CT EQUIPMENTATION

1. CT EQUIPMENTATION
- Ms. Geetashree Majumdar
Assist. Professor
Department of Radiology &
Imaging technology

3. Principle of CT
•cross sectional images can be obtained from
multiple projection.
•When patient is exposed by the x rays, Those
data carrying x rays will be received by the
detectors .
•Then detectors convert these x ray photon
into electrical signal.

6. CT instrumentation
Three major system are present-
• The imaging system/ gantry
• The computer
• The display, recording and storage system

7. Purpose of imaging
system/gantry
• To produce x rays
• Shape and filter the x ray beam to pass through a
defined section.
• To convert the transmitted photons into digital
signal.

9. Major components of imaging
system/ gantry
• X- ray tube and generator
• Pre- collimator
• Filter
• Post collimator
• Detector
• Slip ring device
• Data acquisition system
• Cooling system

11. X RAY TUBE
• Rotating anode x ray tube.
• Diameter of anode is 5 inch.
• Focal spot size is 0.6mm
• Small target angle-12degree
• Rotation speed of anode is 3600-10000rpm.
• Anode- rhenium, tungsten, molybdenum.

12. GENERATOR
• High voltage generator, 5-50khz.
• Power rating range is 30-60kw
• Generator produces high voltage and transmit it to
the x ray tube.
• CT scanner now use high frequency generator
which are small in size.
• It is mounted close to the x ray tube.

13. COLLIMATOR
•Define thickness.
•Reduces patient dose.
•Improve image quality.
•There are two types of collimator- pre collimator
and post collimator.
•Pre collimator is mounted on the x ray tube housing
which determine patient dose.
•Post collimator located in front of the detectors to
protect them from scattered radition.

14. DETECTORS
• Capture radiation beam from patient and
convert them into electrical signal and
digital signal.
• Transmit the digital signal to computer
system for further processing.
• Two types of detectors are used-
scintillation detector and gas ionization
detector.

15. DAS( DATAACQUISITION
SYSTEM)
• Amplifier- signal from the detectors goes to
amplifierfor signal magnificationand then sent to
sample hold. Sample hold is located between the
amplifier and ADC.
• ADC- ( analog to digital converter) . Converts
analog signal to digital signal. Devides the
electrical signal into multiple parts and measured
in bits. Modern CT Scanner Use 16bits ADC.

16. SLIP RING DEVICE
• Electromechanical devices consisting of
circular electrical conductive rings and
brushes .
• Prior to the introduction of of slip ring,
only axial scanning was possible which
had need to stop.
• It reduces patient motion.
• Eliminates inter scan delay.

18. COOLING SYSTEM
• Cooling mechanisms are included in the gantry.
They can take different forms, such as blowers,
filters, or devices that perform oil to air heat
exchange.
• Cooling mechanisms are important because
many components can be affected by
temperature fluctuations.

19. COMPUTER SYSTEM
• Receives digital
signal from DAS and
process to reconstruct
an image of cross
sectional anatomy.
• Large storage
capacity, fast and
efficient processing.
• Composed of
hardware and
software..
• Software helping CT
user to communicate
with CT system eg:
modify protocols,
parameter etc.

20. PATIENT TABLE
• Couch top is made up of carbon fiber.
• It is a platform for the patient to lie down
during the examination.

21. DISPLAY
• Display ouput image.
• Provides permanent hard copy.

22. RECORDING STORAGE
• magnetic disc.
• Magnetic tap.
• Digital videotap.
• Optical disc.
• Optical tap.