CT Basics


Terms in this set (...)

Imaging system
X-ray tube
Detector Electronics
What is located in the operators room?
Display system
Recording System
Stoarge System
CT System
Host Computer
Storage Device
Scan Controller
High voltage generator
S and H
Array Processor
Image Display
CRT flat display
LCD flat panel display
Images are diisplayed in gray scale
Operating System
Controls the hardware components
Controls the operation of the computer
Enables the computer to run other programs
Allows for multi-tasking, multi-processing, and multi-programming
Major Program in Operating System
Resides in primary memory
Controls all other portions of the operating system
CT Software
Pre processing
Post processing
Corrects the data collected from the detectors before the data is sent to reconstruction
Builds up the image from raw data
Operates on the reconstructed images that are being displayed
Electronic networking
Ensures the transfer of data and images
Uses the DICOM standard
Digital Imaging and Communications in Medicine
Host Computer
Primary link between the tech and other components of the imaging system
Translates commands entered at the console by the tech into computer language and passes it on to scan controller or storage device
Storage Device
Stored in a digital form
Stored in 2D pixel arrays
Typical matrix is 512 by 512 X 8 bytes
One image needs 0.5MB of storage
80 images needs 40MB of storage
Store on magnetic tape, optical disks, CD
Scan Controller
Responsible for the timing of the gantry, table, and high voltage generator
High Voltage Generator
Produces the high voltage potential that exists between the cathode and anode
Small, solid state, high frequency
Mounted on a rotating frame
Housed in the gantry
80 to 140 kV and 20 to 500 mA
Digital to Analog converter
Converts electronic signals (digital?) sent from the scan controller to the gantry control into analog form
Houses the X-ray tube, detectors, and data aquistion system
Cooling is a prime consideration
Aperature 70 cm, 50 cm of scan area
Tilts 12 to 30 degrees in either direction
CT X-ray Tube
Mounted on a rotating frame
Rotates around the patient
Emits X-rays in a continuous stream
Works the same as an x-ray tube (cathode to anode)
mA- number of photons (current)
kV- energy of the photon (voltage)
Anode is made of tungsten
Cathode has the filaments with different lengths
Small focal spot uses small filament for a narrow beam resulting in thin slice high resolution
Patient Table
Made of carbon fiber
Patient Coordinate System
Patient is lying with head in first in a supine postion
X axis- right to left
Y axis- anterior to posterior
Z axis- superior to inferior
Measurements are made by the detectors
The attenuated information is converted to electical signals
These electrical signals pass through the amplifier
S and H
Sample and Hold Component
The analog electrical signals are sampled
Analog to digital converter
The amplified electrical signals are digitzed
Array Processor
Stores the raw data file
(May be available for a week or more)
Calculates the image seen on the console
Independent manipulation of data, including raw data
2 Characteristics of a Minicomputer
Large storage capacity
Fast and efficient processing of data