Ch 4 Photostimulable Phosphor Image capture

Question 1

What is one way of acquiring and processing digital radiographic images?

Answer 1

with photostimulable phosphor systems (PSP)

Question 2

Are PSP cassette based or cassette less?

Answer 2

they are both

Question 3

Basically describe a PSP cassette

Answer 3

the cassette is a lightproof container that protects an imaging plate from light and handling

Question 4

The PSP imaging plate takes the place of the radiographic film and is capable of …

Answer 4

storing an image formed by incident x-ray photon excitation of phosphors

Question 5

During the reading process of a cassette-less PSP system, the phosphor…

Answer 5

releases the stored light and converts it into an electrical signal, which is then digitized.

Question 6

The PSP cassette looks like…

Answer 6

a conventional screen/film cassette.

Question 7

The PSP cassette consists of…

Answer 7

a durable, lightweight plastic material. The cassette is backed by a thin sheet of aluminum or lead and contains an antistatic material (felt)

Question 8

What is the function of the aluminum or lead that backs the PSP cassette?

Answer 8

it absorbs backscatter x-ray photons

Question 9

What is the function of the antistatic material?

Answer 9

it protects against static electricity buildup, dust collection, and mechanical damage to the plate

Question 10

In PSP systems the image is recorded on…

Answer 10

a thin sheet of plastic known as the imaging plate

Question 11

How many layers does an imaging plate have?

Answer 11

7

Question 12

What are the layers of the imaging plate?

Answer 12

1. protective layer
2. phosphor layer
3. reflective layer
4. conductive layer
5. color layer
6. support layer
7. backing layer

Question 13

What is the protective layer of the PSP plate?

Answer 13

a very thin, tough, clear plastic that protects the phosphor layer

Question 14

What is the phosphor layer also known as?

Answer 14

the active layer

Question 15

Explain the phosphor layer.

Answer 15

It is a layer of photostimulable phosphor that traps electrons during exposure. It is usually made of phosphors from the barium fluorohalide family. This layer may also contain a dye that differentially absorbs the stimulating light to prevent as much spread as possible and functions much the same as dye added to conventional radiographic screens.

Question 16

What is the reflective layer?

Answer 16

a layer that sends light in a forward direction when released in the cassette reader. This layer may be black to reduce the spread of stimulating light and the escape of emitted light. Some detail is lost in this process.

Question 17

What is the conductive layer?

Answer 17

a layer of material that absorbs and reduces static electricity.

Question 18

What is the color layer?

Answer 18

it is on newer plates and located between the active layer and the support, that absorbs the stimulating light but reflects emitted light

Question 19

What is the support layer?

Answer 19

a semi-rigid material that gives the imaging sheet some strength

Question 20

What is the backing layer?

Answer 20

a soft polymer that protects the back of the cassette

Question 21

What does a PSP cassette have on the back?

Answer 21

a window with a barcode label or barcode sticker to allow the tech to match the image information with the patient ID code

Question 22

A PSP cassette may also have a color coded sticker for what reason?

Answer 22

to indicate the appropriate orientation of the cassette in relation to the patient

Question 23

With a PSP system, how is the exposure recorded?

Answer 23

The remnant beam interacts with electrons in the barium fluorohalide crystals contained within the imaging plate. The interaction stimulates, or gives energy to, electrons in the crystals, trapping them in an area of the crystal known as the color or phosphor center.

Question 24

How long will the trapped signal remain on the PSP plate?

Answer 24

for hours or even days…actually, the image never goes away, it just isn’t seen

Question 25

How many different PSP READERS? what are they?

Answer 25

2; point scan and line scan

Question 26

What do point scan readers have?

Answer 26

an optical stage, a scanning laser beam, translation mechanics, a light pickup guide, a photomultiplier, a signal transformer/amplifier, and an analog to digital converter (ADC)

Question 27

In a point scan reader how many laser points radiate this imaging plate?

Answer 27

only one

Question 28

Line scan readers are based on what?

Answer 28

simultaneous stimulation of the imaging plate one line at a time

Question 29

How is the acquisition done with a line scan reader.

Answer 29

with a charge coupled device (CCD) linear array photodetector.

Question 30

What does PSL stand for?

Answer 30

photostimulated luminescence

Question 31

What is PSL?

Answer 31

the emission of light from the phosphor layer after stimulation by the relevant light source

Question 32

Unlike the point scan reader, the line scan uses what to scan?

Answer 32

a scanning module that contains several linear laser units and optical light collection lenses. The line scan system requires a lens array to focus each laser beam to a corresponding point on the CCD array.

Question 33

What are the 2 scan directions in a PSP reader?

Answer 33

1. fast scan direction

2. slow scan direction

Question 34

What is fast scan direction?

Answer 34

the movement of the laser across the imaging plate known as scan

Question 35

What is slow scan direction?

Answer 35

the movement of the imaging plate through the reader known as translation or sub-scan direction

Question 36

What does laser stand for?

Answer 36

light amplification of stimulated emission of radiation

Question 37

What does coherent light mean?

Answer 37

it is coherent because all of the photons are traveling in the same direction at the same frequency

Question 38

What does the photodetector do in the PSP reader?

Answer 38

it amplifies the light and sends it to an ADC.

Question 39

Why does the translation speed of the plate have to be coordinated with the scan direction of the laser?

Answer 39

If not, the spacing of the scan lines will be affected