Modeling and evaluation of a high-resolution CMOS detector for cone-beam CT of the extremities.
Modeling and evaluation of a high-resolution CMOS detector for cone-beam CT of the extremities.
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对四肢的锥束CT进行高分辨率CMOS探测器的建模和评估。
DOI：
10.1002/mp.12654
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发表时间：
2018-01
期刊：
影响因子：
3.8
通讯作者：
Zbijewski W
中科院分区：
文献类型：
--
作者：
Cao Q;Sisniega A;Brehler M;Stayman JW;Yorkston J;Siewerdsen JH;Zbijewski W
由于互补金属氧化物半导体（CMOS） x射线探测器具有高空间分辨率、低电子噪声和快速扫描时间的特点，对四肢锥形束CT （CBCT）中骨小梁微结构的定量评估将受益。我们研究了CMOS传感器在末端CBCT中的性能，特别是关于薄（<0.7 mm）闪烁体提供更高空间分辨率的潜在优势。建立了考虑CsI:Tl闪烁体厚度影响的CMOS x射线探测器级联系统模型。模拟研究采用名义极限CBCT采集协议（90 kVp， 0.126 mAs/投影）进行。考虑了闪烁体厚度（0.35-0.75 mm）、像素尺寸（0.05-0.4 mm）、焦斑尺寸（0.05-0.7 mm）、倍率（1.1-2.1）和剂量（15-40 mGy）的范围。对CMOS和a- si:H平板探测器（FPD）配置的可探测性指数进行了评估，用于一系列成像任务，强调与特征尺寸aobj相关的空间频率。实验验证在紧凑的骨科CBCT系统（SAD = 43.1 cm, SDD = 56.0 cm，与Carestream OnSight 3D系统相匹配）的CBCT试验台上进行。试验台研究涉及一个0.3毫米焦斑x射线源和两个CMOS探测器（Dalsa Xineos-3030HR， 0.099毫米像素间距）-一个具有标准CsI:Tl厚度0.7毫米（C700），一个具有定制的0.4毫米厚闪烁体（C400）。每个探测器的调制传递函数（MTF）、探测量子效率（DQE）和尸体膝盖（15 mGy）的CBCT扫描测量结果均得到。对于高频任务（特征尺寸为~0.06 mm，与小梁尺寸一致），C700 CMOS探测器的最佳检测能力是a-Si:H FPD在四肢CBCT标称系统几何形状下的4倍。这是由于CMOS传感器的电子噪声降低了约5倍，从而可以在更小的像素尺寸下实现输入量子限制成像。高频任务的最佳像素尺寸为CMOS <0.1 mm，而a- si:H FPD为~ 0.14mm。对于这种精细的像素间距，可以通过使用更薄的闪烁体来减少光传播模糊来提高精细特征的可检测性。与C700相比，C400配置的0.06 mm特征的可探测性增加了22%。测量到MTF在50%调制（f50）时的频率有所改善，从C700的1.8 lp/mm增加到C400的2.5 lp/mm。对于~2 mm−1以上的频率，C400配置也实现了与C700相同或更好的DQE。尸体标本的图像证实C400传感器改善了小梁的可视化。与a- si:H FPDs相比，CMOS探测器的小像素尺寸提高了高分辨率末端CBCT的性能，特别是当与定制的0.4 mm厚闪烁体相结合时。结果表明，在肢体CBCT中采用CMOS探测器有利于人体小梁微观结构的定量成像。
Quantitative assessment of trabecular bone microarchitecture in extremity cone-beam CT (CBCT) would benefit from the high spatial resolution, low electronic noise, and fast scan time provided by complementary metal-oxide semiconductor (CMOS) x-ray detectors. We investigate the performance of CMOS sensors in extremity CBCT, in particular with respect to potential advantages of thin (<0.7 mm) scintillators offering higher spatial resolution. A cascaded systems model of a CMOS x-ray detector incorporating the effects of CsI:Tl scintillator thickness was developed. Simulation studies were performed using nominal extremity CBCT acquisition protocols (90 kVp, 0.126 mAs/projection). A range of scintillator thickness (0.35–0.75 mm), pixel size (0.05–0.4 mm), focal spot size (0.05–0.7 mm), magnification (1.1–2.1) and dose (15–40 mGy) was considered. Detectability index was evaluated for both CMOS and a-Si:H flat-panel detector (FPD) configurations for a range of imaging tasks emphasizing spatial frequencies associated with feature size aobj. Experimental validation was performed on a CBCT test-bench in the geometry of a compact orthopedic CBCT system (SAD = 43.1 cm, SDD = 56.0 cm, matching that of the Carestream OnSight 3D system). The test-bench studies involved a 0.3 mm focal spot x-ray source and two CMOS detectors (Dalsa Xineos-3030HR, 0.099 mm pixel pitch) - one with the standard CsI:Tl thickness of 0.7 mm (C700) and one with a custom 0.4 mm thick scintillator (C400). Measurements of modulation transfer function (MTF), detective quantum efficiency (DQE), and CBCT scans of a cadaveric knee (15 mGy) were obtained for each detector. Optimal detectability for high-frequency tasks (feature size of ~0.06 mm, consistent with the size of trabeculae) was ~4× for the C700 CMOS detector compared to the a-Si:H FPD at nominal system geometry of extremity CBCT. This is due to ~5× lower electronic noise of a CMOS sensor, which enables input quantum-limited imaging at smaller pixel size. Optimal pixel size for high-frequency tasks was <0.1 mm for a CMOS, compared to ~ 0.14mm for an a-Si:H FPD. For this fine pixel pitch, detectability of fine features could be improved by using a thinner scintillator to reduce light spread blur. A 22% increase in detectability of 0.06 mm features was found for the C400 configuration compared to C700. An improvement in the frequency at 50% modulation (f50) of MTF was measured, increasing from 1.8 lp/mm for C700 to 2.5 lp/mm for C400. The C400 configuration also achieved equivalent or better DQE as C700 for frequencies above ~2 mm−1. Images of cadaver specimens confirmed improved visualization of trabeculae with the C400 sensor. The small pixel size of CMOS detectors yields improved performance in high-resolution extremity CBCT compared to a-Si:H FPDs, particularly when coupled with a custom 0.4 mm thick scintillator. The results indicate that adoption of a CMOS detector in extremity CBCT can benefit applications in quantitative imaging of trabecular microstructure in humans.
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影响因子：
3.8
作者：
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通讯作者：
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