Section 2 Computed Imaging

Question 1

construction of a psp cassette and imaging plate

Answer 1

layers:
protective - thin, tough, clear layer
phosphor - traps electrons
reflective - sends light forward when released (black)
conductive - absorbs static electricity
color - between active and support layer (absorbs stimulating light and reflects emitted light)
support - semirigid, provides strength
backing - soft polymer that protects the cassette back

Question 2

what does the photodetector do

Answer 2

amplifies the light released when the laser scans the plate and sends it to an ADC

Question 3

photostimulation process

Answer 3

red laser emitted at 2ev and releases electrons from active layer in the form of blue light at 3ev as they relax into lower levels.
blue light is then read by the photodetector and sent to the ADC

Question 4

reading and erasing the plate process

Answer 4

plate goes through reader, reader scans plate with laser, laser emits light from plate and photodiode collects and sends to aDc.
plate then reaches the great white light and is erased.

Question 5

compare radiographic screen and film speed to PSP

Answer 5

speed of psp is faster but more exposure forgiving
image acquisition psp is faster
psp is moderate resolution (lower than screen)
dqe is better in psp
psp is digital, screen is physical/manual

Question 6

why do you match the body part to the exam

Answer 6

to allow for correct LUT information to be used in adjusting digital brightness and contrast while creating the image

Question 7

selection of technical factors

Answer 7

kVP = penetration
optimal kVp = 60-110
mAs = number of electrons used (amount of paint)

density ^ then penetration and paint ^

Question 8

describe imaging plate and grid selection process

Answer 8

high res plates are for smaller body parts for smaller pixels.

high ratio grid = high accuracy in positioning
focused grid = needs exact distance
parallel = less necesary centering

Question 9

what is the moire effect

Answer 9

when grid lines show on xray in a wavy pattern

Question 10

grid ratio is what

Answer 10

space between lead strips and the height of strips

Question 11

artifact types with PSP plates

Answer 11

Higher artifact risk than flat panel detector (FPD) systems.

Image fading may occur if the plate is not read promptly after exposure.

Double exposure possible if a plate is reused before erasure.

Physical damage artifacts like cracks or light areas may appear on the image.

Image plate artifacts result from poor handling or wear.

Image processing artifacts can occur from incorrect selection of image region.

Reader errors due to faulty laser or erasure lamp may prevent full clearing of previous images.

Printer artifacts include white lines caused by debris on the laser printer mirror.

Operator errors such as improper collimation can lead to incorrect digital exposure calculations.

Question 12

backing layer define

Answer 12

covers the back of the casette

Question 13

what is shuttering

Answer 13

shuttering is putting the black background behind the xray image on the area of the xray that is white (the collimated area)

Question 14

what is bit depth

Answer 14

number of bits per pixel and determines shade of each pixel

Question 15

what is the conductive layer

Answer 15

collects and or realeases extra energy in the plate like a ground wire

Question 16

phosphor layer ingredients

Answer 16

barium flourohalide, chlorohalide, or bromohalide crystals

Question 17

what is phosphor center

Answer 17

the area of the crystals that traps electrons (also known as color center)

Question 18

what helps determine spatial resolution in psp plate makeup

Answer 18

crystal size and thickness of the phosphor layer

Question 19

pattern that laser reads the xray psp plate in

Answer 19

raster pattern

Question 20

define a thin-film transistor flat-panel

Answer 20

introduced in 1995.
is a wireless device used to create imaging that doesn’t need to be read by a laser
made of amorphous silicon and amorphous selenium

Question 21

describe construction of direct indirect TFT flat panel detector

Question 22

differentiate between direct and indirect image capture

Question 23

describe gadolinium oxysulfide detector

Question 24

describe a thalium doped cesium iodide detector

Question 25

relate the design of a TFT flat panel detector to its performance measurements

Question 26

describe the cause of image lag and the correction process

Question 27

what is a dead pixel

Question 28

gain calibration define

Question 29

active-matrix-flat-panel imagers define