比较散射抑制和低对比度性能的扫描均衡数字射线摄影术（SEDR）、狭缝扫描数字射线摄影术和全视野数字射线摄影术系统对胸部体模成像。

Comparison of scatter rejection and low-contrast performance of scan equalization digital radiography (SEDR), slot-scan digital radiography, and full-field digital radiography systems for chest phantom imaging.

机构信息

Department of Imaging Physics, Digital Imaging Research Laboratory, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030-4009, USA.

出版信息

Med Phys. 2011 Jan;38(1):23-33. doi: 10.1118/1.3519903.

DOI:10.1118/1.3519903

PMID:21361171

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC3017579/

Abstract

PURPOSE

To investigate and compare the scatter rejection properties and low-contrast performance of the scan equalization digital radiography (SEDR) technique to the slot-scan and conventional full-field digital radiography techniques for chest imaging.

METHODS

A prototype SEDR system was designed and constructed with an a-Se flat-panel (FP) detector to improve image quality in heavily attenuating regions of an anthropomorphic chest phantom. Slot-scanning geometry was used to reject scattered radiation without attenuating primary x rays. The readout scheme of the FP was modified to erase accumulated scatter signals prior to image readout. A 24-segment beam width modulator was developed to regulate x-ray exposures regionally and compensate for the low x-ray flux in heavily attenuating regions. To measure the scatter-to-primary ratios (SPRs), a 2 mm thick lead plate with a 2-D array of aperture holes was used to measure the primary signals, which were then subtracted from those obtained without the lead plate to determine scatter components. A 2-D array of aluminum beads (3 mm in diameter) was used as the low-contrast objects to measure the contrast ratios (CRs) and contrast-to-noise ratios (CNRs) for evaluating the low-contrast performance in chest phantom images. A set of two images acquired with the same techniques were subtracted from each other to measure the noise levels. SPRs, CRs, and CNRs of the SEDR images were measured in four anatomical regions of chest phantom images and compared to those of slot-scan images and full-field images acquired with and without antiscatter grid.

RESULTS

The percentage reduction of SPR (percentage of SPRs reduced with scatter removal/ rejection methods relative to that for nongrid full-field imaging) averaged over four anatomical regions was measured to be 80%, 83%, and 71% for SEDR, slot-scan, and full-field with grid, respectively. The average CR over four regions was found to improve over that for nongrid full-field imaging by 259%, 279%, and 145% for SEDR, slot-scan, and full-field with grid, respectively. The average CNR over four regions was found to improve over that for nongrid full-field imaging by 201% for SEDR as compared to 133% for the slot-scan technique and 14% for the antiscatter grid method.

CONCLUSIONS

Both SEDR and slot-scan techniques outperformed the antiscatter grid method used in standard full-field radiography. For imaging with the same effective exposure, the SEDR technique offers no advantage over the slot-scan method in terms of SPRs and CRs. However, it improves CNRs significantly, especially in heavily attenuating regions. The improvement of low-contrast performance may help improve the detection of the lung nodules or other abnormalities and may offer SEDR the potential for dose reduction in chest radiography.

摘要

目的

研究并比较扫描均衡数字射线摄影术（SEDR）技术与狭缝扫描和传统全视野数字射线摄影技术在胸部成像中的散射线抑制特性和低对比度性能。

方法

设计并构建了一个原型 SEDR 系统，该系统使用 a-Se 平板（FP）探测器，以提高在人体胸部模拟体模的高衰减区域的图像质量。狭缝扫描几何形状用于在不衰减初级 X 射线的情况下抑制散射线。修改了 FP 的读出方案，以便在图像读出之前擦除累积的散射信号。开发了一个 24 段的光束宽度调制器，以在区域上调节 X 射线曝光并补偿高衰减区域中的低 X 射线通量。为了测量散射与初级射线之比（SPRs），使用 2 毫米厚的带有二维孔径阵列的铅板来测量初级信号，然后从没有铅板的情况下获得的信号中减去这些信号，以确定散射分量。使用 2 毫米直径的二维铝珠阵列作为低对比度物体，以测量胸部模拟体模图像的对比度比（CR）和对比噪声比（CNR），以评估低对比度性能。通过从彼此中减去获得的一组具有相同技术的两幅图像来测量噪声水平。在胸部模拟体模图像的四个解剖区域中测量了 SEDR 图像的 SPRs、CRs 和 CNRs，并与狭缝扫描图像以及带有和不带有防散射格栅的全视野图像进行了比较。

结果

在四个解剖区域中，相对于无格栅全视野成像，SPR（使用散射去除/抑制方法相对于无格栅全视野成像降低的 SPR 百分比）的平均降低百分比为 80%、83%和 71%，分别为 SEDR、狭缝扫描和带格栅的全视野。在四个区域中，平均 CR 相对于无格栅全视野成像的改善分别为 259%、279%和 145%，用于 SEDR、狭缝扫描和带格栅的全视野。在四个区域中，平均 CNR 相对于无格栅全视野成像的改善，SEDR 为 201%，而狭缝扫描技术为 133%，防散射格栅方法为 14%。

结论

SEDR 和狭缝扫描技术均优于标准全视野射线摄影中使用的防散射格栅方法。对于相同有效曝光的成像，SEDR 技术在 SPRs 和 CRs 方面与狭缝扫描方法相比没有优势。然而，它显著提高了 CNR，尤其是在高衰减区域。低对比度性能的提高可能有助于提高肺结节或其他异常的检测能力，并可能为胸部 X 射线摄影带来 SEDR 降低剂量的潜力。