使用非线性自适应滤波器降低胸部CT的辐射剂量

Radiation dose reduction for chest CT with non-linear adaptive filters.

作者信息

Singh Sarabjeet, Digumarthy Subba R, Back Anni, Shepard Jo-anne O, Kalra Mannudeep K

机构信息

Massachusetts General Hospital Imaging, Boston, MA, USA.

出版信息

Acta Radiol. 2013 Mar 1;54(2):169-74. doi: 10.1258/ar.2012.120045. Epub 2012 Nov 26.

DOI:10.1258/ar.2012.120045

PMID:23185071

Abstract

BACKGROUND

CT radiation dose reduction results in increased noise or graininess of images which affects the diagnostic information. One of the approaches to lower radiation exposure to patients is to reduce image noise with the use of image processing software in low radiation dose images.

PURPOSE

To assess image quality and accuracy of non-linear adaptive filters (NLAF) at low dose chest CT.

MATERIAL AND METHODS

In an IRB approved prospective study, 24 patients (mean age, 63 ± 7.3 years; M:F ratio, 11:13) gave informed consent for acquisition of four additional chest CT image series at 150, 110, 75, and 40 mAs (baseline image series) on a 64-slice MDCT over an identical 10-cm length. NLAF was used to process three low dose (110, 75, and 40 mAs) image series (postprocessed image series). Two radiologists reviewed baseline and postprocessed images in a blinded manner for image quality. Objective noise, CT attenuation values, patient weight, transverse diameters, CTDIvol, and DLP were recorded. Statistical analysis was performed using parametric and non-parametric tests for comparing postprocessed and baseline images.

RESULTS

No lesions were missed on baseline or postprocessed CT images (n = 80 lesions, 73 lesions <1 cm). At 40 mAs, subjective noise in mediastinal window settings were graded as unacceptable in baseline images and acceptable in postprocessed images. Visibility of smaller structures improved from suboptimal visibility in baseline images at 40 mAs to excellent in postprocessed images at 40 mAs. No major artifacts were seen due to NLAF postprocessing, except for minor beam hardening artifacts not affecting diagnostic decision-making (14/22) in both baseline and postprocessed image series. Diagnostic confidence for chest CT was improved to fully confident in postprocessed images at 40 mAs. Compared to baseline images, postprocessing reduced objective noise by 26% (14.2 ± 4.7/19.2 ± 6.4), 31.5% (15.2 ± 4.7/22.2 ± 5.7), and 41.5% (16.9 ± 6/28.9 ± 10.2) at 110 mAs, 75 mAs, and 40 mAs tube current-time product levels.

CONCLUSION

Applications of NLAF can help reduce tube current down to 40 mAs for chest CT while maintaining lesion conspicuity and image quality.

摘要

背景

CT辐射剂量降低会导致图像噪声增加或颗粒感增强，从而影响诊断信息。降低患者辐射暴露的方法之一是在低辐射剂量图像中使用图像处理软件来降低图像噪声。

目的

评估非线性自适应滤波器（NLAF）在低剂量胸部CT中的图像质量和准确性。

材料与方法

在一项经机构审查委员会批准的前瞻性研究中，24例患者（平均年龄63±7.3岁；男:女比例为11:13）签署知情同意书，在一台64层MDCT上，于相同的10厘米长度范围内采集四个额外的胸部CT图像系列，管电流分别为150、110、75和40 mAs（基线图像系列）。使用NLAF处理三个低剂量（110、75和40 mAs）图像系列（后处理图像系列）。两名放射科医生以盲法方式对基线图像和后处理图像的质量进行评估。记录客观噪声、CT衰减值、患者体重、横径、容积CT剂量指数（CTDIvol）和剂量长度乘积（DLP）。使用参数检验和非参数检验对后处理图像和基线图像进行统计学分析。

结果

在基线或后处理CT图像上均未漏诊病变（共80个病变，73个病变<1厘米）。在40 mAs时，纵隔窗设置下基线图像的主观噪声被评为不可接受，而后处理图像的主观噪声被评为可接受。较小结构的可视性从40 mAs基线图像中的次优可视性提高到40 mAs后处理图像中的极佳可视性。除了在基线和后处理图像系列中均出现的不影响诊断决策的轻微硬化伪影（14/22）外，未发现因NLAF后处理导致的主要伪影。在40 mAs时，胸部CT的诊断信心在后处理图像中提高到完全有信心。与基线图像相比，在110 mAs、75 mAs和40 mAs管电流-时间乘积水平下，后处理分别将客观噪声降低了26%（14.2±4.7/19.2±6.4）、31.5%（15.2±4.7/22.2±5.7）和41.5%（16.9±6/28.9±10.2）。