Performance of prototype liquid xenon scintillation detector system for time-of-flight type positron emission tomography with improved photomultipliers

The properties of liquid Xe are considered to be advantageous for application to time-of-flight positron emission tomography (TOF-PET). Previously, we constructed a prototype liquid Xe TOF-PET detector using photomultiplier tubes (PMTs), which can operate at liquid xenon temperature, and investigated their performance. Their poor quantum efficiency and low gain, however, were not sufficient for use in TOF-PET. Recently, new PMTs with five times higher quantum efficiency in liquid Xe and ten times higher gain than the previous PMTs have been developed by Hamamatsu Photonics Co. The prototype PET detectors, presented here, were constructed using these new PMTs and tested. An energy resolution of 15.9% (FWHM), a position resolution of 2.1-3.5 mm (FWHM), and a timing resolution of 260 ps (FWHM) were achieved.