9848 Lecture Notes - Lecture 3: Ct Scan, Photostimulated Luminescence, Sagittal Plane
19 Jun 2018
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Overview of CT – lecture
Bone shows are white in ct scans
What
= Computed Tomography
The image is made up of aprox 1000+ x 1000+ of pixels in rows
Why we use CT
Does 2 major things – overcomes condensing of 3D adat into 2d image , overcome superimposition
by having 2 90degree projections , overcomes contrats resolution in planar x-ray
• Limitations of planar x-ray =
–Condensed – makes a 3D Sructuee a flat 2D image
–Superimposition (placemnt of image) of anatomical structures is a big problem with planar
radiography
• With a conventional radiograph, information with respect to the dimension parallel to the x-ray
beam is lost
• Limitations of general / planar x-ray =
– Contrast Resolution (the MOST important aspect of CT over planar x-ray)
• need 7% or more difference in attenuation in planar radiography (CR / DR) to visualise a change in
image density (ie. contrast between anatomical structures)
• CT, typically less than 0.5% attenuation difference is needed
– that is, can see more soft-tissue detail in CT than in planar x-ray
3D reconstructions
= CTA, AAA, 3D Surfaced rendered volume.
Ct axail images can be converted back to 3D images
What is Tomography
• The tomographic image is a “slice” of the patient’s anatomy
• Can be achieved in the coronal or sagittal plane (depending on pt. position) using general / planar
xray equipment with tomographic attachments
–Tube and image plate moving in opposite direction, pt. at the fulcrum
Tomography
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Document Summary
The image is made up of aprox 1000+ x 1000+ of pixels in rows. Does 2 major things overcomes condensing of 3d adat into 2d image , overcome superimposition by having 2 90degree projections , overcomes contrats resolution in planar x-ray: limitations of planar x-ray = Condensed makes a 3d sructuee a flat 2d image. Superimposition (placemnt of image) of anatomical structures is a big problem with planar radiography: with a conventional radiograph, information with respect to the dimension parallel to the x-ray beam is lost, limitations of general / planar x-ray = That is, can see more soft-tissue detail in ct than in planar x-ray. Ct axail images can be converted back to 3d images. What is tomography: the tomographic image is a slice of the patient"s anatomy, can be achieved in the coronal or sagittal plane (depending on pt. position) using general / planar xray equipment with tomographic attachments.
