SPECT imaging of iodine-131 distribution in the head

The performance of a pinhole collimator for I-131 SPECT of the head was evaluated. The evaluation included planar and SPECT spatial resolution, sensitivity in air and in water, reconstructed image quality, and activity quantitation within a simple phantom that models tumor uptake in the head. The pinhole collimator was compared to medium and high energy parallel hole collimators. The pinhole collimator showed improved resolution/sensitivity trade-off compared with the parallel hole collimators over the range of distances relevant to head imaging. Penetration artifacts were not apparent in the reconstructed pinhole images. The accuracy of activity quantitation with the pinhole and parallel hole collimators was dependent on the segmentation threshold and calibration procedure. These results indicate that pinhole collimation can provide improved performance over conventional parallel hole collimators for I-131 imaging in the head.