Evaluation of renal function, using a scintillation camera and computer.

Abstract

SIGMAN, BENDER, and Blau (1) have described the use of the autofluoroscope in radioHippuran renography. The uptake and clearance of 1311 Hippuran in various subdivisions of the kidney (cortex, medulla, and pelvis) were plotted. These compartmental renograms aided the investigators in the interpretation of various abnormalitie s seen on the reno gram pattern of the whole kidney. A scintillation camera has been used by Burke and his associates for evaluat ion of ren al function (2- 4). Their method combines good detection efficiency and accurate organ localization with graphic recording of the uptake and clearance of the radioisotope by each kidney. The serial camera images are particularly useful in sorting out the similar renogram patternsof parench ymal disease, renal artery stenosis, and obstruction (2). In the present study we extended scintillation camera and compartmental renography to include computer analysis and print-out of th e data. The valu e of this technic in the assessment of a varie ty of renal diseases is illustrated. Materials and Methods The equipment shown in schemat ic form in Figure 1 consists of a modified scintillation camera with elect ronic splitting of the crystal, analog-to-digital computer, 1,600channel memory system, and high-speed magn etic tape for computer proce ssing. The 1,600 chann els represent a 40 X 40 grid with each channel recording the acti vity from approximately one-half square centimeter of surface area. The data are accumulated in the 1,600 channel memory system and are transferred to magnetic tape at preset time intervals. A FORTRAN program has been written to analyze the tape data on a Control Data Corporation 3300 computer. All patients were given nothing by mouth for twelve hours prior to study. With the patient in a sitting position and use of a kidney, ureter, and bladder study or intravenous urogram as a guide, the camera was directed toward the kidneys from the back. Immediately upon injection of a bolus of 200-500 )lCi of 1311Hippuran intravenously, the scaler, rectilinear chart recorders, and the 1,600-channel memory system with magnetic tape were activated. The data were cleared from the 1,600-word memory onto the tape at O.4-min. intervals. Serial camera images were routinely obtained at approximately one, three, six, twelve, eighteen, twenty-four, and thirty minutes. Additional camera images were taken at later times in selected patients. Following the study, the data were played back from the magnetic tape unit into the 1,600-memory system and displayed on an oscilloscope where the appropriate x-y coordinates of regions of interest (ROI) were selected. The accuracy in the selection of ROI on the oscilloscope was verified at a later time by comparison to the isointensity plot obtained from the computer (Fig. 2). If errors were present in the original ROI selections, appropriate changes were made and the computer reprogrammed.