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Spectral analysis of fundamental signal and noise performances in photoconductors for mammography
Author(s) -
Kim Ho Kyung,
Lim Chang Hwy,
Tanguay Jesse,
Yun Seungman,
Cunningham Ian A.
Publication year - 2012
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3702455
Subject(s) - detective quantum efficiency , quantum efficiency , noise (video) , physics , quantum noise , optics , monte carlo method , materials science , x ray detector , detector , optoelectronics , computational physics , quantum , image quality , mathematics , image (mathematics) , quantum mechanics , statistics , artificial intelligence , computer science
Purpose: This study investigates the fundamental signal and noise performance limitations imposed by the stochastic nature of x‐ray interactions in selected photoconductor materials, such as Si, a ‐Se, CdZnTe, HgI 2 , PbI 2 , PbO, and TlBr, for x‐ray spectra typically used in mammography.Methods: It is shown how Monte Carlo simulations can be combined with a cascaded model to determine the absorbed energy distribution for each combination of photoconductor and x‐ray spectrum. The model is used to determine the quantum efficiency, mean energy absorption per interaction, Swank noise factor, secondary quantum noise, and zero‐frequency detective quantum efficiency (DQE).Results: The quantum efficiency of materials with higher atomic number and density demonstrates a larger dependence on convertor thickness than those with lower atomic number and density with the exception of a ‐Se. The mean deposited energy increases with increasing average energy of the incident x‐ray spectrum. HgI 2 , PbI 2 , and CdZnTe demonstrate the largest increase in deposited energy with increasing mass loading and a ‐Se and Si the smallest. The best DQE performances are achieved with PbO and TlBr. For mass loading greater than 100 mg cm −2 , a ‐Se, HgI 2 , and PbI 2 provide similar DQE values to PbO and TlBr.Conclusions: The quantum absorption efficiency, average deposited energy per interacting x‐ray, Swank noise factor, and detective quantum efficiency are tabulated by means of graphs which may help with the design and selection of materials for photoconductor‐based mammography detectors. Neglecting the electrical characteristics of photoconductor materials and taking into account only x‐ray interactions, it is concluded that PbO shows the strongest signal‐to‐noise ratio performance of the materials investigated in this study.