A zyxw Miniature Gamma Camera' J. zyxwvutsr N. AARSVOLD,~ R. A. MINTZER,~ N. J. YASILLO,~ S. J. HEIMSATH; T. A. BLOCK: K. L. MATTHEWS,b X. PAN: C. WU,b R. N. BECK! C-T. CHEN,b bFrank Center for Image Analysis Franklin McLean Memorial Research Institute Department of zyxwv Radiology CDepartmentof Surgery University of Chicago Chicago, Illinois 60637 AND M. zyxwv COOPER^ INTRODUCTION Radiotracer imaging procedures, such as planar nuclear medicine scans and single-photon emission computed tomography (SPECT) studies, are useful compo- nents of diagnostic and treatment-assessment protocols applied to patients who have sustained high-voltage electrical injuries.'-'* However, such imaging procedures are often difficult to perform because they usually require transport of patients to nuclear medicine clinics. We have designed and constructed a prototype mobile miniature-gamma-camera system that can be used in electrical trauma units. In this paper, we discuss the design of the prototype and report the present imaging characteristics of this system. GAMMA-CAMERA IMAGING Most gamma cameras have four major components: a scintillation crystal [NaI(Tl)], an array of photomultiplier tubes (PMTs), a parallel-hole collimator (lead), and radiation shielding (lead). They produce images as follows: The radiation shielding and collimator septa stop gamma rays directed at the camera, except those that pass through the collimator holes. The gamma rays that pass through the holes are photons traveling essentially parallel to the sides of the holes and perpendicular to the front face of the scintillation crystal. Although some of the gamma rays that reach the scintillation crystal pass through the crystal undetected, most interact with the crystal and are converted to light. The light is detected by the PMTs and converted to electrical signals. All of the PMTs in the array detect some light. However, the amount of light detected by each tube, and thus the magnitude of the signal that each produces, differs. In other words, each PMT response depends on "Support for this work was provided by the Department of Energy through Grant No. DE-FG02-86ER60418 and by the Electrical Power Research Institute. 192