4. system components

System Components
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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Lecturer in Medical Imaging
Medical Imaging Technologist (MIT) - Radiology
Master in Public Health (MPH)
Email: RFafridi@hotmail.com

Main Components of CT
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CT
Scanner
Gantry Data Acquisition
System
Operating
Console

System Components
• Basic system components of
a modern third-generation CT
system.
• Third-generation CT scanners
use the so-called rotate–
rotate geometry, in which
both the X-ray tube and the
detector rotate about the
patient.
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System Components
• The overall performance of a CT system depends on several key
components.
• These components include the X-ray source, a high-powered
generator, detector, data transmission systems, and the
computer system for image reconstruction and manipulation.
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Gantry
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High Voltage
Generator X-ray tube
Pre Patient
Collimator Patient
Post Patient
Collimator Detector
X ray source
Pre Patient Collimation
Post Patient
Collimation
X-ray Detector
Gantry
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• Two types of detectors are used
• Scintillation Detectors
• Gas Filled Detectors
• Scintillation Detectors
• Materials Used
• Sodium Iodide
• Bismuth Germanium Oxide
• Cesium Iodide
• Cadmium Tungstate Scintillator
Crystal
Photo Multiplier
Detector
Rings
Detectors
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Gas Filled Detectors
• Materials Used
• Xenon
• Krypton
• Xenon + Krypton
Since 90% of 50 is 45, the output is same. The overall efficiency of both the
detectors is same.
Gas Filled Detectors Scintillation Detectors
Sensitive face: 100%
Detection Efficiency: 45%
Sensitive face: 50%
Detection Efficiency: 90%
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Slip-Ring Technology
• Slip rings eliminate the need for cables
making possible continuous rotation
resulting in multislice helical CT.
• Slip rings are electromechanical devices
that conduct electricity and electrical
signals through rings and brushes from a
rotating surface onto a fixed surface.
• Helical CT is made possible by the use of
slip-ring technology, which allows the
gantry to rotate continuously without
interruption.
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Slip rings and brushes electrically connect the
components on the rotating gantry with the rest of
the multislice helical computed tomography
imaging system.

• The DAS consists of the following parts
• X-ray photons come on the detector.
• The detector detects the intensity in form of current.
• The current is converted into voltage.
• The analog integrator removes spikes.
• The analog signal is converted into digital form.
• This signal can now be processed and reconstructed in the computer.
Detector
Current to
Voltage
Convertor
Pre
Amplifier
Analog
Integrator
Analog to
Digital
Convertor
Computer
Data Acquisition System
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Image Reconstruction
• After enough transmission measurements (detector)
• Sent to the computer for processing
• A software called Fourier Slice Transform is used.
• More than 250,000 reconstruction algorithms are used
(example: algebraic reconstruction technique) to compute the
image.
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• The operating console is the master control center of the
CATscanner
• It is used to input all of the factors related to taking a
scan.
• Typically, this console is made up of a computer, a
keyboard, and multiple monitors.
• Often there are two different control consoles, one used
by the CAT scanner operator, and the other used by the
physician.
• The operator's console controls such variables as the
thickness of the imaged tissue slice, mechanical
movement of the patient couch, and other radiographic
technique factors.
Operating Console
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• End of the lecture
• Thank you!
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4. system components

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