Ch. 21

Front 1

These are a finite set of instructions used by computers to compute a desired result

Back 1

Algorithms

Front 2

Unwanted image abnormalities, such as blurring, star, and beam hardening. Can be caused by patient motion, Anatomy, design of the scanner, or system failure.

Back 2

Artifacts

Front 3

With CT scanners there are several ways that dose or exposure is represented. CTDI is normalized value that is computed for measurements on a standard Phantom, displayed in milligray.

Back 3

Computer tomography dose index

Front 4

A system that serves three functions: the transmitted radiation beam is measured, measurements are encoded to binary, in the binary data is transmitted to the computer.

Back 4

Data acquisition system (DAS)

Front 5

Solid state detectors in a CT scanner are designed to convert radiation to light

Back 5

Detectors

Front 6

Commonly used method of reconstructing CT data. It is also called the summation method.

Back 6

Filtered back projection

Front 7

Also called CT numbers, which range from + 1000 - -1000. These represent various tissue densities and linear attenuation coefficients.

Back 7

Hounsfield units (HU)

Front 8

Techniques that reduce the noise and artifacts present in a CT reconstructed image.

Back 8

Iterative reconstruction

Front 9

Refers to the ability to see differences in objects that are of similar Shades of Grey in tissue.

Back 9

Low contrast resolution

Front 10

Images seen on the screen right display of cells in rows and column.

Back 10

Matrix CT

Front 11

This is the grainy appearance of an image

Back 11

Noise

Front 12

Used in spiral CT, it is determined by the couch movement in the longitudinal Direction during one rotation of the Gantry, divided by the slice thickness.

Back 12

Pitch

Front 13

Small, discreet elements that make up an image.

Back 13

Pixels

Front 14

The process in which the CT computer analyzes and processes the information received from the detectors and displays it on a TV monitor.

Back 14

Reconstruction

Front 15

Area for which projection data is collected for a CT scan is determined by the scan field of view. It helps to position the patient in the center of the CT bore so the patients Contour is not cut off laterally and is centered in the scan field of View.

Back 15

Scan field of view

Front 16

This is a CT reconstruction parameter that determines the thickness of reconstructed images.

Back 16

Slice thickness

Front 17

This is a CT reconstruction parameter that determines the distance between the center of CT slices

Back 17

Slice increment

Front 18

CT x-ray tube and detector can continue to rotate around the patient without concern of cables become entangled because of these, which are metal strips carrying electronic signals and power that is swept up by special metal brushes

Back 18

Slip ring

Front 19

Refers to the clarity or measure of detail in a CT image

Back 19

Spatial resolution

Front 20

Also referred to as helical CT. Patient is position at a fixed point, and while the X-ray tube is rotating, the patient moves into the aperture to create a skin pattern that resembles a slinky or coil spring

Back 20

Spiral computed tomography

Front 21

The ability to freeze or decrease motion of the scanned object, especially in 4D CT simulation

Back 21

Temporal resolution

Front 22

Volume elements

Back 22

Voxel

Front 23

Represents the central hounsfield unit of all the CT numbers within the window width

Back 23

Window level

Front 24

Range of numbers displayed or the contrast on a CT image

Back 24

Window width