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14 Cards in this Set
- Front
- Back
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Adv of slip ring |
Faster axial scanning Helical scanning possible Cine scanning CT fluoroscopy |
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MDCT |
Multiple detector rows Each has narrow width in which x-rays are detected on scintillation crystals |
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Benefits of helical scanning |
Minimise motion artifacts Reduces patient dose Improves spacial resolution in z-axis Enhanced multiplanar or 3D rendering |
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Back Projection |
Blurry images Reverse process of measurement of projection data to reconstruct image Each projection is smeared back across the reconstructed image |
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Filtered back projection |
Filtered prior to reconstruction Different filters for different examinations, smooth for soft and sharp for his resolution |
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Iterative reconstruction |
All matric points assumed to have same value. Values compared with measured values, corrections made to bring them into agreement, process repeated until assumed and measured values are the same or within tolerance. |
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3 types of iterative reconstruction |
Simultaneous Ray by ray Point by point |
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Simultaneous reconstruction |
All p4ojec5ions from matrix calculated at beginning of iteration. Corrections made simultaneously for each iteration |
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Ray by ray correction |
One ray sum calculated and corrected, corrections incorporated in to future ray sums |
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Point by point correction |
Calculations and corrections made for all Ray's passing through one point, used in ensuring calculations. Process repeated for every point. |
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Window Level |
CT number of mid grey. Average HU of interested tissues |
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Window Width |
Number of HU from black to white. Spread of HU required |
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Disadvantages of CT |
Ionising radiation Potential nephrotoxicity from iodinated contrast agents Inability to differentiate between residual tumour or fibrosis and a reoccurrence after treatment Sometimes difficult to visualise tumour or anatomy Metsl implants can produce artifacts |
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MDCT advantages |
Wider coverage Shorter scan times Reduced radiation exposure Reduced contrast requirements |
