Question

how is the collimator used in SPECT different than the one used in PET? and how is reconstruction different between both of them?

Answer 1

Spect Collimators

In spect, a number of approaches were investigated to increase senstivity through optimal design of the collimator. One approach is to use shorter collimators in order to reject a smaller portion of incident events. However,this approach degrades the resolution of the camera.

PET Collimators

Due to the nature of positron anhillation in which two opposite anhillation photons are emmitted from same event, physical collimators can be entirely removed in PET, with the collimation instead perform electronically using the coincidence detection method. This implies a much larger angle of acceptence at each detector position, Resulting in the order of nearly 1% of emitted events being detected in PET.

There are many important implications to this significant gain in senstivity for PET;

1. Improved image quality
2. Posibility of performing shorter scans.
3. Multiple field of view scanning.
4. Improved temporal resolution.