6

irregularly shaped treatment fields

Question 7

In which interaction is the energy of an incident photon completely transferred to an atomic electron (usually inner shell)?

Answer 7

photoelectric effect

Question 8

When calculating shielding thickness needed for a linear accelerator treatment room, the term “use factor” is used to describe the:

Answer 8

fraction of the time the beam is directed toward the barrier

Question 9

A fractionated treatment regimen results in more damage to the tumors than the same total dose given in a single fraction because:

Answer 9

Reoxygenation of hypoxic cells

Question 10

The most commonly used material for thermoluminescent dosimeters is

Answer 10

Lithium fluoride

Question 11

“Quality” used interference to a beam of radiation refers to

Answer 11

the penetrating power of the beam

Question 12

Well chamber

Answer 12

Used to calibrate brachy sources

Question 13

Gantry, collimator and table rotation creates what effect in film

Answer 13

Starburst

Question 14

Multiple beam alignment check?

Answer 14

Double expose film using beam 180* apart, blocking the other half

Question 15

What is beam flatness?

Answer 15

Constancy if intensity across 80% of the beam profile

Question 16

Dosimeter QA tests

Answer 16

Flatness, outpu

Question 17

Mechanical QA tests

Answer 17

Distance, lasers, light/radiation coincidence

Question 18

Why is a split field test done?

Answer 18

Check stability of isocenter

Question 19

What is a disadvantage in using a Cobalt 60 beam for radiation therapy treatment?

Answer 19

The large penumbra

Question 20

Half-life of Cesium 137

Answer 20

30 Years

Question 21

Half-life of Au-198

Answer 21

2.7 days

Question 22

Half life of Palladium 103

Answer 22

17 Days

Question 23

Half-life of Iodine 125

Answer 23

59.5 Days

Question 24

Half-life of Radium 226

Answer 24

1600 years

Question 25

A superficial machine has what energy range?

Answer 25

50-150 kVp energy beam

Question 26

A hardened photon beam will have a

Answer 26

Higher HVL and higher penetrating power

Question 27

The interactions in matter caused by lower energy linacs (4-6 MeV) are primarily of what type?

Answer 27

Compton scattering

Question 28

The CT simulator operates at beam energies that interact primarily in tissue by:

Answer 28

photoelectric effect

Question 29

n order for positron emission to occur, the available nuclear energy must be at least:

Answer 29

1.02 KeV

Question 30

What is the daily CT number accuracy (for water) tolerance of a CT scanner?

Answer 30

5 HU

Question 31

What is the monthly testing tolerance of table vertical and longitudinal motion of a CT scanner?

Answer 31

1 mm

Question 32

Gantry and collimator indicators have a tolerance of:

Answer 32

1 degree

Question 33

What would you use to measure radiation output during annual calibration of a linear accelerator?

Answer 33

Water phantom or an ionization chamber