CT 1 (parts + important terms)

Gantry Aperture

1

Microphone

2

Sagittal Laser Alignment Light

3

Patient Guide Light

4

X-Ray Exposure Indicator Light

5

Emergency Stop Buttons

6

Gantry Control Panels

7

External Laser Alignment Lights

8

Patient Couch

9

ECG Gating Monitor

10

X-Ray Tube

1

Filters, Collimator

2

X-ray Tube Heat Exchanger (Oil Cooler)

4

High Voltage Generator (0-75 kV)

5

Direct Drive Gantry Motor

6

Rotation Control Unit

7

Data Acquisition System (DAS)

8

Detectors

9

Slip Rings

10

Detector Temperature Controller

11

High Voltage Generator (75-150 kV)

12

Power Unit (AC to DC)

13

opening of the gantry through which the patient passes during the scan

Aperture

Preset amount of radiopaque contrast medium injected rapidly per IV administration to visualize high-flow vascular structures, usually in conjunction with dynamic scan; most often injected using a pressure injector

Bolus

In multidetector CT, multiple rows of detectors are arranged along the longitudinal (z) axis of the patient. Each detector row consists of numerous elements

Channel

Arbitrary number assigned by computer to indicate relative density of a given tissue; CT number varies proportionately with tissue density

CT number

Image distortion caused by combination of table indexing and respiration; table moves in specified increments, but patient movement during respiration may cause anatomy to be scanned more than once or not at all.

Image misregistration

Spatial resolution of a voxel in which all three axes of the volume element are equal. Slice thickness is equal to pixel size

Isotropic spatial resolution

assignment of appropriate gray level to each pixel in an image

Mapping

Instructions for CT examination specifying slice thickness, table incre-ments, contrast administration, scan diameter, and any other requirements specified by the radiologist.

Protocol

Ability to process or reconstruct incoming data in milliseconds.

Real time

Process of creating a digital image from raw data.

Reconstruction

Process of changing the shading of a three-dimensional image; commonly used to increase depth perception of an image.

Rendering

Actual rotation of x-ray tube around the patient; used as a generic reference to one slice or an entire examination.

Scan

Also referred to as the zoom or focal plane of a CT scan; predetermined by the radiographer to include the anatomic area of interest; determines FOV.

Scan diameter

Amount of time used to scan an entire volume during a single spiral scan.

Scan duration

X-ray exposure time in seconds.

Scan time

Method of cropping or editing target objects from image data.

Segmentation

One scan through a selected body part; also referred to as a cut; can vary from 0.35 mm to 1 cm, depending on the exam

Slice

low-voltage electrical contacts within the gantry designed to allow continuous rotation of an x-ray tube without the use of cables connecting internal and extenders component

Slip ring

Individual pixel with the associated volume of tissue based on the slice thickness.

Voxel

controls the overall gray level and affects image contrast

Window width

controls subtle gray images within a certain width range and ultimately affects the brightness and overall density of an image

Window level