3D position sensing on UltraPeRL CdZnTe detectors
Experimental results of depth and lateral position sensing on UltraPeRL pixellated CdZnTe detectors using signal ratios are presented. Each detector employs one CdZnTe crystal of 20 mm times 20 mm times 5 mm with 8 times 8 pixel electrodes fabricated on the anode surface. The anode pixel pitch is 2.4 mm. The signal ratios are calculated using the signals induced on the collecting pixel and the eight neighboring pixels. The signal on each collecting pixel is then corrected for depth of interaction using the signal ratios. We obtained 7.6%, 4.2% and 2.5% FWHM energy resolution at 122 keV, 356 keV and 662 keV, respectively.
Event classification in 3D position sensitive semiconductor detectors
A set of analytical methods for pixelated 3D position sensitive semiconductor detectors has been developed to make better measurements of gamma-rays in the 30 keV to 3 MeV energy range. The ability to classify pixel charge sharing, x-ray escape, pair production, and Compton scattering allows for more accurate and efficient energy reconstruction and Compton imaging routines. The techniques are based on the analysis of digitized preamplifier waveforms from the electrodes that sense charge following an interaction. Accurate identification of an event is based on the comparison of an expected detector response with precise measurements of an interaction’s resulting signal amplitude, shape, and timing characteristics. A tungsten collimator is used to demonstrate the accuracy of the classification methods. Experimental results taken with large volume CZT and HgI2 detectors are compared with system simulations.
A technique for large-field, superficial electron therapy.
The application of electron beams to radiation therapy has received increased attention in recent years. This interest stems largely from the special characteristics of the electron depth-dose distribution; the fall-off in depth dose near the end of the range of the electrons is particularly rapid for electron beams having energies less than about 10 Mev. Such an electron beam is suitable for the treatment of widespread, superficial lesions, where it is desirable to minimize the dose to deep tissues. All the common sources of super-voltage x-rays, apart from radioactive substances, are inherently capable of producing an external beam of electrons, though with varying degrees of complexity. Electrons of about the energy suitable for superficial therapy (several Mev) may be used to produce an x-ray beam which is sufficiently penetrating for the treatment of even the deepest lesions. The Stanford medical linear accelerator was designed to provide both x-rays and electron beams. The accelerator and its applic...