基于自动衰减的胸腹部 CT 血管造影管电压选择：提高剂量效率。

Automated attenuation-based tube potential selection for thoracoabdominal computed tomography angiography: improved dose effectiveness.

机构信息

Department of Radiology, University Hospital Zurich, Zurich, Switzerland.

出版信息

Invest Radiol. 2011 Dec;46(12):767-73. doi: 10.1097/RLI.0b013e3182266448.

DOI:10.1097/RLI.0b013e3182266448

PMID:21730872

Abstract

PURPOSE

To introduce a novel algorithm of automated attenuation-based tube potential selection and to assess its impact on image quality and radiation dose of body computed tomography angiography (CTA).

MATERIALS AND METHODS

In all, 40 patients (mean age 71±11.8 years, body mass index (BMI) 25.7±3.8 kg/m², range 18.8-33.8 kg/m²) underwent 64-slice thoracoabdominal CTA (contrast material: 80 mL, 5 mL/s) using an automated tube potential selection algorithm (CAREkV), which optimizes tube-potential (70-140 kV) and tube-current (138.8±18.6 effective mAs, range 106-177 mAs) based on the attenuation profile of the topogram and on the diagnostic task. Image quality was semiquantitatively assessed by 2 blinded and independent readers (scores 1: excellent to 5: nondiagnostic). Attenuation and noise were measured by another 2 blinded and independent readers. Contrast-to-noise ratio was calculated. The CT dose index (CTDIvol) was recorded and compared with the estimated CTDIvol of a standard 120 kV protocol without using the algorithm in each patient. Selected tube potentials were correlated with BMI and attenuation of the topogram.

RESULTS

Diagnostic image quality was obtained in all patients (excellent: 14; good: 21; moderate: 5; interreader agreement: κ=0.78). Mean attenuation, noise, and contrast-to-noise ratio were 260.8±63.5 Hounsfield units, 15.5±3.3 Hounsfield units, and 14±4.2, respectively, with good to excellent agreement between readers (r=0.50-0.99, P<0.01 each). Automated attenuation-based tube potential selection resulted in a kV-reduction from 120 to 100 kV in 23 patients and to 80 kV in 1 patient, whereas tube potential increased to 140 kV in 1 patient. Automatically selected tube potential showed a significant correlation with both BMI (r=0.427, P<0.05) and attenuation of the topogram (r=0.831, P<0.001). CTDIvol (7.95±2.6 mGy) was significantly lower when using the algorithm compared with the standard 120 kV protocol (10.59±1.8 mGy, P<0.001), corresponding to an overall dose reduction of 25.1%.

CONCLUSION

Automated attenuation-based tube potential selection based on the attenuation profile of the topogram is feasible, provides a diagnostic image quality of body CTA, and reduces overall radiation dose by 25% as compared with a standard protocol with 120 kV.

摘要

目的

介绍一种基于自动衰减的管电压选择的新算法，并评估其对体部 CT 血管造影（CTA）图像质量和辐射剂量的影响。

材料与方法

共 40 例患者（平均年龄 71±11.8 岁，体重指数（BMI）25.7±3.8 kg/m²，范围 18.8-33.8 kg/m²）接受了 64 层胸腹 CTA（对比剂：80 mL，5 mL/s），使用了一种自动管电压选择算法（CAREkV），该算法根据定位图的衰减曲线和诊断任务优化管电压（70-140 kV）和管电流（138.8±18.6 有效 mAs，范围 106-177 mAs）。图像质量由 2 位盲法和独立的读者进行半定量评估（评分 1：极好至 5：无法诊断）。衰减和噪声由另外 2 位盲法和独立的读者进行测量。计算对比噪声比。记录 CT 剂量指数（CTDIvol），并与每位患者未使用算法的标准 120 kV 方案的估计 CTDIvol 进行比较。选择的管电压与 BMI 和定位图的衰减相关。

结果

所有患者均获得了诊断性图像质量（极好：14；好：21；中等：5；读者间一致性：κ=0.78）。平均衰减、噪声和对比噪声比分别为 260.8±63.5 Hounsfield 单位、15.5±3.3 Hounsfield 单位和 14±4.2，读者间一致性良好（r=0.50-0.99，P<0.01）。自动基于衰减的管电压选择导致 23 例患者的管电压从 120 kV 降低至 100 kV，1 例患者降低至 80 kV，而 1 例患者的管电压升高至 140 kV。自动选择的管电压与 BMI（r=0.427，P<0.05）和定位图的衰减（r=0.831，P<0.001）均有显著相关性。与标准 120 kV 方案相比，使用算法时 CTDIvol（7.95±2.6 mGy）显著降低（P<0.001），总剂量降低 25.1%。