Division of Radiology, Department of Medical Technology, Kyushu University Hospital, Fukuoka, Japan.
Department of Oral and Maxillofacial Radiology, Faculty of Dental Science, Kyushu University, Fukuoka, Japan.
Dentomaxillofac Radiol. 2020 Sep 1;49(6):20190462. doi: 10.1259/dmfr.20190462. Epub 2020 Apr 29.
This study aimed to propose an improved scan method to shorten irradiation time and reduce radiation exposure.
The maxilla of a human head CT phantom and a Catphan phantom were used for qualitative and quantitative assessment, respectively. The phantoms were scanned by a 160-row multidetector CT scanner using volumetric and helical scanning. In volumetric scanning, the tube current varied from 120 to 60 to 30 to 20 mA with a tube voltage of 120 kV. Images were reconstructed with a bone kernel using iterative reconstruction (IR) and filtered back projection. As a reference protocol, helical scanning was performed using our clinical setting with 120 kV. Two dental radiologists independently graded the quality of dental images using a 4-point scale (4, superior to reference; 1, unacceptable). For the quantitative assessment, we assessed the system performance from each scan.
There was no significant difference between the image quality of volumetric scanning using the 60 mA protocol reconstructed with IR and that of the reference (3.08 and 3.00, = 0.3388). The system performance values at 1.0 cycles/mm of volumetric scanning and 60 mA protocol reconstructed with IR and reference were 0.0038 and 0.0041, respectively. The effective dose of volumetric scanning using the 60 mA protocol was 51.8 µSv, which is a 64.2% reduction to that of the reference.
We proposed an improved scan method resulting in a 64.2% reduction of radiation dose with one-fourth of irradiation time by combining volumetric scanning and IR technique in multidetector CT.
本研究旨在提出一种改良的扫描方法，以缩短照射时间，减少辐射暴露。
使用头部 CT 体模和 Catphan 体模对人体上颌进行定性和定量评估。使用容积扫描和螺旋扫描对体模进行 160 排多层 CT 扫描仪扫描。在容积扫描中，管电流分别为 120mA、60mA、30mA 和 20mA，管电压为 120kV。使用骨核进行图像重建，采用迭代重建（IR）和滤波反投影。作为参考方案，使用我们的临床设置进行螺旋扫描，管电压为 120kV。两位牙科放射科医生使用 4 分制（4，优于参考；1，不可接受）独立对牙齿图像质量进行评分。对于定量评估，我们从每次扫描中评估系统性能。
IR 重建的 60mA 协议容积扫描的图像质量与参考图像质量无显著差异（3.08 与 3.00， = 0.3388）。IR 重建的 60mA 协议容积扫描和参考的 1.0 周期/毫米系统性能值分别为 0.0038 和 0.0041。60mA 协议容积扫描的有效剂量为 51.8µSv，比参考剂量降低了 64.2%。
我们提出了一种改良的扫描方法，通过结合容积扫描和 IR 技术，在多排 CT 中可将辐射剂量降低 64.2%，照射时间缩短为四分之一。
