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A multislice fan beam collimator was designed for a SPECT system with a rotating scintillation camera, and it was constructed by the lead casting method which was devised in recent years. The focal length from the surface of the detector side of the collimator is 75 cm. In order to reconstruct the SPECT images we modified the interpolation method which was developed for reconstruction of the X-ray CT and applied it. Primary photopeak data were obtained with a 20% energy window centered at 140 keV for 99mTc and 159 keV for 123I. The fan beam collimator reduces the field of view, and it would therefore be limited to use only for the head and neck region at present; however, both resolution and sensitivity were approximately 20% better than those of the parallel hole collimator. A fan beam collimator is a useful implement for the SPECT study.

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We detected a regional defect in the pons with ipsilateral cerebellar hypoperfusion in a patient with acoustic neuroma by brain SPECT with 99mTc HMPAO. A high spatial resolution SPECT system with three detectors equipped with fan-beam collimators was employed. This is the first report of a defect in the brainstem being visualized by perfusion SPECT and this method could make it possible to clarify the cause of a remote effect on the cerebellar perfusion by injury to the brainstem.

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