Pinhole SPECT can generate sectional nuclear images of a normal and morbid ankle and hindfoot with remarkably enhanced resolution by portraying the topography and pathological alterations in great detail.
Methods: Pinhole SPECT was performed using a commercially available single-head, rotating gamma camera system by replacing the parallel-hole collimator used for planar SPECT with a pinhole collimator. The images were reconstructed in the same way as in planar SPECT by using the filtered back-projection algorithm and a Butterworth filter. First, we compared the scan resolution between the planar and pinhole SPECT images of a thyroid phantom and a normal ankle and hindfoot by working out pinhole SPECT anatomy with CT validation. Second, the clinical usefulness was assessed in one case each of fracture, reflex sympathetic dystrophy syndrome and rheumatoid arthritis of the ankle with radiographic correlation. The resolution of the pinhole SPECT and planar pinhole images was compared for these diseases.
Results: The resolution of the pinhole SPECT of a thyroid phantom and of a normal ankle and hindfoot was significantly enhanced compared to the planar SPECT although image distortion was seen in the periphery of the field-of-view. The pinhole SPECT resolution was such that most of the anatomical landmarks were sharply delineated in the ankle and hindfoot and some useful diagnostic signs in the diseased ankle were visible.
Conclusion: Pinhole SPECT can be performed using a single-head gamma camera system and filtered back-projection algorithm. It generates sectional scan images of both normal and morbid ankle and hindfoot with enhanced resolution portraying many anatomical landmarks and pathological signs in useful detail.