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High Resolution Active Pixel Sensor X-Ray Detectors for Digital Breast Tomosynthesis

机译：用于数字乳房断层合成的高分辨率有源像素传感器X射线探测器

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摘要

Current large area x-ray detectors for digital breast tomosynthesis (DBT) are based on the amorphous silicon (a-Si:H) passive pixel sensor (PPS) technology. However, PPS detectors suffer from a limited resolution and high electronic noise. In this dissertation, we propose high resolution large area active pixel sensor (APS) x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) and amorphous In-Sn-Zn-O (a-ITZO) thin-film transistor (TFT) technologies to improve the imager resolution and noise properties.;We evaluated the two-dimensional (2D) x-ray imaging performance as measured by the modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE) for both 75 microm (Dexela 2923 MAM) and 50 microm pixel pitch (DynAMITe) CMOS APS x-ray detectors. Excellent imaging performance (DQE in the range of 0.7 -- 0.3) has been achieved over the entire spatial frequency range (0 -- 6.7 mm-1) at low air kerma below 10 microGy using the 75 microm pixel pitch Dexela 2923 MAM detector. The 50 microm pixel pitch DyAMITe detector has further extended the spatial resolution of the detector to 10 mm-1 with a low electronic noise of 150 e-. Also, a 2D cascaded system analysis model has been developed to describe the signal and noise transfer for the CMOS APS x-ray imaging systems. We also implemented three-dimensional (3D) cascaded system analysis to simulated the 3D MTF, NPS and DQE characteristics using DBT radiation conditions and acquisition geometries. The 3D cascaded system analysis for the DynAMITe detector was integrated with an object task function, a medical imaging display model, and the human eye contrast sensitivity function to calculate the detectability index and area under the ROC curve (AUC). It has been demonstrated that the display pixel pitch and zoom factor should be optimized to improve the AUC for detecting high contrast objects such as microcalcifications. Also, detector electronic noise of smaller than 300 e- and a high display maximum luminance (>1000 cd/cm2) are desirable to distinguish microcalcifications of 150 microm or smaller in size. For low contrast object detection, a medical imaging display with a minimum of 12 bits gray levels is needed to realize accurate luminance levels. A wide projection angle range (≥ +/-30°) combined with the image gray level magnification could improve the detectability for low contrast objects especially when the anatomical background noise is high.;CMOS APS x-ray detectors demonstrate both a high pixel resolution and low electronic noise, but are challenging to be fabricated in a large detector size greater than the wafer scale. Alternatively, current-mode APS (C-APS) based on a-ITZO TFTs was proposed for DBT due to the high gain, low noise, and capability to realize a large detector area. Specifically, we fabricated a-ITZO TFTs and achieved a high field-effect mobility of >30 cm2/Vs. We have also evaluated the electrical performance of a 50 microm pixel pitch a-ITZO TFT C-APS combined with an a-Si:H p+-i-n+ photodiode using SPICE simulation. The proposed C-APS circuit demonstrates a high charge gain of 885 with data line loadings considered. A pixel circuit layout and fabrication process have also been suggested. Finally, noise analysis has been applied to the a-ITZO TFT C-APS. A low electronic noise of around 239 e- has been established.;The research presented in this thesis indicates that APS x-ray detectors based on both CMOS and a-ITZO TFT technologies are promising for next generation DBT systems.
机译：当前用于数字乳腺断层合成（DBT）的大面积X射线检测器基于非晶硅（a-Si：H）无源像素传感器（PPS）技术。但是，PPS检测器的分辨率有限且电子噪声高。本文提出了基于互补金属氧化物半导体（CMOS）和非晶In-Sn-Zn-O（a-ITZO）薄膜晶体管的高分辨率大面积有源像素传感器（APS）x射线探测器。 （TFT）技术来提高成像仪的分辨率和噪声性能。我们评估了二维（2D）X射线成像性能，该性能通过调制传递函数（MTF），噪声功率谱（NPS）和探测量子效率（ DQE）适用于75微米（Dexela 2923 MAM）和50微米像素间距（DynAMITe）CMOS APS X射线检测器。使用75微米像素间距的Dexela 2923 MAM检测器，在低于10 microGy的低空气比释动能下，已在整个空间频率范围（0-6.7 mm-1）上实现了出色的成像性能（DQE在0.7-0.3范围内）。 50微米像素间距的DyAMITe检测器将检测器的空间分辨率进一步扩展至10 mm-1，并具有150 e-的低电子噪声。同样，已经开发了2D级联系统分析模型来描述CMOS APS X射线成像系统的信号和噪声传输。我们还实施了三维（3D）级联系统分析，以使用DBT辐射条件和采集几何来模拟3D MTF，NPS和DQE特性。 DynAMITe检测器的3D级联系统分析与目标任务功能，医学成像显示模型和人眼对比敏感度功能集成在一起，以计算可检测性指标和ROC曲线（AUC）下的面积。已经证明，应该优化显示像素的间距和缩放系数，以改善用于检测高对比度对象（如微钙化）的AUC。同样，小于300 e-的检测器电子噪声和高显示最大亮度（> 1000 cd / cm2）也是可取的，以区分尺寸为150微米或更小的微钙化。对于低对比度物体检测，需要具有至少12位灰度级的医学成像显示器以实现准确的亮度级。宽的投影角度范围（≥+/- 30°）与图像灰度放大倍率相结合，可以改善低对比度对象的可检测性，尤其是在解剖背景噪声较高的情况下。CMOS APS X射线检测器显示出高像素分辨率电子噪声低，但要以大于晶圆尺寸的大型检测器制造挑战。替代地，由于高增益，低噪声和实现大检测器面积的能力，针对DBT提出了基于a-ITZO TFT的电流模式APS（C-APS）。具体来说，我们制造了a-ITZO TFT，并实现了大于30 cm2 / Vs的高场效应迁移率。我们还使用SPICE仿真评估了50微米像素间距的a-ITZO TFT C-APS与a-Si：H p + -i-n +光电二极管的电气性能。考虑到数据线负载，建议的C-APS电路显示出885的高电荷增益。还提出了像素电路布局和制造工艺。最后，噪声分析已应用于a-ITZO TFT C-APS。已经建立了大约239 e-的低电子噪声。本文的研究表明，基于CMOS和a-ITZO TFT技术的APS X射线探测器对于下一代DBT系统是有希望的。

著录项

  • 作者

    Zhao, Chumin.;

  • 作者单位

    University of Michigan.;

  • 授予单位 University of Michigan.;
  • 学科 Electrical engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 207 p.
  • 总页数 207
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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