A NONIMAGING SCINTILLATION PROBE TO MEASURE PENILE HEMODYNAMICS

We have developed a penile nonimaging scintillation (PNIS) probe consi sting of a plastic well-type scintillation crystal interfaced to a por table computer and acquisition board. This report describes the design of the PNIS probe, performance characteristics, mode of usage and ill ustrative results which demonstrate its capabilities. Methods: With th e PNIS probe, penile blood-pool studies were performed in nine patient s utilizing 3.7 MBq (100 mu Ci) autologous Tc-99m-labeled red blood ce lls (RBCs). Venous blood standards were assayed to enable conversion o f the count rate to volummetric measurements. Washin of peripherally a dministered Tc-99m-RBCs was mathematically analyzed to estimate penile blood volume and cavernosal flow rate in the flaccid state. The rate of change of penile blood volume after intracavernosal vasodilators wa s used to generate measures of stimulated flow. Results: A major advan tage of this device over the gamma-camera is a 3300-fold increase in c ount rate sensitivity, which allows for markedly improved temporal res olution while significantly reducing the radiopharmaceutical dosage. A dditionally, the PNIS probe is portable, economical and is not depende nt on operator-defined regions of interest. Count rate sensitivity is relatively constant within the bore, with the exception of the proxima l region adjacent to the opening, where geometric efficiency is reduce d. Conclusion: The PNIS probe is an effective device for measuring pen ile activity in radionuclide studies, allowing for acquisition of time -activity curves of the penis during flaccid washin of peripherally la beled red blood cells and after pharmacologic stimulation to induce er ection.