Development of a positron-imaging detector with background rejection capability.
OBJECTIVE
Intra-operative probes have recently become important instruments in nuclear medicine. In such an application, the radiopharmaceutical F-18-fluorodeoxyglucose (FDG) is promising. For the FDG-guided surgery, we developed and tested a positron-imaging detector with background rejection capability.


METHODS
The detector consists of an array of phoswich scintillators, a multi-channel position-sensitive photo-multiplier tube (PSPMT) and an electronic circuit. The scintillators and the PSPMT are encased in a tungsten shield and replaceable collimators are mounted on the top of the detector. Positrons are detected by the plastic scintillators while annihilation photons are detected by the BGOs. By employing a pulse-shape analysis, we can distinguish the true events (positrons) from background gamma events. The dimensions of each plastic scintillator are 2 mm x 2 mm x 3 mm and those of the BGO are 2 mm x 2 mm x 15 mm. These scintillators are optically coupled to each other and combined in an 8 x 8 array, which is optically coupled to a 1-inch square 8 x 8 multi-channel PSPMT via optical fibers. Position determination of the positrons is performed by 64-channel threshold circuits while the pulse shape analysis is applied for the summing signal.


RESULTS
The spatial resolution was measured by positioning an F-18 point source onto one pixel of the detector and found than the spillover to the neighbor pixel was less than 20%. The background count rate was less than 2 cps for a 20-cm diameter, 20-cm long cylinder phantom containing 3.7 MBq of F-18.


CONCLUSIONS
These results indicated that the developed positron-imaging detector will be useful for FDG-guided surgery.
Yamamoto
Seiichi
S
Department of Electrical Engineering, Kobe City College of Technology, 8-3 Gakuen-Higashi-machi, Nishi-ku, Kobe 651-2194, Japan. s-yama@kobe-kosen.ac.jp
Higashi
Tatsuya
T
Matsumoto
Keiichi
K
Senda
Michio
M
D016477:Artifacts; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D008904:Miniaturization; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D014159:Transducers