Fukao Mari, Kawamoto Kiyosumi, Matsuzawa Hiroaki, Honda Osamu, Iwaki Takeshi, Doi Tsukasa
Division of Radiology, Department of Medical Technology, Osaka University Hospital, 2-15, Yamadaoka, Suita, Osaka, 565-0871, Japan,
Radiol Phys Technol. 2015 Jan;8(1):46-52. doi: 10.1007/s12194-014-0285-y. Epub 2014 Aug 15.
We aimed to optimize the exposure conditions in the acquisition of soft-tissue images using dual-energy subtraction chest radiography with a direct-conversion flat-panel detector system. Two separate chest images were acquired at high- and low-energy exposures with standard or thick chest phantoms. The high-energy exposure was fixed at 120 kVp with the use of an auto-exposure control technique. For the low-energy exposure, the tube voltages and entrance surface doses ranged 40-80 kVp and 20-100 % of the dose required for high-energy exposure, respectively. Further, a repetitive processing algorithm was used for reduction of the image noise generated by the subtraction process. Seven radiology technicians ranked soft-tissue images, and these results were analyzed using the normalized-rank method. Images acquired at 60 kVp were of acceptable quality regardless of the entrance surface dose and phantom size. Using a repetitive processing algorithm, the minimum acceptable doses were reduced from 75 to 40 % for the standard phantom and to 50 % for the thick phantom. We determined that the optimum low-energy exposure was 60 kVp at 50 % of the dose required for the high-energy exposure. This allowed the simultaneous acquisition of standard radiographs and soft-tissue images at 1.5 times the dose required for a standard radiograph, which is significantly lower than the values reported previously.
我们旨在利用直接转换平板探测器系统的双能减影胸部X线摄影技术，优化软组织图像采集的曝光条件。使用标准或厚胸部模型，在高能量和低能量曝光下分别采集两张胸部图像。高能量曝光通过自动曝光控制技术固定在120 kVp。对于低能量曝光，管电压和体表入射剂量分别在40 - 80 kVp和高能量曝光所需剂量的20 - 100%范围内。此外，采用重复处理算法来减少减影过程中产生的图像噪声。七名放射技师对软组织图像进行评分，并使用归一化秩方法对这些结果进行分析。无论体表入射剂量和模型大小如何，在60 kVp下采集的图像质量均可接受。使用重复处理算法，标准模型的最小可接受剂量从75%降至40%，厚模型降至50%。我们确定最佳低能量曝光为60 kVp，剂量为高能量曝光所需剂量的50%。这使得能够以标准X线片所需剂量的1.5倍同时采集标准X线片和软组织图像，这一数值显著低于先前报道的值。
