The scintillation camera with diverging collimator: Physical parameters and a clinical evaluation

The Pho/Gamma III with diverging collimator was compared to two dual-headed scanners. Both physical parameters and clinical scans were studied. Diverging collimator resolution was measured by the modulation transfer function (MIT) computed from a line-spread function obtained with a 1600-channel analyzer. Analysis of MTF data showed that there is no significant septal penetration at 390 IceV, and that the resolution is quite comparable to the MTF of a 3-inch rectilinear scanner with 19-hole 3-inch focused collimator. Thirty patients had lung scans with 113min on both a scintillation camera with diverging collimator, and a dual 3-inch Picker rectilinear scanner with 19-hole collimator (2107). On the average, the examination time with this nuclide (patient positioning plus exposure) was about the same with each technique. In no instance was a lesion detected with one system and not detected with the other. The studies were identical in 23 cases. In four instances the scanner was better, in three instances the camera was better. A second series of eight patients was compared using a dual 5-inch Ohio-Nuclear (84D) with 38H-collimators, and the Pho/Gamma III with diverging collimator. The nuclide in this series was SSmTc-labeled1 albumin microspheres. An appreciable resolution loss was noted on the “up” side view with the scanner especially with the patient supine. This is believed due to increased respiratory motion and inability to place the detector near the chest wall especially over the apices. The images from the two systems were otherwise comparable. The total examination time was much shorter with the camera and this nuclide, taking one-third to one-half the time necessary with the dual 5-inch scanner. The diverging collimator is a valuable accessory to the gamma camera. It provides an increase in the useful field of view (13 inches in diameter, at a distance of 4 inches from the collimator face) with satisfactory resolution and adequate sensitivity.