Development of a Small Gamma Camera Using NaI ( T1 ) - Position Sensitive Photomultiplier Tube for Breast Imaging

Kim, Jong Ho; Choi, Yong; Kwon, Hong Seong; Kim, Hee Joung; Kim, Sang Eun; Choe, Yearn Seong; Lee, Kyung Han; Kim, Moon Hae; Joo, Koan Sik; Kim, Byung Tae

Abstract

PURPOSE: The conventional gamma camera is not ideal for scintimammography because of its large detector size ( 500 mm in width) causing high cost and low image quality. We are developing a small gamma camera dedicated for breast imaging.
MATERIALS AND METHODS
The small gamma camera system consists of a NaI (Tl) crystal (60 mm X60 mm X6 mm) coupled with a Hamamatsu R3941 Position Sensitive Photomultiplier Tube (PSPMT), a resister chain circuit, preamplifiers, nuclear instrument modules, an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a standard resistive charge division which multiplexes the 34 cross wire anode channels into 4 signals (X, X, Y, Y ). Those signals were individually amplified by four preamplifers and then, shaped and amplified by amplifiers. The signals were discriminated and digitized via triggering signal and used to localize the position of an event by applying the Anger logic.
RESULTS
The intrinsic sensitivity of the system was approximately 8,000 counts/.'ec/pCi. High quality flood and hole mask images were obtained. Breast phantom containing 2-7 mm diameter spheres was successfully imaged with a parallel hole collimator. The image displayed accurate size and activity distribution over the imaging field of view.
CONCLUSION
We have succesfully developed a small gamma camera using NaI(T1)-PSPMT and nuclear instrument modules. The small gamma camera developed in this study might imprnve the diagnostic accuracy of scintimammography by optimally imaging the breast.