COMPUTER TOMOGRAPHY

BY -: Lovnish Thakur (IBT -1ST Semester)Enrollment N o. -: ASU2014010100099From -: school of bioscience

Computer tomography (CT), originally known as computed axial tomography (CAT or CT scan) and body section

rentenography.

It is a medical imaging method employing tomography wheredigital geometry processing is used to generate a three-dimensional image of the internals of an object from a largeseries of two-dimensional X-ray images taken around a singleaxis of rotation.

The word "tomography" is derived from the Greek tomos (slice)and graphein (to write). CT produces a volume of data whichcan be manipulated, through a process known as windowing, inorder to demonstrate various structures based on their ability toblock the X-ray beam.

CT: The beginning

CT founded in 1970 by Sir Godfrey Hounsfield

first applications were in neuroradiology.

CT Scanner

Used to determine

extent of trauma

location and type

of tumors

status of blood

vessels

-pre surgical planning

Basic CT scanner components

Gantry

X-Ray Tube

Detector

Control Console

Gantry. The CT scanner gantry is a moveable frame that

contains the x-ray tube, including: collimators and filters, detectors, data acquisition system, rotational components including slip ring systems, and all associated

electronics such as

CT scanner gantry

angulation motors

& positioning laser

lights.

Capture energy that has not been attenuatedby the patient.

Digital projection

AP, PA, Lat or Oblique projection

Conventional CT

-Axial

Volumetric CT

- Helical or spiral CT

X-ray tube and detectorremain stationary

Patient table movescontinuously

Produces an imagecovering a range ofanatomy

Image used todetermine scan location

Digital Projection

Axial CT X-ray tube and detector rotate 360°

Patient table is stationary

Produces one cross-sectional image

Once this is complete patient is moved to next position.

X-ray tube and detector rotate 360°

Patient table moves continuously

Produces a helix of image information

Attenuation

X-ray beam passes through patient

Each structure attenuates X-ray beam differently

According to individual densities

Radiation received by detector varies according to these densities

Transferred from detector to CT computer(A to D converter)

Reconstructed by computer into a cross-sectional imageDisplayed on screen

Each pixel displayed on monitor has varying brightnessThe greater the attenuation, the brighter the pixel

The less attenuation, the darker the pixel

Density values correspond to

a range of numbers

Hounsfield scale

Density information

Window widthDetermines range of CT numbers displayed on animage

-:Values above this range = white

-:Values below this range = blackWindow level

Sets the center CT number displayed on themonitor

CT image quality

Spatial resolution Ability to resolve small objects in an image.

Contrast resolution Ability to differentiate small density differences in an

image.

Post Processing Options• Visualization of vasculature in relation to pathology.• Show course of vessels.• Define vascular stricture.

CT SCANNERThus provide a window into the

body.

SOME OF IMAGE FORMED BY CT SCAN

THANK YOU