[en] An imaging gamma detector was developed using a 5 inch diameter Hamamatsu R3292 position sensitive PMT and GSO crystal scintillator plates from Hitachi. Plate sizes from 4 x 4 cm to 8 x 8 cm and thickness from 1.25 mm to 2.5 mm were used to detect 28-35 keV photons from ¹²⁵I and 140 kev gamma's from ^99mTc. Several novel features of the detector were investigated including improvement of detector resolution by using anode wire sections and truncated center-of-gravity calculations. After the PSPMT's readout was optimized a resolution of about ∼5mm at sign 140 keV was obtained using only fourteen (7x,7y) anode wire sections in lieu of the standard 28 x 28 individual crossed-wires. Due to good obtained overall energy resolution, efficient scatter rejection is expected by placing just one simple energy window on scintillation signals coming from the detector. Measurements were made with point and linear sources as well as thyroid and compressed breast phantoms with simulated lesions. The phantoms contained appropriate concentrations of ^99mTc emitting 140 keV gamma radiation. The detector combines good performance with small size and economical makeup. After additional phantom tests and software improvement we are planning to use it first as a small field-of-view small animal gamma imager

[en] A scintillating fiber hodoscope has been built for use as a photon beam profiler in the bremsstrahlung tagged photon beam in Hall B of the Thomas Jefferson National Accelerator Facility (Jefferson Lab). The device consists of a linear array of 64 2-2 mm2 scintillating fibers glued to a corresponding set of light guide fibers. Both fiber types use double-clad technology for maximum intensity. The light guide fibers are gently bent into a square array of holes and air-gap coupled to four compact position-sensitive photomultipliers (16 channel Hamamatsu R5900-M16). Custom electronics amplifies and converts the analog outputs to ECL pulses which are counted by VME-based scalars. The device consisting of the fibers, photomultipliers, and electronics is sealed within a light-tight aluminum box. Two modules make up a beam imaging 2-D system. The system has been tested successfully during an experimental run

[en] This paper presents a gas scintillator built and tested to monitor and control the extracted proton beam intensity for the Loma Linda medical accelerator. The device is potentially capable of measuring intensity to 1% accuracy at a 100-kHz bandwidth. The intensity monitor is extremely resistant to radiation damage and contributes less than 2 mrad of multiple scattering to the passing proton beam. The monitor consists of a gas cell filled with krypton and coupled to an EMI 9902 photomultiplier with a quartz window

[en] Motion-corrected awake animal imaging is needed for normal-state investigations of models of neurological disease and brain activity. The awake animal brain SPECT/CT system, AwakeSPECT at Johns Hopkins University has in the past used a single gamma camera for imaging. Enhancements have been made by adding a pinhole collimator to the second gamma camera at the opposite side which has been previously equipped parallel hole collimator. Geometry calibration was performed using a custom built quality control phantom containing three Co-57 point sources and applied to the tomographic reconstruction code. Hot-rod phantom scans with Tc-99m were performed to test sensitivity and resolution improvements. The reconstruction results show significant resolution and sensitivity improvements.

[en] Within the past few years, a concerted effort has been mounted to increase the radiation tolerance of organic scintillators for use in detectors at the proposed SSC and LHC high luminosity hadron colliders. In particualr, there is a general interest in using plastic scintillaters in the form of optical fibers for both tracking and calorimetric applications. Such a fiber would have a diameter of about 0.5-1.0 mm and consist of a scintillating core (typically doped polystyrene) surrounded by a thin cladding of lower index of refraction material (usually acrylic) to provide the required waveguide character. It is accepted that standard blue-emitting fibers such as SCSFF-38 and BCF-10 will suffer unacceptable levels of damage in the collider environment. As a result of this, newer, more radiation tolerant scintillators have been formulated. A low dose rate irradiation of selected plastic scintillating fibers has been completed (700 rad/hr to 1 Mrad). A second run is planned in order to make a more thorough study. This first run has indicated that 3HF-doped fibers suffer significantly less damage than a set of standard blue-emitting scintillating fibers

[en] Recently small animal research utilizing nuclear medicine based imaging has been combined with structural anatomical imaging from x-ray radiography providing a powerful tool for animal researchers. The addition of a third modality is the goal of our instrumentation development. Thomas Jefferson National Accelerator Facility and Case Western Reserve University have been collaborating on the development of a planar imaging system which in addition to radiopharmaceutical based functional imaging and x-ray radiography structural imaging also allows for the in vivo bioluminescence imaging thus providing another functional imaging modality. For the gamma camera we use is a Hamamatsu position sensitive photomultiplier tube coupled to a pixellated NaI(TI) scintillator array with individual crystal elements 1 mm x 1 mm x 5 mm in size and a 0.25 mm septum between each element. The gamma camera has a 10 cm diameter active area and can be used for 125I, 99mT and 111In radionuclide imaging. To acquire anatomical information we are using a Rad-Icon Shad-o-Box X-ray detector that provides a field of view of 5 cm x 10 cm. The x-ray source is a Source-Ray compact x-ray generator. We are using a Princeton Instruments cooled CCD based detector for the imaging of the bio-distribution of bioluminescence. All three imaging instruments will be integrated into a single light tight/ x-ray tight enclosure.

[en] A low dose rate evaluation of several scintillators and wavelength shifters of interest to the CEBAF program was performed with a ⁶⁰Co line source to a total dose of 160 Gray at a rate of 0.5 Gy/hr in a slowly flowing oxygen atmosphere. The samples included the following: (1) a 2 meter piece of Bicron BC412 scintillator being extensively used in the CEBAF Large Acceptance Spectrometer, (2) a 1 meter long piece of green scintillator doped with a uniquely fast green fluor (G2), (3) wavelength shifting fiber doped also with G2, and (4) grooved acrylic-based scintillator that is readout with the WLS fiber. The data indicates that the BC412 shows no loss in intrinsic light output, but does have an attenuation loss amounting to 10% at 1 meter and 16% at 2 meters. The fast green scintillator (and fibers) showed no damage. When read out by WLS fibers, the acrylic scintillator displayed a loss in intrinsic light output, but no change in attenuation

[en] A prototype for a practical and economical breast imaging system for cancer detection is currently under development at Jefferson Lab. The latest advances in bright, fast, crystal scintillators, compact position-sensitive photomultipliers (PSPMT), and high-performance digitizing and readout electronics are being used to develop a compact imager based on Positron Emission Tomography (PET). To facilitate the performance demands of the detector as well as the high number of readout channels, the data acquisition system is built around an intelligent, self-contained, VME form-factor

[en] We describe an ultra-high density scintillating fiber and tungsten calorimeter used as an active beam-dump for electrons. Data showing the calorimeter response to electrons with momenta between 50 and 350 GeV/c are presented. 9 figs

[en] Jefferson Lab, Hampton University and the Riverside Regional Medical Center are collaborating in a clinical study employing a dual modality imaging system utilizing scintimammography and digital radiography. The purpose of the study is to obtain clinical data on the reliability of scintimammography in predicting the malignancy of suspected breast lesions with the ultimate goal to reduce the number of false positives associated with conventional x-ray mammography. The scintimammography gamma camera is a custom built mini gamma camera with an active area of 5.3 cm x 5.3 cm based on a 2x2 array of Hamamatsu R7600-C8 position sensitive photomultiplier tubes. The spatial resolution of the gamma camera at the collimator surface is <4 mm FWHM and the sensitivity is 4000 cps/mCi. Preliminary results are that of the six cases that indicated a lesion with high uptake of MiraLuma (^99mTc-sestamibi) five were positive for cancer. Out of a total of 25 patients in the study, all cases negative for MiraLuma uptake were confirmed negative via the biopsy pathology. The scintimammography results indicate that the lesions become visible with the mini gamma camera within 3 minutes post injection of MiraLuma