Qurashi Abdulaziz A, Rainford Louise A, Alshamrani Khalid M, Foley Shane J
Department of Diagnostic Radiologic Technology, College of Applied Medical Sciences, Taibah University, Madinah, Saudi Arabia.
Radiography & Diagnostic Imaging, School of Medicine, University College Dublin, Dublin, Ireland.
Radiat Prot Dosimetry. 2019 Nov 30;185(1):17-26. doi: 10.1093/rpd/ncy212.
The aim of this study was to evaluate how iterative reconstruction can compensate for the noise increase in low radiation dose abdominal computed tomography (CT) technique for large size patients and the general impact of obesity on abdominal organ doses and image quality in CT. An anthropomorphic phantom layered with either none or a single layer of 3-cm- thick circumferential animal fat packs to simulate obese patients was imaged using a 128MDCT scanner. Abdominal protocols (n = 12) were applied using automatic tube current modulation (ATCM) with various quality reference mAs (150, 200, 250 and 300). kVs of 100, 120 and 140 were used for each mAs selection. Metal oxide semiconductor field effect transistor dosimeters (MOSFET) measured internal organ dose. All images produced were reconstructed with filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE) (3, 4 and 5) and objective noise was measured within three regions of interest at the level of L4-L5. Organ doses varied from 0.12 to 41.9 mGy, the spleen received the highest doses for both phantom sizes. Compared to the phantom simulating average size, the obese phantom was associated with up to twofold increase in delivered mAs, dose length product (DLP) and computed tomography dose index (CTDIvol) for the matched mAs selection (p < 0.05). However, organ dose increased by 50% only. The use of 100 kV resulted in a 40% lower dose (p < 0.05) compared to 120 kV and the associated noise increase was improved by SAFIRE (5) use, which resulted in 60% noise reduction compared to FBP (p < 0.05). When combined with iterative reconstruction, low kV is feasible for obese patients to optimise radiation dose and maintain objective image quality.
本研究的目的是评估迭代重建如何补偿大尺寸患者低辐射剂量腹部计算机断层扫描（CT）技术中噪声的增加，以及肥胖对CT腹部器官剂量和图像质量的总体影响。使用128层MDCT扫描仪对带有或不带有单层3厘米厚环形动物脂肪包以模拟肥胖患者的人体模型进行成像。采用自动管电流调制（ATCM）并使用各种质量参考毫安秒（150、200、250和300）应用腹部扫描方案（n = 12）。每次毫安秒选择使用的千伏值为100、120和140。金属氧化物半导体场效应晶体管剂量计（MOSFET）测量内部器官剂量。所有产生的图像均采用滤波反投影（FBP）和正弦图确认迭代重建（SAFIRE）（3、4和5）进行重建，并在L4-L5水平的三个感兴趣区域内测量客观噪声。器官剂量从0.12至41.9毫戈瑞不等，两种模型尺寸中脾脏接受的剂量最高。与模拟平均体型的模型相比，肥胖模型在匹配的毫安秒选择下，所递送的毫安秒、剂量长度乘积（DLP）和计算机断层扫描剂量指数（CTDIvol）增加了两倍（p < 0.05）。然而，器官剂量仅增加了50%。与120 kV相比，使用100 kV可使剂量降低40%（p < 0.05），并且使用SAFIRE（5）改善了相关的噪声增加，与FBP相比，噪声降低了60%（p < 0.05）。当与迭代重建相结合时，低千伏对肥胖患者优化辐射剂量并维持客观图像质量是可行的。
