Talk:Gamma camera
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The best current camera system designs can differentiate two separate point sources of gamma photons located a minimum of 1.8 cm apart, at 5 cm away from the camera face. - 1.8cm seems pretty poor? Is it interpolated in some way to get a better resolution? or is this a typo?
A: I'm afraid that this is not a typo, and no we do not in general interpolate images to improve resolution (at least not at the digital image level - a certain amount of interpolation occurs when displaying or printing the images). Remember that Nuclear Medicine is not used for anatomical imaging, so resolution is not as important as you might expect. If we need to locate a physical mass then a CT or MRI can be used. If on the other hand you want to know how well an organ is functioning then Nuclear Medicine images can be used to answer this question (even with poor resolution). [Think of how much we can tell about organ function from a blood test which has no image information at all]
Collimation can be acheived without use of pin holes and large collimators. Consider compton scattering interactions in which the photon is incident and scaterred through an angle with a resulting energy related to the scattering angle. Placing a thin 'pixelated' semiconductor detector before a main 'pixelated' semiconductor detecor will act as a scattering medium before the main detector. Thus, both interactions are well resolved in energy and space and the compton scattering formula can be used to project a cone into the patient plane in which the orignal photon emission occured. By continuted projection and interception of many cones the source can be well defined in 3d space, with millimeter resolution (the limit of resolution is related to the recoil momentum of the electron ~ 0.6mm @ 551keV). This method also has the advantage of using nearly all emitted photons. The technique is being developed for medical imaging (PET and SPECT) with germanium detectors and security screening using CZT due to the temperature of operation.
