Fundamentals of digital radiography

Question 1

CR imaging plate layers

Answer 1

Protective
Phosphor
Conductor
Support
Light Shield
Protective backing

Question 2

Protective layer

Answer 2

protects the phosphor layer

Question 3

Conductor layer

Answer 3

grounds imaging plate from electro-static charge

Question 4

light shield layer/backing layer

Answer 4

prevent unwanted light and background radiation from affecting unexposed latent image

Question 5

Phosphor layer

Answer 5

• made of bromides (85% barium flourohalides, 15% europium iodides)
• store and release energy to create latent image

Question 6

CR digitizer

Answer 6

device used to convert CR latent image into digital radiograph

Question 7

components of CR digitizer

Answer 7

laser - splitter - focusing lens - mirror - photo-multiplier tube - analog to digital converter

Question 8

laser

Answer 8

helium-neon laser interacts with phosphors on imaging plate, releasing light photons

Question 9

photo-multiplier tube

Answer 9

collects photons, sending to ADC

Question 10

analog to digital converter

Answer 10

converts analog (light) signal to digital (binary) signal

Question 11

CR CCD reader

Answer 11

acts as a PMT, but collects and converts to digital all in one step (no ADC needed)

Question 12

photo-stimulating light

Answer 12

erases imaging plate through bright, white light which releases any remaining stored photons

Question 13

DR direct conversion

Answer 13

conversion system with semiconductor and TFT only

Question 14

DR indirect conversion (TFT)

Answer 14

scintilation layer
photodiode layer
TFT array

Question 15

DR indicrect conversion (CCD)

Answer 15

cassetteless conversion system without photocathode or TFT

Question 16

scintillation layer

Answer 16

• made of Cesium Iodide (CsI) rods

- incoming photons converted into light photons

Question 17

photodiode layer

Answer 17

• made of amorphous silicone

- converts light photons into electric charge, transfer to TFT

Question 18

Thin film transistor layer

Answer 18

made of DELs

-converts electric charge to binary

Question 19

sensor chip in CCD system

Answer 19

light photons converted directly to binary and sends to computer for processing

Question 20

semiconductor layer

Answer 20

• amorphous selenium
• interaction between high voltage charge and xray photons causes release of electrons in selenium atoms, which can then go to TFT for processing

Question 21

Pixel size formula

Answer 21

FOV
Pixel size = —————-
Matrix size

Question 22

dynamic range

Answer 22

the range of exposures that can be captured by a detector

Question 23

exposure latitude

Answer 23

the range of exposures that produce quality images at an appropriate patient dose

Question 24

bit depth

Answer 24

total number of brightness levels that can be assigned to any given pixel

Question 25

calculating bit depth

Answer 25

2^(bit system) 8-bit system 2^8 = 256 shades of gray

Question 26

contrast resolution

Answer 26

the smallest exposure change that can be detected and displayed by the system

Question 27

PACS

Answer 27

picture archiving and communication system | -networking and storage system

Question 28

PACS servers

Answer 28

maintain image archives for long-term storage

Question 29

DICOM

Answer 29

digital imaging and communication in medicine | -imaging format that functions on all PACS systems, regardless of vendor or facility

Question 30

EMR

Answer 30

electronic medical record | -contains standard medical data within an office or site

Question 31

EHR

Answer 31

electronic health record | -contain and share information from all providers, not just one office or site

Question 32

server based PACS networking system

Answer 32

imaging equipment to PACS servers to reading stations

Question 33

server based PACS networking system | advantages

Answer 33

- any exam can be opened from any PACS workstation - only one rad can open the exam to interpret it - all prior exams are immediately accessible to rads

Question 34

server based PACS networking system | disadvantages

Answer 34

- PACS server failure=system failure | - data flow can bog-down

Question 35

web based PACS networking system

Answer 35

imaging equipment to PACS servers to reading stations (through the web)

Question 36

web based PACS networking system | advantages

Answer 36

-exams can be accessed from any computer with internet access

Question 37

web based PACS networking system | disadvantages

Answer 37

- desktop monitors may not be of diagnostic quality - speed of this system is dependent on internet speed - PACS server failure=system failure

Question 38

distribution PACS networking system

Answer 38

imaging equipment | to PACS servers and directly to reading stations

Question 39

distribution PACS networking system | advantages

Answer 39

- PACS server failure does not mean system failure | - multiple copies of images

Question 40

distribution PACS networking system | disadvantages

Answer 40

- technologist must send images to correct reading station - rad can only read from their PACS station, would need to physically move to another station to get different images (such as other modalities)