BIOMEDICAL ENGINEERING SYSTEM

Title:

COMPONENTS OF CT SCANNER

ENGR KHALEEQUE AHMED

SIR SYED UNIVERSITY OF ENGINEERING &

TECHNOLOGY KARACHI

CT Gantry External View1.gantry aperture (720mm diameter)2.microphone3.sagittal laser alignment light4.patient guide lights5.x-ray exposure indicator light6.emergency stop buttons7.gantry control panels8.external laser alignment lights9.Patient couch10.ECG gating monitor

CT Gantry internal View1. x-ray tube

2. filters, collimator, and reference

detector

3. internal projector

4. x-ray tube heat exchanger

5. high voltage generator (0-75kV)

6. direct drive gantry motor

7. rotation control unit

8. data acquisition system (DAS)

9. Detectors

10.slip rings

11.detector temperature controller

12.high voltage generator (75-

150kV)

13.power unit (AC to DC)

14.line noise filter

GANTRY

The Gantry includes the

The X-ray tube

The Detector Array

The High-Voltage generator

The patient Support Couch

THE X-RAY TUBE

CT x-ray tubes are very large.

They have an anode heat storage capacity of 8 MHU (million heat unit) or more.

They have anode-cooling rates of approx 1MHU per minute because the anode disc has a larger diameter, and it is thicker.

THE DETECTOR ARRAY

CT imaging system have multiple detectors in an array that numbers up to tens of thousands.

Previously gas-filled detectors were used, but now, all are scintillation, solid state detectors.

Early scintillation detector arrays contained scintillation crystal-photodiode assemblies because photodiodes convert the light into an electronic signal..

CONTINUED

The combination of a scintillation crystals and the light detector is called a scintillation detectors.

The concentration of detectors is an important characteristic of a CT imaging system that affects the spatial resolution of the system.

COLLIMATION

This collimator reduces scatter radiation that reaches the detector array, thereby improving the image contrast and also determines the slice thickness.

In CT imaging, two collimators are used.

One collimator is mounted on the x-ray tube housing or adjacent to it.

CONTINUED

This is called Prepatient collimator that determines patient dose.

Second collimator is called predetector collimator.

THE HIGH VOLTAGE GENERATOR

All CT imaging system operate on high frequency power.

A high-frequency generator is small because the high-voltage step-up transformer is small, so it can be mounted on the rotating gantry.

Tube potential (80-140 KV).

Tube current (20-500 mA).

THE PATIENT SUPPORT COUCH

To support the patient comfortably, the patient couch must be constructed of low Z-material, such as carbon fiber.

It does not interface with x-ray beamtransmission and patient imaging.

When the patient couch positioning is not exact,the same tissue can be imaged twice , thusdoubling the dose, or it can be missed altogether.

PATIENT TABLE

The table is a flat or slightly curved platform that the patient lies on during the scan.

The table is responsible for positioning the patient with the gantry.

Up/down positioning movements are available as well as the longitudinal positioning of the patient into the gantry aperture.

POWER DISTRIBUTION UNIT

The power distribution unit is the power supply for the x–ray tube, scanning movement drive motors, table, and the detectors.

OPERATOR CONSOLE

CT imaging systems can be equipped with two or three consoles.

One consoles is used by the CT radiologic technologist to operate the imagine system.

Another console may be available for a technologist to post-process images for filming and filing.

A third console may be available for the physician to view the images and manipulate image contrast,size, and general visual appearance.

Operating ConsoleWorkstation