Spectral analysis of fundamental signal and noise performances in photoconductors for mammography

Journal Article · Tue May 15 00:00:00 EDT 2012 · Medical Physics

DOI:https://doi.org/10.1118/1.3702455· OSTI ID:22098841

Kim, Ho Kyung; Lim, Chang Hwy; Tanguay, Jesse; Yun, Seungman; Cunningham, Ian A. ^[1]

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1. School of Mechanical Engineering, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea and Center for Advanced Medical Engineering Research, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of)

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{sub 2}, PbI{sub 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{sub 2}, PbI{sub 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{sup -2}, a-Se, HgI{sub 2}, and PbI{sub 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.

• OSTI ID: 22098841
• Journal Information: Medical Physics, Vol. 39, Issue 5; Other Information: (c) 2012 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
62 RADIOLOGY AND NUCLEAR MEDICINE
BIOMEDICAL RADIOGRAPHY
CADMIUM COMPOUNDS
COMPUTERIZED SIMULATION
ENERGY ABSORPTION
ENERGY SPECTRA
LEAD IODIDES
LEAD OXIDES
MAMMARY GLANDS
MERCURY IODIDES
MONTE CARLO METHOD
NOISE
QUANTUM EFFICIENCY
SEMICONDUCTOR DETECTORS
SIGNAL-TO-NOISE RATIO
SILICON
TELLURIUM COMPOUNDS
X RADIATION
X-RAY SPECTRA
ZINC COMPOUNDS