Ch 1 Flashcards
Emission ct
Radiation source inside patient
Eg nuclear med
Transmission ct
Radiation source is outside the patient
Three steps formation of images by ct scanner
Data acquisition
Image reconstruction
Image display
Data acquisition
Collection of X-ray transmission measurements from the patient
Attenuation
Electronic detectors that measure transmission values
Scanning
Process of translate into rotate stop rotate
Volume scanning
Acquiring a volume of tissue during scanning
Image reconstruction algorithm
Computer uses special mathematical techniques to reconstruct the ct image in a finite number of steps
Ct communications
The electronic transmission of text data and images from the ct scanner to other devices such as laser printers, diagnostic workstations, display panels
Ct process
When X-ray passes through patient through the patient they are attenuated and subsequently measured by detectors. The X-ray tube and detectors are inside the gantry of the scanner and rotate around the patient . Detectors convert the X-ray photons ( attenuation date) into electrical signals or analog signals which is converted into digital signal for input into computer. The computer then performs image reconstruction. The reconstructed image into its numerical is form and is converted for tech to view.
Godfrey hounsfield and Allan cormack
Invented ct machine
First ct date?
1971
Developed first whole body ct? Year?
Robert Ledley
1974
Pg 9 generations
G
High speed ct
Created by dr Douglas Boyd
Used scan cardiovascular system without motion
Spiral/ helical ct
Aka volume scanning
X-ray tube and detectors rotate 360 while patient and table move in and out of gantry
Created by dr willi kalender
Multi slice ct scanners( Msct)
Multi detector tech that scanned four or more slices per revolution. Increases volume coverage speed
Pitch
Ratio of the distance the table travels per revolution to the nominal beam collimating
Isotropic resolution
Voxel perfect cube
Dual source ct scanner
Two X-ray tubes and two detectors specifically to image cardiac patients in short time
Three ways to reduce patient dose
- combined application to reduce dose
- ceramic detectors reduce dose by 25%
- online dose modulation , whereby the ma is optimized by to the patient characteristics to reduce dose
Acr phantom
Has four sections can be imaged simultaneously to generate several test
Ct Fluo principle
Depends on spiral helical data acquisition
Ct fluro three advances
- fast continuous scanning made possible spiral/ helical principle
- fast image reconstruction
- continuous image display by use of cine mode at frame rates of two to eight images per second
Rendering
Algorithms that help transform transaxial ct data into 3d
Rendering steps
Volume formation
Classification
Image projection
Volume visualization
Use of computer programs or visualization of tools that provide observer diagnostician with additional information from the image to facilitate diagnosis
Ct angiography
Image blood vessels opacified
Detectors two categories
Solid state detectors ( scintillation)
Gas ionization detectors ( xenon gas)
Detectors used today
Gadolinium oxysulfide, ceramic, gemstone, ultrafast ceramic
Image reconstruction
Mathematical construction of image to produce sharp, clear images of cross sectional anatomy
