Improving Cadmium Zinc Telluride Detectors through In-Depth Analysis and Collaboration. KYLE KOHMAN (Kansas State University Manhattan, KS 66502) ALEKSEY BOLOTNIKOV (Brookhaven National Laboratory, Upton, NY, 11973)

Cadmium Zinc Telluride (CdZnTe) crystal is a material that shows great potential for detection of gamma and X-rays because it provides a high gamma ray stopping power, high energy resolution, and can be operated at room temperature while remaining much more compact than other detector assemblies. These properties make it useful for applications in fields such as nuclear medical imaging, Homeland Security, and astronomy. The ability to consistently produce good quality crystals has not yet been achieved, thus holding back the potential impact of these devices on current technology. This study gives a better understanding to the properties of CdZnTe crystals for detection in hopes to achieve consistent production of superior quality crystals for detectors. Vendors send Brookhaven National Laboratory (BNL) samples of their CdZnTe material to test quality and to seek advice for improvements. These crystals go through an array of tests to give the vendor a detailed understanding of what their crystals' characteristics are. By using the X-ray beam from the National Synchrotron Light Source (NSLS) at BNL, the energy transmission of the crystal is analyzed. X-ray diffraction is also performed at the NSLS to attain a topographical map of the crystal. Infrared images are taken to observe precipitates in the material. The crystal is then polished and made into a detector. Its detection capabilities are analyzed by counting radiation at different voltages. The data is then analyzed to try and observe correlations between the crystal properties and the detector performance. A better understanding of what material properties affect detectors is achieved. Feedback is then provided to the vendors of the material to help them improve their crystal growth techniques. Eventually this will lead to production of improved quality CdZnTe crystal, making CdZnTe detectors more useful. This allows for the implementation of better detectors in industry and the advancement of other fields like nuclear medical imaging, Homeland Security and astronomy.

Microbeam Radiation Therapy in the Treatment of Tumors. NATAN LENJO (Bronx Community College Bronx, NY 10453) AVRAHAM DILMANIAN (Brookhaven National Laboratory, Upton, NY, 11973)

Radiation therapy is one of the principal methods used in the treatment of tumors, especially brain tumors. The problem faced by the current methods of treatment is the limitation brought about by the radiosensitivity of normal tissues surrounding the tumor, therefore placing considerable constraints in the adequate delivery of the radiation dose(s) to the tumor. Microbeam Radiation Therapy (MRT) appears to address this problem. MRT uses an array of parallel, thin planar slices of synchrotron-generated x-rays (microbeams) and is commonly administered in a single dose in the treatment of animal tumors. The irradiation of tumors with microbeams appears to spare normal tissue, including the central nervous system, while damaging the tumor. To demonstrate the application of MRT in the treatment of brain tumors, male rats, 200-225 g, were injected with 1x104 cultured 9L gliosarcoma (9LGS) cells into their striatum 4 mm left of the midline, at the bregma level. These cells were implanted 5 mm beneath the surface of the skull using a 27-gauge needle. It took 14 days for the cultured cells to grow into tumors measuring 4 mm in diameter. The rats with 9L gliosarcoma brain tumors were exposed to a microbeams with a median energy of 120 keV. A total of 32 tumor-inoculated rats were used in this experiment; 24 were irradiated and 8 were left unirradiated as controls. The rats were monitored closely after the irradiation, euthanizing any that showed signs of neurological disability. In the previous MRT studies histological examinations 4 months after the irradiations or later showed that no tumor or tumor residue were visible, and that the brain tissues showed no significant level of damage. Those earlier results suggested that MRT can destroy tumors at a relatively high efficacy rate with little or no normal tissue damage. However, the present study is still ongoing and no conclusive results can be reached at this time.