Ct Module 1

Front 1

Tomography

Back 1

Method of imaging various planes of the body. Motion is used to blur certain portion of patient anatomy in order to see a particular location better.

Front 2

Planes of the body

Back 2

Human body can be shown in 3 planes. Sagittal(l and r), transverse( sup and infer) and coronal ( anter and post)

Front 3

Origin of colorful term CAT scan

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First CT scanner were only capable of reconstructing images in the transverse plane. Called computerized transaxial tomography

Front 4

Ct angiography

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Commonly used as an alternative to or in conjunction with diagnostic catheter angiography to demonstrate vascular anatomy

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Post surgical CT scan used for :

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Imaging of abdominal aortic aneurysm(AAA)

Front 6

CT roots started in what year:

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In 1917, Johann Radon developed and algorithm that reconstructed a 2 and 3D based on multiple measures if multiple locations. Meanwhile, several decades later Allan Macleod Cormack was doing some work on algorithms as well

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Geoffrey Newbol Hounsfield

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In 1967, he created the first workable unit. Americium was the rad source and took 9 days to scan and 2 hours to reconstruct

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First clinical images were acquired in what year:

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1971, head was the first part of anatomy scanned
Fact: 1979 Hounsfield won the Noble Prize for medicine and physiology

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First commercially installed CT scanners:

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In 1973

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First generation scanners

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A bag of water was placed inside the CT scanner to improve image quality. One X-ray tube and 2 detectors . Pencil beam. Head only imaging

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Second generation scanners

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Much larger X-ray beam : Fan beam. Increase in number of detectors and less overall scan time

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Third generation scanners

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Fan beam as well. Consist of a curved array of detectors. Operates continuously without stopping to translate. 360 arc of image data is obtained

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Fourth generation scanners:

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Consist of stationary array of detectors that don't rotate. The X-ray tube completes an entire 360 rotation

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Fifth generation scanners:

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They are quite different. Only Design for cardiac imaging . Use an electron beam gun

Front 15

Sixth generation scanner:

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The major change is the ability of the X-ray tube and the detectors to rotate around the patient while the pt and table move through the gantry

Front 16

Seventh generation

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Can acquire multiple sections during the scanning process. Decreases pt dose

Front 17

Dual source CT

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Second set of imaging equipment added into the scanner

Front 18

How CT scanner work:

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During the scan the X-ray tube and the detector rotate around the pt, X-rays are transmitted through recorded by detectors and converted into electrical signals. The signals are then transformed into a digital data and sent to a computer for reconstruction

Front 19

Beam geometry

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The way in which the xray beam passes through the pt and is acquired by the detectors

Front 20

Pencil beam (1st generation)

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Thin pencil beam, translate -rotate method to collect data

Front 21

Fan beam

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Introduced in 2nd generation. Shortened the scan time.fan like shape bean of about 10*

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Cone beam

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Much wider fan beam. Has about 800 detectors

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Multidetector CT

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Generally considered 3rd generation. Advantages include: faster scan time, increase anatomical coverage, thinner slices capabilities

Front 24

Two methods of data acquisition

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Sequential( slice by slice)
Spiral or helical volume acq

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Spiral of helical scanning

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An entire volume of data is acquired without the X-ray tube stopping for the pt to move to the next position

Front 26

Components of CT scanner

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1-scanning console( high quality flat panel monitor, keyboard, mouse and central processing unit, CPU)
2- gantry(X-ray tube,generators, detectors)
3-table- usually made of carbon fiber

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2 key features of gantry

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Gantry aperture and gantry tilting range

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Slip rings

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Revolutionized the design of moder CT scanners,because they eliminate the need for cables to transfer power to the gantry components and relay image data back to the computer

Front 29

2 types of filtration are used in CT

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Mathematical filter such as bone or soft tissue to change appearance of image
Beam shaping filter(bow tie filter)- change spatial distribution of the X-rays

Front 30

2 types of collimators used in CT

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Pre patient(just beyond X-ray tube) and post patient( directly below the tube collimators)

Front 31

What are detectors for?

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They pick up and measure the radiation passing through a cross section of the patient, convert those photons into electric signal and send signal to computer for processing

Front 32

The data acquisition system(DAS) has 3 functions

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1- measures rad beam that is transmitted through the patient
2-encodes these measurements into a binary data
3- finally transmits the binary data to the array processor computer

Front 33

CT is a vital role in Rad Therapy because:

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Helps to diagnose and stage cancers by evaluating size and location of tumor. Also tracks pat progress and assess Tx effectiveness(makes sense right)

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Remember the differences between a diagnostic CT scanner and CT scanner used for simulation

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Patient opening or bore is widers
Flat table top
There is an extra set of lasers that move under computer control mounted on walls

Front 35

Single photon emission computed tomography and CT

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SPECT and CT fuses physiology and anatomy . Provides true 3D data