RADSCI 202 Exam 2

scanning, sampling, quantization

What are the 3 steps of digitalization

sampling

taking intensity measurements from each pixel or cell in an image

scanning

dividing of the field of the image into an array of cells or pixels to format the image

quantization

assigning digital values to each measurement from the pixels of an image matrix

spatial resolution

Pixel pitch determines __ __

grayscale

Bit depth determines __

efficiency

DQE determines detector __

amorphous selenium

Direct DR is made up of __ __

scintillator, amorphous silicon

 Indirect DR is made up of a __ + __ __

F-centers

CR stores image in ____

charge

 Image data stored as __ in capacitor

spatial resolution

Pixel size limits __ __

Encoding

Converting numerical values into binary code (0s and 1s).

pixel

smallest digital image element assigned a brightness value.

pixel pitch

Distance from the center of one pixel to the next pixel.

Matrix Size, Bit Depth

File Size Formula: File Size =__ __ x __ __

2, bit depth

Bit Depth Formula: __^__ __ (8‑bit = 256 gray levels).

contrast

Window Width controls image __

more black and white, high contrast

narrow window width =

more shades of grey, low contrast

wide window width =

brightness.

Window Level controls image __

brighter (whiter) image

decreased window level =

darker (black) image

increased window level =

processing

In digital imaging, brightness is controlled primarily by __, not solely by kVp or mAs

DQE

Ability of a detector to absorb x‑rays/light and convert them into useful image signal.

signal to noise, lower

Higher DQE → better __ to __ ratio and __ patient dose.

Dexel (DEL)

Individual detector element in a DR plate.

data, gate

Active Matrix Array contains __ lines and __ lines.

Thin Film Transistor (TFT)

__ __ __ acts as a switch during readout.

capacitor

Charge from exposure is stored in a __.

Direct DR

Uses amorphous selenium (a‑Se). Converts x‑ray → electrical signal.

Indirect DR

Uses scintillator (CsI or Gd2O2S) + amorphous silicon. Converts x‑ray → light → electrical signal.

F‑centers

___ trap excited electrons to store the latent image.

white

During CR plate erasure bright __ light clears remaining trapped electrons.

Ghosting

Residual image left on the plate after exposure.

Photomultiplier

A __ tube converts light photons into amplified electrical signal

Pixel size

__ __ is the limiting factor for spatial resolution in digital imaging.

sharper

Higher Nyquist frequency results in __ spatial resolution.

fill factor

__ __ is that percentage of the detector element devoted to photon absorption.

DQE, lower, better

Higher fill factor → higher __ and __ exposure needed and __ spatial resolution

phosphorescence, proportionally

__ is the blue-violet light that happens when stimulated by the CR reader and it is __ to the radiation originally received

fluorescence

during exposure the blue-violet light you can see is __

europium, F-centers

these crystals: flourobromide and fluorchloride are doped with __ and are what create __

fast scan

__ __ is the movement of the laser across the imaging plate

slow scan

__ __ is the movement of the imaging plate, slowly and consistently

stimulation

fast scan and slow scan both happen in which stage of creation

1) exposure

2) stimulation/laser

3) read and digitize

4) erasure

List the four steps of creation of CR

increased, decreased, increased

In direct DR there is __ spatial resolution, __ DQE and __ dose

decreased, increased, decreased

In Indirect DR there is __ spatial resolution, __ DQE and __ dose

Indirect

Is indirect or direct DR more preferred

more, lower

In regards to pixel pitch, less pixels and __ distance = __ spatial resolution

less, higher

In regards to pixel pitch, more pixels equals __ distance which = __ spatial resolution

more, better

increased bit depth means __ gray levels which = __ contrast resolution

less, worse

decreased bit depth means __ gray levels which = __ contrast resolution

PSP crystal

What is letter A

Protective Overcoat

What is letter B

Binder

What is letter C

phosphor layer

What is letter D

reflective layer

What is letter E

Base

what is letter F

Antistatic layer

What is letter G

Lead

What is letter H

antistatic

the __ layer prevents backwards/forwards movement