Physics Test 2 - digital image processing💕

What does computed radiography (CR) use?

Uses photostimulable storage phosphor imaging plate (PSP) typically inside a cassette

Does digital radiography (DR) use photostimulable phosphors (PSP) like CR?

NO, do not use

Direct conversion

Doesn’t use scintillation

Indirect conversion

uses scintillation

What is the two part process of indirect systems?

1. Xray photon converted to light

2. Then converted to an electrical signal

A _____ converts incoming xray photons to light (indirect conversion)

Scintillator

Photodetector converts light to electronic signal (indirect inversion) The photodetector can either be:

• A Charged Coupled Devices (CCD)

  OR

• A Amorphous silicon with a TFT

Direct Conversion

Use amorphous selenium and a TFT

_____ collects and processes the electrical charge

TFT

What does DICOM stand for?

Digital imaging and communication in medicine

Production of x-ray image is ____ or in voltage fluctuations in a wave forms

Analog

Computers operates on ____ machine language

binary (digital)

Analog is converted to digital by ____

Analog-to-Ditigal Conversion (ADC)

Bit

each binary number, 0 or 1 (binary digit)

Byte

an 8-bit word

Matrix

Series of boxes

• Rows and columns

• Each box has a numerical value that can be transformed into brightness or density level

Pixel

Individual matrix box
– For picture elements
– Each has an address

Voxel

each pixel represents a 3-dimensional volume of tissue

FOV

Field of view

• Overall dimension of the image matrix

• DR FOV determined by the size of detector and by collimation

Greater matrix size for same FOV has better

spatial resolution (image sharpness), because of smaller pixels

Number of shades of gray is determined by the

grayscale bit depth

Point Processing Operations

• Involves adjusting the value of an input pixel (point) to the corresponding output pixel.

• The most common processing operation

• Is done between input from the image receptor & output image that is viewed on the monitor

Histogram

generated during initial processing

If exposure is outside range of exposure, computer will correct the image by shifting the histogram, this is called

Rescaling

What is applied for a standard contrast to the exam

LUT or Look UP Table

*LUT will provide proper grayscale regardless of variations in kVp and mAs.

Windowing

• Changes contrast and brightness on the monitor

• Controlled by varying the numerical values of each pixel

What is window width?

range of shade of gray that will be displayed (contrast numbers)

What is window level

controls the brightness of the image

Kernel

Defined as those in which mathematical calculations are applied to only a small group of pixels

What does spatial frequency filtering do?

Sharpen, smooth, blur, reduce noise, or pull elements of interest from an image

frequency domain

the computer uses the Fourier transformation algorithm

location domain

the pixel values themselves are used

High pass filtering (edge enhancement)

• Convert image to spatial frequency domain

• High pass filter removes low spatial frequency

• Produces a sharper output image

  Example; contrast filled vessels, enhances edges

Low pass filtering (smoothing)

• Similar process to intentionally blur the image

• Reduces noise and displayed brightness level of pixel

• Decreases image detail

• Even though image is blurred, it is smooth

Unsharp masking (blurring)

• Subtracts a low-pass filtered (blurred) image from the original imag

• Produces a sharper image

Spatial location filtering (convolution)

kernel applied repeatedly over pixels, which changes the value of the pixel
• Smooths, Sharpens, Intensifies, or Enhances

What does spatial resolution control?

Detail, sharpness and recorded detail

• Controlled by matrix size & number of pixels

What is the relationship between matrix size, pixel size and spatial resolution?

As matrix size increases, pixel size decreases, spatial resolution (detail) increases

Density resolution

Part of grayscale bit depth

How is noise measured?

signal-to-noise ratio (S/N)

Detective Quantum Efficiency

Measure of sensitivity & accuracy image receptors have when converting data to
output viewing device

What are Exposure Indicators ?

They reflect the quantity of photons that hit the Image detector

Exposure Index (EI)

Directly proportional to radiation striking the imaging plate

S number

Inversely proportional to exposure reaching plate

deviation index (DI)

A comparison between the actual exposure & the proper exposure received by the image detector