Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO 63110, USA.
Invest Radiol. 2013 Aug;48(8):584-9. doi: 10.1097/RLI.0b013e318289f918.
The purpose of this study was to compare the effects of combined automated tube voltage selection and automated tube current modulation on radiation dose and image quality in small-sized phantoms undergoing computed tomography angiography (CTA) with the use of automated current modulation alone.
Three semianthropomorphic phantoms, corresponding to a neonate, a small child, and a small adult, underwent simulated abdominal CTA using an automated tube voltage selection technology, which simultaneously optimizes kilovoltage (in kilovolt [peak]) and tube-current/milliamperage (in milliampere-second) on the basis of the patient topogram and clinical task. The phantoms were scanned with 2 protocols: protocol A, using the combination of automated kilovoltage and milliamperage, and protocol B, using only automated milliamperage with the standard 120 kV(p). Radiation doses were measured for each phantom, and the measurements were then used to estimate volume computed tomography dose index. Image noise and iodine contrast, contrast-to-noise ratio, and the relative dose factor were assessed. Differences were tested using paired t tests, and percentage differences for various technical factors and the phantom sizes were calculated.
The computed tomography dose index was significantly lower in protocol A (mean, 3.3 mGy) compared with that in protocol B (mean, 7.7 mGy), representing a 56.0% dose reduction (P = 0.01). In protocol A, tube potential dropped from 120 to 70 kV(p) in the small and medium phantoms and to 80 kV(p) in the large phantom. For each phantom size, image noise and iodine contrast increased significantly in protocol A relative to those in protocol B (P = 0.03 and P < 0.01, respectively). Corresponding contrast-to-noise ratio values increased by 9.1% in protocol A relative to those in protocol B (P = 0.04). The relative dose factor values for protocol A relative to those for protocol B were 31%, 36%, and 44% for the small, medium, and large phantoms, respectively.
Combined use of automated kilovoltage selection and automated tube current modulation is more effective for reducing radiation dose and maintaining image quality during simulated pediatric CTA than is automated tube current modulation in isolation.
本研究旨在比较在使用自动管电流调制（仅使用自动管电流调制）的基础上，联合使用自动管电压选择和自动管电流调制对行 CT 血管造影（CTA）的小型体模的辐射剂量和图像质量的影响。
对 3 个半人体模型（对应于新生儿、儿童和小成人）进行模拟腹部 CTA，使用自动管电压选择技术，该技术根据患者的体表图和临床任务同时优化千伏（峰值千伏）和管电流/毫安秒（毫安秒）。使用 2 种方案对体模进行扫描：方案 A，联合使用自动千伏和毫安，方案 B，仅使用自动毫安，管电压为 120 kV(p)。测量每个体模的辐射剂量，然后使用测量值来估计容积 CT 剂量指数。评估图像噪声和碘对比度、对比噪声比和相对剂量因子。使用配对 t 检验测试差异，计算各种技术因素和体模尺寸的百分比差异。
方案 A 的 CT 剂量指数（mean，3.3 mGy）明显低于方案 B（mean，7.7 mGy），剂量降低 56.0%（P = 0.01）。在方案 A 中，中、小型体模的管电压从 120 kV(p)降至 70 kV(p)，大型体模降至 80 kV(p)。对于每个体模尺寸，方案 A 的图像噪声和碘对比度均明显高于方案 B（P = 0.03 和 P < 0.01）。相应的对比噪声比分别提高了 9.1%（P = 0.04）。方案 A 的相对剂量因子分别比方案 B 高 31%、36%和 44%，适用于小型、中型和大型体模。
与单独使用自动管电流调制相比，联合使用自动千伏选择和自动管电流调制在模拟儿科 CTA 中更有效地降低辐射剂量并保持图像质量。
