Andrew G. Weisenberger

Performance Evaluation of a Dedicated Camera Suitable for Dynamic Radiopharmaceuticals Evaluation in Small Animals

As the result of a collaboration between the Detector and Imaging Group of Thomas Jefferson National Accelerator Facility (US), the Institute of Radioisotopes and Radiodiagnostic Products (IRRP) of N.C.S.R. ldquoDemokritosrdquo and the Biomedical Simulations and Imaging Applications Laboratory (BIOSIM) of National Technical University of Athens (Greece), a mouse sized camera optimized for Tc99m imaging was developed. The detector was built in Jefferson Lab and transferred to Greece, where it was evaluated with phantoms and small animals. The system will be used initially for planar dynamic studies in small animals, in order to assess the performance of new radiolabeled biomolecules for oncological studies. The active area of the detector is approximately 48 mm times 96 mm. It is based on two flat-panel Hamamatsu H8500 position sensitive photomultiplier tubes (PSPMT), a pixelated NaI(Tl) scintillator and a high resolution lead parallel-hole collimator. The system was developed to optimize both sensitivity and resolution for in vivo imaging of small animals injected with technetium compounds. The results of system evaluation in planar mode with phantoms are reported. Results are presented for in vivo dynamic studies of mice injected with > 100 muCi of two conventional and novel radiopharmaceuticals, namely Tc99m-MDP and Tc99m -Bombesin.

Embedded waveshifting fiber readout of long scintillators

A method was tested for reading out light from long scintillators by embedding, waveshifting fibers in longitudinal grooves made in the scintillators which are then connected to a photomultiplier (PM). With PMs on both ends of the fibers, attenuation lengths of over 5 m and light outputs of over 5 photoelectrons per MeV, were obtained from both sides of a BC 408 scintillator with five 2-mm BCF 92 fast green waveshifting fibers using a Hamamatsu green extended R 580-17 PM. With a reflector at one end of the fibers, attenuation lengths of over 10 ms were obtained. First results using inexpensive acrylic scintillators with this method are presented. >

Low cross-talk fiber readout of scintillating detectors

After evaluating and optimizing several multichannel photomultiplier tubes and small low-cost side-window photomultiplier tubes, the authors have devised two methods which, depending on the particular application, are viable readout systems for a small to moderate number of fibers. The new 16-channel Hamamatsu R4760 photomultiplier tube offers, when timing information is utilized, the lowest near-neighbour cross-talk ( >

Optimization of the use of small inexpensive side-window photomultiplier tubes for scintillator readout

The 931B is a small inexpensive side-window photomultiplier tube (PMT) which has recently been found to be useful for the readout of scintillators. We present the results of a study to obtain improved performance from the PMT by facilitating the transport of light to the reflection type photocathode. Particular attention is given for the use of these PMTs for the readout of light guides, waveshifting and scintillating fibers. A CCD camera was positioned behind a glass envelope to simulate the photocathode to aid in quantifying the optimum combination of optical coupling and aiming of the fiber. We will also report on tests comparing a similar side-window PMT, the Thorn EMI model 9781B to the 931B. Tests on the operation of the side-window PMT at several orientations in a uniform magnetic field will also be reported. Comparisons between the side-window PMT and a RCA 31000M head-on tube will also be reported. >