Improved Detector for Electronic Radiotherapy Imaging

This work is directed at developing an improved x-ray imaging detector for high-energy radiotherapy applications and exploring its use as a two-dimensional dosimeter in-quantitative treatmentverification. A high-performance portal imaging system will be a key factor in reducing localizationproblems, thereby, contributing to lower recurrence of tumors at the margins of the treatment field. Wewill assemble an imaging system, using high density clear scintillating glass as the sensor and a slowscan CCD for read out. Glass scintillators have densities approaching 4 g/cm3, a value significantlygreater than granular phosphor screens. The slow scan CCD will provide signal-to-noise ratios greaterthan possible with video tubes. We will perform tests to determine spatial resolution, signal-to-noiseratio, and Detective Quantum Efficiency in comparison to that of the Siemens Beam View Plus system,a conventional system based on metal/phosphor and electron beam video tube technology. Bothsystems will be calibrated with respect to dose, accuracy, and precision. The Phase I program willinclude experimental x-ray tests with the Rando phantom which could be useful in determining dose tothe patient estimated from the exit dose distribution measured with the high performance portal imagingsystem.