Fundamental x-ray interaction limits in diagnostic imaging detectors: Spatial resolution

被引:49
作者
Hajdok, G. [1 ,2 ,3 ]
Battista, J. J. [2 ,3 ]
Cunningham, I. A. [1 ,3 ,4 ,5 ]
机构
[1] Robarts Res Inst, Imaging Res Labs, London, ON N6A 5K8, Canada
[2] London Hlth Sci Ctr, London Reg Canc Program, London, ON N6A 4L6, Canada
[3] Univ Western Ontario, Dept Med Biophys & Oncol, London, ON N6A 3K7, Canada
[4] London Hlth Sci Ctr, Dept Diagnost Radiol, London, ON N6A 5W9, Canada
[5] London Hlth Sci Ctr, Dept Nucl Med, London, ON N6A 5W9, Canada
基金
加拿大健康研究院;
关键词
modulation transfer function; diagnostic x-ray detectors; diagnostic x-ray imaging;
D O I
10.1118/1.2924219
中图分类号
R8 [特种医学]; R445 [影像诊断学];
学科分类号
1002 ; 100207 ; 1009 ;
摘要
The practice of diagnostic x-ray imaging has been transformed with the emergence of digital detector technology. Although digital systems offer many practical advantages over conventional film-based systems, their spatial resolution performance can be a limitation. The authors present a Monte Carlo study to determine fundamental resolution limits caused by x-ray interactions in four converter materials: Amorphous silicon (a-Si), amorphous selenium, cesium iodide, and lead iodide. The "x-ray interaction" modulation transfer function (MTF) was determined for each material and compared in terms of the 50% MTF spatial frequency and Wagner's effective aperture for incident photon energies between 10 and 150 keV and various converter thicknesses. Several conclusions can be drawn from their Monte Carlo study. (i) In low-Z (a-Si) converters, reabsorption of Compton scatter x rays limits spatial resolution with a sharp MTF drop at very low spatial frequencies (< 0.3 cycles/mm), especially above 60 keV; while in high-Z materials, reabsorption of characteristic x rays plays a dominant role, resulting in a mid-frequency (1-5 cycles/mm) MTF drop. (ii) Coherent scatter plays a minor role in the x-ray interaction MTF. (iii) The spread of energy due to secondary electron (e.g., photoelectrons) transport is significant only at very high spatial frequencies. (iv) Unlike the spread of optical light in phosphors, the spread of absorbed energy from x-ray interactions does not significantly degrade spatial resolution as converter thickness is increased. (v) The effective aperture results reported here represent fundamental spatial resolution limits of the materials tested and serve as target benchmarks for the design and development of future digital x-ray detectors. (C) 2008 American Association of Physicists in Medicine.
引用
收藏
页码:3180 / 3193
页数:14
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