AbstractID: 6542 Title: New transfer relation describing non-elementary stages in
medical imaging detectors
Linear systems cascade analysis is a useful tool to study the imaging
characteristics of medical x-ray detectors. In this analysis, the interactions of imaging
quanta with the detector are broken down into a series of stages. The propagation of
signal and noise through each stage can then be calculated using suitable transfer
relations. Transfer relations have been developed for elementary stages: an amplification
stage, where each quantum creates multiple quanta with no change in location, and a
dislocation stage, where each quantum is moved to a new location (but the total number
of quanta is conserved). These elementary stages have been successful in describing
various detectors in medical imaging. In general, however, a quantum can create many
secondary quanta, each dislocated to a different location. In some cases it may be
impossible to further subdivide these interactions into elementary stages. For this reason
we derive a new transfer relation which governs stages with multiple correlated
amplifications and dislocations. We illustrate the use of this relation with an example:
megavoltage imaging with a metal/phosphor detector. In this case, many optical photons
are created at various positions along the tracks of ionizing radiation, which undergoes
significant lateral transport at megavoltage energies. We calculate the detective quantum
efficiency (DQE) using the new cascade equation and Monte Carlo techniques, and show
good agreement with experimental data.