Collimator design and manufacturing for a mobile tomographic gamma camera system based on ectomography

Tomographic scintigraphy such as conventional single photon emission tomography (SPECT), ectomography, fan and cone beam SPECT require high quality collimators to avoid image artifacts and to achieve designs differing from the standard parallel hole collimator. Ectomography is a tomographic method implemented as a mobile system. Improvements in the performance of a mobile gamma camera system based on ectomography can be obtained with segmented collimators. The sensitivity of the gamma camera system is increased with a factor equal to the number of segments of the collimator compared to an non-segmented collimator. This makes it possible to reduce acquisition time or reduce radiation dose to the patient without degrading image quality. Comparison with patient myocardial perfusion data gives that it would, in most cases, be possible to use a slant angle of 40° and a segmentation of the collimator into 4 segments. However, the present manufacturing technology limits the maximum slant angle to approximately 30° and therefore a new manufacturing technique for collimators has been developed. A mould for casting is produced by making slits by wire electrical discharge machining. Accuracy, resolution and sensitivity of such a small scale collimator prototype is higher than or equivalent to a conventional cast collimator. The proposed method is found to be especially suitable for producing complex collimators. Since the new proposed technique results in better accuracy of the final collimator than conventional manufacturing methods does, it holds a promise to less artifacts in nuclear imaging, such as in ectomography and SPECT