Week 1 - Intro To CT Flashcards
Process of producing an image of a 2 dimensional distribution from estimates of its line integrals along finite number of lines of known locations
Image reconstruction
Reformatting into a different plane
MPR
Multi planar reformatting
Greek for cutting/section
Tomos
Researchers were attempting to acquire “body section radiography”
1920s
Grossman refined the technique and labeled it tomography
1935
Preliminary image
Lateral and AP
Topogram, scout, scanogram
Continuous acquisition scanning
Spiral, helical, isotropic
Done before any scan to figure out anatomy, done AP and lateral, also done to ensure Isocentering
Scout, scanogram, topogram
What are some differences between CT and radiography?
CT images show cross sectional anatomy
CT produces 3D images that are computer generated with use of transaxial dataset
Changing from 2D to 3D
Reconstructing
Changing from one plane to another
Reformatting
T/F
Radiography can not distinguish between tissues with <10% tissue contrast
True
What is the goal of CT?
-minimize superimposition
-improve image contrast
-record small differences in tissue contrast
Determined the thickness of the slice
Z axis
Determined by use of collimators
Indicates width of slice
X
Indicated height of slice
Y
Adding what to X and Y make it a voxel?
Z
What are some limitations of CT?
Poorer spatial resolution
Higher dose
Beam hardening artifacts
Streak artifacts
What is temporal resolution particularity important for?
Cardiac imaging
A horizontal plane that passes through the body, dividing it into superior and inferior portions
Axial / transverse
*all CT images are acquired in axial
A vertical plane that passes through the body, dividing it into right and left portions
Sagittal
A vertical plane that passes through the body, dividing it into anterior and posterior portions
Coronal
A plane that passes diagonally between axes of two other planes
Oblique
Formation of CT images involves 3 steps:
-data acquisition
-image reconstruction
-image display
Collection of xray transmission measurements from the patient
Quantitative
Detector moves around the patient at a particular section. Table then moves and the detector moves around the patient again
Axial
Xray tube and detectors continuously rotate as the patient moves through the scanner simultaneously
Helical
Radiation passes through sections of the body and sends signals to CPU from the detectors
Image reconstruction
First CT developed
1971
20 minutes per image
First patient was scanned
1972
What is a benefit of a dual source CT?
Excellent spatial and temporal resolution
Acquiring a volume of tissue during the scanning
Volume scanning
Artifacts that result from preferential absorption of the low energy photons, which leaves high intensity photons to strike the detector array
Beam hardening artifacts
What materials can be used for filtering?
Teflon or aluminum
