Digital Radiography Chapter 2

Front 1

What is an Analog image

Back 1

Radiology image obtained through continuous scanning by a light source transmitted through an image onto a photomultiplier tube that generates an analog output signal

Front 2

What is an Analog-to-Digital Converter (ADC)

Back 2

Device that converts an analog signal ( electrical) into a digital signal ( bits)

Front 3

What is Bit depth?

Back 3

Number of bits per pixel

Front 4

What is convolution?

Back 4

An example of filtering in the spatial location domain

Front 5

What is density resolution?

Back 5

The effect of bit depth on the number of shades of gray in an image

Front 6

What is a digital image?

Back 6

Numerical representation of computer processing of digital data

Front 7

What is digital image processing?

Back 7

Computer processing of digital data into a numerical representation of the patient that must then be converted to an analog image for human viewing

Front 8

What is the Field of View (FOV)?

Back 8

Size of the matrix selected by the operator for examination depending upon the dimensions of the anatomy to be imaged

Front 9

What is the Fourier transform?

Back 9

Converts a function In a time domain to a function in the frequency domain

Front 10

What is a geometric operation?

Back 10

In image processing, allows the user to change position or orientation of pixels in an image in order to enhance diagnosis

Front 11

What is the Global processing operation?

Back 11

All the pixels in the entire input image are used to change the value of a pixel in the output image

Front 12

What is Gray-scale processing?

Back 12

Processing of an image that includes spatial filtering,image subtraction and temporal averaging

Front 13

What is a Histogram?

Back 13

A graph of the number of pixels in an image having the same density values plotted as a function of the gray levels

Front 14

What is image analysis?

Back 14

Digital image processing in which measurements and statistics are performed in addition to image segmentation, feature extraction and classification of objects

Front 15

What is image compression?

Back 15

Reduction in the size of a digital image in order to decrease transmission time and reduce storage space

Front 16

What is image enhancement?

Back 16

Improvement of image quality for the purpose of viewing needs , including contrast and edge enhancement, spatial and frequency filtering,image combining and noise reduction

Front 17

What is image restoration?

Back 17

Improvement in quality of image that has distortions or degradations ; ex sharpening a blurred image

Front 18

What is image synthesis?

Back 18

Creation of a composite image from other images or non image data

Front 19

What is the Inverse Fourier transform?

Back 19

Transforms an image in the frequency domain back to the spatial location domain for viewing

Front 20

What is the Local processing operation?

Back 20

The output image pixel value is obtained from a small area of pixels around the corresponding input pixel: includes spatial filtering, edge enhancement and smoothing

Front 21

What is lossless compression?

Back 21

Aka reversible compression in which no information is lost in the compression process

Front 22

What is lossy compression?

Back 22

Aka irreversible compression, in which information is lost in compression process not generally used in primary diagnosis due to reliability

Front 23

What is low pass filtering?

Back 23

Uses low-pass filter on input image to reduce noise (smoothing), creating a blurred output image

Front 24

What is the Matrix?

Back 24

A two- dimensional array of numbers that makes up a digital image

Front 25

What are pixels?

Back 25

(Picture element) small square regions in an image containing a discreet value that represents a brightness level reflecting the tissue characteristics being imaged

Front 26

What is Pixel size?

Back 26

Calculated using the relationship pixel size=field of view/ matrix size. In digital imaging, the larger the matrix, the smaller the pixel size,means better spatial resolution

Front 27

What is Quantization?

Back 27

Process by which brightness levels obtained from sampling are assigned an integer , known as the gray level

Front 28

What is sampling?

Back 28

Measurement of pixel brightness level

Front 29

What is scanning?

Back 29

Division of an image into an array of pixels

Front 30

What is the Spatial Frequency Domain?

Back 30

Domain in which images are acquired and described according to the wavelength of the signal used to acquire the image

Front 31

What is Spatial location domain?

Back 31

Domain in which an image is described using right handed X-Y coordinates

Front 32

What is Spatial location domain?

Back 32

Domain in which an image is described using right handed X-Y coordinates

Front 33

What is Spatial resolution?

Back 33

Sharpness of an image

Front 34

What is unsharp masking?(blurred)

Back 34

Subtracts the blurred image produced by the low-pass filtering process from the original image, resulting in a sharp image

Front 35

What is a Voxel?

Back 35

(Volume element) the information contained in a volume of tissue that is converted into numerical values and expressed in pixels

Front 36

What is Window leveling? (WL)

Back 36

The center of the range of numbers in a digital image Controls Brightness

Front 37

What is window width?(WW)

Back 37

The range of numbers in a digital image

Controls Contrast

Front 38

What is windowing?

Back 38

Digital image processing technique used to change the contrast (controlled by the window width) and brightness (controlled by the window level) of an image