Charles W. Williams

An improved multicrystal 2-D BGO detector for PET

The authors evaluate and compare two 2-D array detectors for PET (positron emission tomography). Both consist of an 8*8 array of small BGO crystals coupled to a 2*2 array of photomultiplier tubes. The depth of the crystals is 3 cm in one detector and 2 cm in the other. The 2-cm detector is obviously superior in terms of material costs, but it is also superior in energy resolution per crystal, and in its ability to identify clearly the crystal containing the primary interaction. The authors present a flexible and robust algorithm for crystal identification in such array detectors. The prospect of obtaining still better spatial resolution from such block detectors, with increased numbers of crystals, is discussed.<<ETX>>

Testing 144- and 256-crystal BGO block detectors

New block detectors have been fabricated incorporating large numbers of small crystals. The authors evaluate and compare the performance of the new detectors with a standard 64-crystal block detector from Siemens-CTI. The new detectors demonstrate greatly improved imaging capability for 511 keV gamma rays. Future PET tomographs incorporating such detectors should produce substantially better volume images with little increase in tomograph manufacturing costs. The detectors will require a new type of automatic calibration procedure. Various such procedures have been tested and are discussed. A technique using higher energy gamma rays has shown special promise. >

Performance Study of the New Hamamatsu R9779 and Photonis XP20D0 Fast 2” Photomultipliers

The focus of this paper is the evaluation of the new fast 51 mm-diameter, 8-stage Hamamatsu R9779 photomultipliers (PMTs) with an acceleration-ring at the front-end and the Photonis XP20D0 PMTs with a screening grid in front of the anode. The following performance characteristics are presented: Timing resolution, anode-scan-uniformity and transit-time spread. The unfolded timing resolution for two R9779 was 192 ps and 210 ps using plastic scintillators. The individual timing resolutions for two XP20D0 using plastic scintillators are 181 ps and 154 ps, respectively. The variation in time resolution across the windows of the two R9779 ranged between 117 ps and 171 ps, and 79 ps and 73 ps for the two XP20D0 PMTs.

CURRENT AND FUTURE USE OF LSO: CE SCINTILLATORS IN PET

Single crystal scintillators of Lu2SiO5:Ce (LSO:Ce) were first developed about 15 years ago and have been in commercial use in positron emission tomography systems for more than five years. Annual ...

Comparison of typical scintillators for PET

There has been a plethora of literature describing the various properties of scintillators that are commonly used in PET detectors. In this literature there usually is a comparison made with respect to light output and energy resolution. Unfortunately, any of these comparisons are misleading because the treatment of the different scintillators is not optimized to produce the best results that may, be possible through proper surface treatment of the scintillator. In this research, there is a comparison made between the following scintillators: BGO, LSO, GSO, LYSO, and YSO. Again, the figures-of-merit for comparison were light output and energy resolution at 511 keV.