Vedantham S, Karellas A, Suryanarayanan S, D'Orsi C J, Hendrick R E
Department of Radiology, UMass Memorial Health Care, University of Massachusetts Medical School, Worcester 01655, USA.
J Digit Imaging. 2000 Nov;13(4):191-9. doi: 10.1007/BF03168394.
An amorphous silicon-based full-breast imager for digital mammography was evaluated for detector stability over a period of 1 year. This imager uses a structured CsI:TI scintillator coupled to an amorphous silicon layer with a 100-micron pixel pitch and read out by special purpose electronics. The stability of the system was characterized using the following quantifiable metrics: conversion factor (mean number of electrons generated per incident x-ray), presampling modulation transfer function (MTF), detector linearity and sensitivity, detector signal-to-noise ratio (SNR), and American College of Radiology (ACR) accreditation phantom scores. Qualitative metrics such as flat field uniformity, geometric distortion, and Society of Motion Picture and Television Engineers (SMPTE) test pattern image quality were also used to study the stability of the system. Observations made over this 1-year period indicated that the maximum variation from the average of the measurements were less than 0.5% for conversion factor, 3% for presampling MTF over all spatial frequencies, 5% for signal response, linearity and sensitivity, 12% for SNR over seven locations for all 3 target-filter combinations, and 0% for ACR accreditation phantom scores. ACR mammographic accreditation phantom images indicated the ability to resolve 5 fibers, 4 speck groups, and 5 masses at a mean glandular dose of 1.23 mGy. The SMPTE pattern image quality test for the display monitors used for image viewing indicated ability to discern all contrast steps and ability to distinguish line-pair images at the center and corners of the image. No bleeding effects were observed in the image. Flat field uniformity for all 3 target-filter combinations displayed no artifacts such as gridlines, bad detector rows or columns, horizontal or vertical streaks, or bad pixels. Wire mesh screen images indicated uniform resolution and no geometric distortion.
对一款用于数字乳腺摄影的非晶硅基全乳腺成像仪进行了为期1年的探测器稳定性评估。该成像仪采用结构化的碘化铯铊闪烁体，与像素间距为100微米的非晶硅层耦合，并由专用电子设备读出。使用以下可量化指标来表征系统的稳定性：转换因子（每入射X射线产生的平均电子数）、预采样调制传递函数（MTF）、探测器线性度和灵敏度、探测器信噪比（SNR）以及美国放射学会（ACR）认证体模评分。还使用了诸如平场均匀性、几何畸变和电影电视工程师协会（SMPTE）测试图案图像质量等定性指标来研究系统的稳定性。在这1年期间的观察表明，转换因子的测量平均值的最大变化小于0.5%，所有空间频率下预采样MTF的最大变化为3%，信号响应、线性度和灵敏度的最大变化为5%，所有3种靶-滤过组合在7个位置的SNR最大变化为12%，ACR认证体模评分的最大变化为0%。ACR乳腺摄影认证体模图像表明，在平均腺体剂量为1.23毫戈瑞时能够分辨出5根纤维、4个斑点组和5个肿块。用于图像查看的显示监视器的SMPTE图案图像质量测试表明，能够辨别所有对比度等级，并且能够在图像中心和角落区分线对图像。图像中未观察到渗色效应。所有3种靶-滤过组合的平场均匀性均未显示出诸如网格线、探测器坏行或坏列、水平或垂直条纹或坏像素等伪影。丝网屏图像显示分辨率均匀且无几何畸变。
