Departments of Abdominal Imaging and Intervention and Urology, Massachusetts General Hospital, 55 Fruit St, White 270, Boston, MA 02114.
Radiology. 2012 Oct;265(1):158-66. doi: 10.1148/radiol.12112470. Epub 2012 Aug 13.
To evaluate the performance of computed tomographic (CT) examinations at 80 and 100 kV with tube current-time products of 75-150 mA and the effect of adaptive statistical iterative reconstruction (ASIR) on CT image quality in patients with urinary stone disease.
In this HIPAA-compliant institutional review board-approved study, verbal consent for prospective low-dose CT and waivers of consent for retrospective review of CT scans were obtained. Between November 2010 and April 2011, 25 patients (15 men, 10 women; mean age, 35 years) with urolithiasis underwent 64-section multidetector CT with 75-150 mA and noise index of 30. Modified protocol was based on body weight (<200 lb [90 kg], 80 kV; >200 lb [90 kg], 100 kV). Images of 5-mm section thickness were reconstructed with filtered back projection (FBP) and 60% and 80% ASIR techniques, with 3-mm coronal and sagittal reformations. Two readers independently reviewed FBP and ASIR data sets for image quality (scale, 1-5), noise (scale , 1-3), and calculi (number, size, location). Confidence levels for urolithiaisis and alternate diagnoses were rated (scale, 1-3). In 13 patients, FBP CT images acquired with the reference standard departmental protocol were available for comparison. Radiation dose was compared between imaging series. Statistical analysis was performed with Wilcoxon signed rank and paired t tests.
Modified-protocol FBP images showed low image quality (score, 2.5), with improvement on modified-protocol ASIR images (score, 3.4) (P=.03). All 33 stones (mean diameter, 6.1 mm; range, 2-28 mm) at modified-protocol CT were diagnosed by both readers. In 20 of 25 patients (80%), ASIR images were rated adequate for rendering other diagnoses in the abdomen (score, 2.0), as opposed to FBP images (score, 1.3). Mean radiation dose for modified-protocol CT was 1.8 mGy (1.3 mGy for patients<200 lb; 2.3 mGy for patients>200 lb) in comparison with 9.9 mGy for reference-protocol CT (P=.001).
Image quality improvements with ASIR at reduced radiation dose of 1.8 mGy enabled effective evaluation of urinary calculi without substantially affecting diagnostic confidence. © RSNA, 2012.
评估在管电流时间乘积为 75-150 mA 时，使用 80 和 100 kV 的 CT 检查的性能，以及自适应统计迭代重建（ASIR）对尿路结石病患者 CT 图像质量的影响。
本 HIPAA 合规性机构审查委员会批准的研究中，患者均口头同意进行低剂量 CT 检查，同时也豁免了对 CT 扫描的回顾性审查的同意。2010 年 11 月至 2011 年 4 月，25 例尿路结石病患者（15 例男性，10 例女性；平均年龄 35 岁）接受了 64 层多层 CT 检查，管电流时间乘积为 75-150 mA，噪声指数为 30。改良方案基于体重（<200 磅[90kg]，80kV；>200 磅[90kg]，100kV）。5mm 层厚的图像使用滤波反投影（FBP）和 60%和 80%的 ASIR 技术重建，冠状和矢状位重建 3mm。两名读者分别独立对 FBP 和 ASIR 数据集进行图像质量（1-5 分）、噪声（1-3 分）和结石（数量、大小、位置）评估。对结石病和其他诊断的置信度（1-3 分）进行了评分。在 13 例患者中，可获得参考标准部门方案采集的 FBP CT 图像进行比较。比较了两种成像系列的辐射剂量。采用 Wilcoxon 符号秩和配对 t 检验进行统计学分析。
改良方案 FBP 图像的图像质量较低（评分为 2.5），改良方案 ASIR 图像的图像质量有所改善（评分为 3.4）（P=.03）。两名读者均能诊断出改良方案 CT 上所有 33 颗结石（平均直径 6.1mm；范围 2-28mm）。在 25 例患者中的 20 例（80%）中，ASIR 图像的诊断其他腹部病变的能力为适当（评分 2.0），而 FBP 图像的能力为一般（评分 1.3）。与参考方案 CT 的 9.9mGy 相比，改良方案 CT 的平均辐射剂量为 1.8mGy（<200 磅患者的剂量为 1.3mGy；>200 磅患者的剂量为 2.3mGy）（P=.001）。
ASIR 可在降低 1.8mGy 的辐射剂量的情况下提高图像质量，从而在不显著影响诊断信心的情况下有效评估尿路结石。
