PSPMT AND PHOTODIODE DESIGNS OF A SMALL SCINTILLATION CAMERA FOR IMAGING MALIGNANT BREAST-TUMORS

We are investigating the concept of utilizing a small gamma ray scinti llation camera to help identify and localize malignant breast tumors a fter a suspicious finding in a mammogram. Excellent sensitivity and sp ecificity for malignant breast tumors has been achieved using conventi onal nuclear medicine scintillation cameras with certain Tc-99m labele d radiopharmaceuticals. However, because of the large size, low image resolution and high cost of these devices, they are not ideal for use in breast imaging in a mammography suite. A dedicated miniaturized cam era would allow imaging at angles that are physically impossible with the standard camera. These lateral views would not include the backgro und activity from the heart and liver. In addition, with a potentially higher intrinsic resolution, shorter collimator and if breast compres sion is applied, a small camera could significantly improve the sensit ivity and signal to noise ratio for the scintillation imaging method. We are exploring two different photodetector technologies for a small prototype camera development. The first uses a position sensitive phot omultiplier (PSPMT) as the photodetector, the second, an array of sili con PIN photodiodes (PD). In this report, we present imaging results o btained with a NaI(Tl)-PSPMT design, and the design features, expected performance and relevant energy and position measurements obtained fo r a test CsI(Tl)-PD device.