Practice questions

Question 1

Where is all radiation incident?

Answer 1

Incident on ALL transducers

Question 2

List 2 basic methods/processes of operation in radiation dectors?

Answer 2

1. Ionize it by interacting with atoms
2. Excitation

Question 3

List 3 basic modes of operation of radiation detectors:

Answer 3

1. Pulse
2. Rate
3. Intograte

Question 4

What modes of radiation detector operation allows for the detection of raidation?

Answer 4

1. Pulse
2. Rate
3. Intograte

Question 5

Which of the modes of operation provides the most accurate count of raidation incident on a transducer? Why?

Answer 5

Integrate mode; because it counts the total amount of radiation even if the radiation if fluxuating

Question 6

Why is it important to know the rate even though its not completely accurate?

Answer 6

Because it allows for detection of the amount of radiation to notify you on general intensity

Question 7

True or false?

Integrate mode detectors require low resolving times.

Answer 7

True

Question 8

List 2 factors that can improve the sensitivity of a radiation detector:

Answer 8

1. Increase the size of the ion chamber/DELs
2. Amplify the signal (it can also lower the dose to the patient)

Question 9

List 3 ways in which accuracy of radiataion detectors can be improved:

Answer 9

1. Increase sensitivity
2. Low resolving time
3. Range that it will be able to detect

Question 10

What is meant by the term “intrinsic efficiency” of a transducer?

Answer 10

Inherent to the material itself, not other enviormental factors, it is how well the radiation is detected/the stopping power

Question 11

What can affect the intrinsic efficancy of a transducer?

Answer 11

a. Atomic number of transducer elements
b. Mass density of transducer elements
c. Physical state of transducer material

Question 12

What 2 properties of a transducer effect it’s absolute efficiancy?

Answer 12

1.Intrinic efficiency
2.Geometric efficiancy

Question 13

What operates on the basis of saturation of a detection chamber?

Answer 13

Gieger muller tubes

Question 14

Which is not found in a PMT and why?
a. Anode
b. Dynode
c. Photocathode
d. Air

Answer 14

D; we dont want air interacting with the tube photons

Question 15

What is the element used in thermoulminescent phosphor TLDs?

Answer 15

Lithium floride

Question 16

What is th primary reason LiFl is the phosphor of choice in TLDs?

Answer 16

It is simular in Z# and denisty to human tissue

Question 17

What is the source of energy applied to LiFL to cause its luminescence?

Answer 17

Heat by annealing

Question 18

What term is used to describe any residual latent image on the CR following processing?

Answer 18

Ghosting

Question 19

How is ghosting resolved in CR plates?

Answer 19

Flooded with a very intense whhite light to give e- energy to escape the F traps

Question 20

Explain the term fading with respect to CR cassettes:

Answer 20

The natural dropping of e- from F centers over time from not processing the latent image

Question 21

List the ways in which the emmission efficancy in conventional PSP CR plates has been improved:

Answer 21

1. Needle shaped phosphor
2. Reflective layer
3. Barium floride dopped with eroupium

Question 22

In floro with variable mA and fixed kV, the kV setting is determined by what?

Answer 22

1. Manually choosing KV
2. Choosing the body part

Question 23

In terms of conventional floro, what should the mA be?

Answer 23

Less than 5 mA

Question 24

In the input phosphor, what gets converted into what?

Answer 24

X-rays, light

Question 25

What is the purpose of the aluminum substrate coated on the external surface of the input phosphor?

Answer 25

To take any photons travelling backwards and reflect it forward to the photocathode

Question 26

What is the input phosphor made of?

Answer 26

Cesium iodide

Question 27

Why does an increase in thickness in the input phosphor layer result in reduced SR?

Answer 27

More diverging photons

Question 28

# T/F? An increase in phosphor thickness can result in relatively reduced dose;

Answer 28

True, better at absorption so you can use decrease in dose

Question 29

What feature ensures that all photoelectrons travel the same distance to the focal point within the II?

Answer 29

The curve of the IP

Question 30

The pupose of the OP is what?

Answer 30

To turn electrons into light

Question 31

The acceleration of e to a higher KE within the II contributes to what?

Answer 31

Fulx and brightness gain

Question 32

# T/F When using mobile floro with fixed SID, geometric mag can be achieved by increasing OID.

Answer 32

True

Question 33

With a brightness gain of 8000 in a 25 cm input phosphor, what is the flux gain if the output phospor size is 2.5 cm?

Answer 33

FG=80

Question 34

What does magnification in floro result in?

Answer 34

Increase in SR

Question 35

What is S distoriton due to?

Answer 35

External magnetic feild

Question 36

What is veiling glare a result of?

Answer 36

Scatter

Question 37

What is the conversion factor? 17 cm II tube Flux gain=120 Output phosphor=2.5cm

Answer 37

55.5