Potential artifacts associated with the scanning pattern of the EMI scanner.

Physical and geometrical considerations of the EMI scanner are used to predict that regions of the head can be missed by adopting a scanner procedure based on the nominal EMI slice thickness. Using a nominal slice thickness of 1.3 cm and effective focal spot length of 12 mm, one can predict that in the central portion of the head, up to 8% of the region scanned may not be imaged. Moreover, it is shown that simultaneous monitoring of a single focal spot by two adjacent detectors, as in the EMI system, would lead to significant overlap between the two adjacent EMI slices resulting in dual imaging. Experimental examples are shown to illustrate these two artifacts in the EMI scanner.