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23 Cards in this Set
- Front
- Back
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What are some examples of variable factors in SPECT?
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time of acquisition
projections per rotation total degrees of rotation matrix size computer memory space radius of rotation collimator |
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The physical size of a pixel is found by q
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FOV/n
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To mathematically arrive at the matrix size which takes full advantage of a camera systems resolution.......
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FWHM/3
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In general, the more projections obtained....
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the better the final reconstructed image in SPECT
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If we increase the number of projections......
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we must increase the acquisition time or dose in order to get enough data to be useful.
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SPECT studies with fewer than 60 projections
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have poor quality.
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However, increasing the number of projections up to a point also has no effect.
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For example, obtaining 128 projections instead of 64....... will not gi beve any significant improvement in picture quality.
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The number of projections must be greater
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than or equal to the matrix size,
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Streak Artifacts
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can be produced if the number of projections fall below the matrix size
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The total counts in a SPECT study range from
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2-8 million counts
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Radius of Rotation
Probably the biggest disadvantages of SPECT....... |
poor resolution
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Poor Resolution is due to
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the detector distance which has to travel a 360 degrees orbit around the patient.
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Radius of Rotation
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The only point during acquisition in the patient which remains the same distance from the camera is the center of rotation.
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The center is therefore.....
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the only point where with constant and symmetric resolution. This can lead to distortion in the reconstructed images.
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The total counts in a SPECT study range from
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2-8 million counts
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Radius of Rotation
Probably the biggest disadvantages of SPECT....... |
poor resolution
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Poor Resolution is due to
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the detector distance which has to travel a 360 degrees orbit around the patient.
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Radius of Rotation
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The only point during acquisition in the patient which remains the same distance from the camera is the center of rotation.
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The center is therefore.....
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the only point where with constant and symmetric resolution. This can lead to distortion in the reconstructed images.
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An increase in the collimator length will
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decrease scatter.....decrease sensitivity....and in increase resolution
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An increase in collimator hole diameter will
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increase sensitivity......increase scatter, and decrease resolution
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A decrease in collimator hole diameter will
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increase the # of holes ( smaller holes closer together)......increase resolution and decrease sensitivity.
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A increase in septal thickness such as in a medium or high energy collimator will
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decrease scatter.......decrease sensitivity...... and may decrease resolution
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