Share Email Print

Proceedings Paper

Absorbers for medical x-ray detectors with optimum spatial resolution: a simulation study
Author(s): Martin Hoheisel; Jurgen Giersch; Michaela Mitschke; Philipp Bernhardt
Format Member Price Non-Member Price
PDF $17.00 $21.00

Paper Abstract

The requirements for medical X-ray detectors tend towards higher spatial resolution, especially for mammography. Therefore, we have investigated common absorber materials with respect to the possible intrinsic limitations of their spatial resolution. Primary interaction of an incident X-ray quantum is followed by a series of processes: Rayleigh scattering, Compton effect, or the generation of fluorescence photons and subsequent electrons. Lateral diffusion of carriers relative to their drift towards the electrodes also broadens the point-spread function. One consequence is that the spatial resolution of the detector, expressed in terms of the modulation transfer function (MTF), is reduced. Monte Carlo simulations have been carried out for spectra with tube voltages of 28-120 kV using the program ROSI (Roentgen Simulation) based on the well-established EGS4 algorithm. The lateral distribution of deposited energy has been calculated in typical materials such as Se, CdTe, HgI2, and PbI2 and used to determine the line spread function. The complex absorption process is found to determine the spatial resolution of the detector considerably. The spectrum at energies closely above the K-edge of the absorber material tends to result in a reduced MTF. At energies above 50 keV, electron energy loss increasingly reduces spatial resolution in the high frequency range. The influence of fluorescence is strongest in the 5-20 lp/mm range. If a very high spatial resolution is required, a well-adapted semiconductor should be applied.

Paper Details

Date Published: 6 May 2004
PDF: 10 pages
Proc. SPIE 5368, Medical Imaging 2004: Physics of Medical Imaging, (6 May 2004); doi: 10.1117/12.535305
Show Author Affiliations
Martin Hoheisel, Siemens Medical Solutions, Inc. (Germany)
Jurgen Giersch, Friedrich-Alexander Univ. Erlangen-Nurnberg (Germany)
Michaela Mitschke, Friedrich-Alexander Univ. Erlangen-Nurnberg (Germany)
Philipp Bernhardt, Siemens Medical Solutions, Inc. (Germany)

Published in SPIE Proceedings Vol. 5368:
Medical Imaging 2004: Physics of Medical Imaging
Martin J. Yaffe; Michael J. Flynn, Editor(s)

© SPIE. Terms of Use
Back to Top