Contrast-to-Noise Ratio and Low-Contrast Object Resolution on Full- and Low-Dose MDCT: SAFIRE Versus Filtered Back Projection in a Low-Contrast Object Phantom and in the Liver
Contrast-to-Noise Ratio and Low-Contrast Object Resolution on Full- and Low-Dose MDCT: SAFIRE Versus Filtered Back Projection in a Low-Contrast Object Phantom and in the Liver
复制标题
DOI：
10.2214/ajr.11.7421
复制
发表时间：
2012-07-01
影响因子：
5
通讯作者：
Vachani, Neil
中科院分区：
文献类型：
--
作者：
Baker, Mark E.;Dong, Frank;Vachani, Neil
目标。本文的目的是评价肯定正弦图迭代重建(SAFIRE)与滤波反投影(FBP)相比对比度噪声比(CNR)的影响，并确定SAFIRE是否改善了低对比度目标体模和肝脏在全剂量和低剂量检查中的低对比度目标检测或显着性。使用由双源多层螺旋CT扫描仪组成的单源对低对比度目标体模分别进行100%、70%、50%和30%剂量扫描，原始数据用Safire和FBP重建。使用双源多层螺旋CT对22例患者进行肝脏CT平扫。用FBP重建两管(100%剂量)的原始数据，用FBP和Safire重建一管(50%剂量)的数据。在体模和肝脏中测量CNR。噪声、对比度和CNR使用配对学生t检验进行比较。6名读者评估了患者数据中幻影和肝下腔静脉的球体探测和显着性。结果：与100%剂量的FBP相比，使用SAFIRE的70%和50%剂量的模型降低了噪声，增加了CNR。在肝脏中，50%剂量的SAFIRE与100%和50%剂量的FBP100%和50%剂量相比，CNR的平均改善分别是31.4%和88%(p<；0.001)。使用SAFIRE(p<；0.001)改进了球体对象检测和显眼效果。然而，在较低剂量下，较小的球体在FBP和Safire图像上都会变得模糊。服用SAFIRE的患者中，67.4%的患者肝血管显着性改善(p<；0.001)，与100%剂量的患者相比，38.6%的患者改善(p=0.085)。作为检测的预测指标，仅CNR的判别能力(c指数，0.970)与分析剂量、病变大小、衰减差异和重建技术的模型(c指数，0.978)相似。结论：SAFIRE重建的低剂量扫描具有更高的CNR。Safire提高低对比度目标检测和显着性的能力取决于辐射剂量水平。在低辐射剂量下，无论采用何种重建技术，低对比度对象都是不可见的。
OBJECTIVE. The purpose of this article is to evaluate the effect of sinogram-affirmed iterative reconstruction (SAFIRE) on contrast-to-noise ratio (CNR) compared with filtered back projection (FBP) and to determine whether SAFIRE improves low-contrast object detection or conspicuity in a low-contrast object phantom and in the liver on full-and low-dose examinations.SUBJECTS AND METHODS. A low-contrast object phantom was scanned at 100%, 70%, 50%, and 30% dose using a single-source made of a dual-source MDCT scanner, with the raw data reconstructed with SAFIRE and FBP. Unenhanced liver CT scans in 22 patients were performed using a dual-source MDCT. The raw data from both tubes (100% dose) were reconstructed using FBP, and data from one tube (50% dose) were reconstructed using both FBP and SAFIRE. CNR was measured in the phantom and in the liver. Noise, contrast, and CNR were compared using paired Student t tests. Six readers assessed sphere detection and conspicuity in the phantom and liver-inferior vena cava conspicuity in the patient data. The phantom and patient data were assessed using multiple-variable logistic regression.RESULTS. The phantom at 70% and 50% doses with SAFIRE had decreased noise and increased CNR compared with the 100% dose with FBP. In the liver, the mean CNR improvement at 50% dose with SAFIRE compared with FBP was 31.4% and 88% at 100% and 50% doses, respectively (p < 0.001). Sphere object detection and conspicuity improved with SAFIRE (p < 0.001). However, smaller spheres were obscured on both FBP and SAFIRE images at lower doses. Liver-vessel conspicuity improved with SAFIRE over 50%-dose FBP in 67.4% of cases (p < 0.001), and versus 100%-dose FBP, improved in 38.6% of cases (p = 0.085). As a predictor for detection, CNR alone had a discriminatory ability (c-index, 0.970) similar to that of the model that analyzed dose, lesion size, attenuation difference, and reconstruction technique (c-index, 0.978).CONCLUSION. Lower dose scans reconstructed with SAFIRE have a higher CNR. The ability of SAFIRE to improve low-contrast object detection and conspicuity depends on the radiation dose level. At low radiation doses, low-contrast objects are invisible, regardless of reconstruction technique.