nearpod

Question 1

In a fluoroscopy system with variable mA and fixed kV, the kV setting is determined by:

Answer 1

• the operator manually adjusting the kV values
• selecting the body part being examined, which in turn selects the appropriate kV

Question 2

In terms of mA values used in conventional fluoroscopy, which of the following is true?

Answer 2

mA < or = 5

Question 3

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

Answer 3

reflective layer - pushes any light emitted backwards and pushes it forwards

Question 4

List 2 functions of the lead-lined metal housing surrounding the glass envelope of the image intensifier:

Answer 4

help support
protect and maintain vacuum seal
stops scatter

Question 5

The input phosphor in modern day image intensifiers is made of:

Answer 5

Cesium Iodide

Question 6

Why does an increase in input phosphor layer thickness result in reduced spatial resolution?

Answer 6

Light photons are scattered laterally within the phosphor layer, reducing spatial resolution

Question 7

An increase in. input phosphor layer thickness can result in relatively reduced patient dose. True or false?

Answer 7

true

Question 8

in ALL radiation detectors, radiation is incident on the ________ of the device?

Answer 8

Transducer

Question 9

List 2 basic methods (processes) of operation in radiation detectors

Answer 9

1. the ionization of atoms, which frees up electrons that can be measured as a charge or as a current or a circuit
2. the basis of excitation of electrons, as the electrons return to the pre-excitation stage, they release energy which is captured and transferred into an electrical current

Question 10

list 3 basic modes of detection of radiation detectors

Answer 10

pulse, rate and integrate modes

Question 11

which mode of operation provides the most accurate count of radiation incident on a transducer?

Answer 11

integrate mode - electronic devices can count these events at extremely high speed and with great accuracy

Question 12

true or false, integrate mode detectors require low resolving times

Answer 12

true, need low resolving times to increase accuracy

Question 13

list 2 factors that can improve the sensitivity of a radiation detector

Answer 13

• larger surface area
• increased electronic amplification of incoming signal

Question 14

list 3 ways in which accuracy of radiation detectors can be improved

Answer 14

• increased sensitivity
• range within what we’re looking for
• faster resolving time

Question 15

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

Answer 15

the stopping power of the transducer
- the chemical composition of the transducer and how likely it is to absorb the radiation (higher atomic number is better)

Question 16

what can affect the intrinsic efficiency of a transducer?

Answer 16

• Z of the transducer
• mass density of the transducer
• physical state of the transducer

Question 17

what 2 properties of a transducer affect its absolute detection efficiency?

Answer 17

intrinsic and geometric efficiency

Question 18

which detector operates on the basis of saturation of the detection chamber?

Answer 18

geiger-muller tube

Question 19

what is not found in a photo multiplier tube?

Answer 19

air, the tube is a vacuum

Question 20

what is the thermoluminescent phosphor used for in TLDs?

Answer 20

Lithium fluoride, it is a tissue equivalent

Question 21

what is the primary reason LiF is the phosphor of choice in TLDs?

Answer 21

because it is tissue equivalent (similar Z and density)

Question 22

what is the source of energy applied to LiF to cause it to luminesce?

Answer 22

heat (thermoluminescence) annealing oven

Question 23

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

Answer 23

the curved anode

Question 24

what is the purpose of output phosphor?

Answer 24

phosphors will create light so it turns electrons into light

Question 24

the acceleration of electrons to a higher kinetic energy within the image intensifier contributes to?

Answer 24

Flux gain and brightness gain

Question 25

When using a mobile fluoroscopic machine with a fixed SID, geometric image magnification can be achieved by increasing the OID, Tru or false?

Answer 25

true, any time you increase OID you get geometric magnification

Question 26

If the brightness gain of a 25cm II tube is 8000, what is the flux gain of the system with an output phosphor size of 2.5cm?

Answer 26

brightness gain = flux gain x minification gain 8000 = F x (25/2.5)^2 F = 80

Question 27

A 17cm II tube has a flux gain of 120 and a 2.5 cm output phosphor. If the conversion factor of an II os equal to 0.01 times the brightness gain, what is this II's conversion factor?

Answer 27

Brightness gain = flux gain x minification gain BG = 120 (17/2.5)^2 BG = 5548.8 Conversion factor = BG(0.01) CF = 55.488

Question 28

What is conversion factor?

Answer 28

how much light you get out of it compared to the rate of dose that's hitting it

Question 29

magnification during a fluoroscopic procedure result in?

Answer 29

Increased spatial resolution

Question 30

veiling glare in II's is the result of/

Answer 30

Scatter inside the image intensifier

Question 31

How is patient dose affected, and by what factor does it change when IP size is changed from 25 cm to 10 cm?

Answer 31

increases patient dose = (ip old/ip new)^2 = (25/10)^2 = 6.25