Matsubara Kosuke, Takata Tadanori, Kobayashi Masanao, Kobayashi Satoshi, Koshida Kichiro, Gabata Toshifumi
1 Department of Quantum Medical Technology, Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan.
2 Department of Radiological Technology, Kanazawa University Hospital, Kanazawa, Ishikawa, Japan.
AJR Am J Roentgenol. 2016 Aug;207(2):354-61. doi: 10.2214/AJR.15.15404. Epub 2016 May 25.
The purpose of this study was to compare the effects of tube current modulation between single- and dual-energy CT with a second-generation dual-source scanner.
Custom-made elliptic polymethylmethacrylate phantoms for slim and large patients were used. Absorbed radiation dose at the central point of the phantoms was measured with a solid-state detector while the phantoms were scanned in single-energy (120 kV) and dual-energy (100/Sn140, 80/Sn140, and 140/80 kV) modes with a second-generation dual-source CT scanner. Tube current modulation was activated in both modes, and quality reference tube current-time settings of 150, 300, 450, and 600 mAs were selected. Scanning was performed three times under the same conditions, and image noise was evaluated by measuring the SD of CT numbers in four separate regions of three adjacent images of the phantoms.
Absorbed dose increased and image noise decreased with an increase in quality reference tube current-time setting when the slim phantom was scanned. For the large phantom, the radiation dose and noise level reached a plateau above quality reference tube current-time settings of 300 mAs for 100/Sn140 kV and 450 mAs for 120 kV. The radiation dose was small and the noise level was large with 80/Sn140 kV compared with that obtained with 120 and 100/Sn140 kV at all quality reference tube current-time settings.
When a large phantom is scanned with 100/Sn140 kV, exposure demand for tube current modulation exceeds system limits at a lower quality reference tube current-time setting than for scanning 120 kV.
本研究旨在比较使用第二代双源扫描仪时，单能量CT与双能量CT的管电流调制效果。
使用为体型瘦小和体型较大患者定制的椭圆形聚甲基丙烯酸甲酯体模。在使用第二代双源CT扫描仪以单能量（120 kV）和双能量（100/Sn140、80/Sn140和140/80 kV）模式扫描体模时，用固态探测器测量体模中心点的吸收辐射剂量。两种模式均激活管电流调制，并选择150、300、450和600 mAs的质量参考管电流-时间设置。在相同条件下进行三次扫描，并通过测量体模三张相邻图像四个单独区域的CT值标准差来评估图像噪声。
扫描瘦小体模时，随着质量参考管电流-时间设置增加，吸收剂量增加而图像噪声降低。对于体型较大的体模，对于100/Sn140 kV，辐射剂量和噪声水平在质量参考管电流-时间设置高于300 mAs时达到平台期；对于120 kV，在质量参考管电流-时间设置高于450 mAs时达到平台期。在所有质量参考管电流-时间设置下，与120 kV和100/Sn140 kV相比，80/Sn140 kV时辐射剂量小且噪声水平大。
当使用100/Sn140 kV扫描体型较大的体模时，与扫描120 kV相比，管电流调制的曝光需求在较低的质量参考管电流-时间设置下就超过了系统极限。
