D'Hondt Aurélie, Cornil A, Bohy P, De Maertelaer V, Gevenois P A, Tack D
Department of Radiology, Hôpital Erasme, Brussels, Belgium.
Br J Radiol. 2014 May;87(1037):20130707. doi: 10.1259/bjr.20130707. Epub 2014 Mar 10.
To investigate the impact of tuning the automatic exposure control (AEC) strength curve (specific to Care Dose 4D®; Siemens Healthcare, Forchheim, Germany) from "average" to "strong" on image quality, radiation dose and operator dependency during lumbar spine CT examinations.
Two hospitals (H1, H2), both using the same scanners, were considered for two time periods (P1 and P2). During P1, the AEC curve was "average" and radiographers had to select one of two protocols according to the body mass index (BMI): "standard" if BMI <30.0 kg m(-2) (120 kV-330 mAs) or "large" if BMI >30.0 kg m(-2) (140 kV-280 mAs). During P2, the AEC curve was changed to "strong", and all acquisitions were obtained with one protocol (120 kV and 270 mAs). Image quality was scored and patients' diameters calculated for both periods.
497 examinations were analysed. There was no significant difference in mean diameters according to hospitals and periods (p > 0.801) and in quality scores between periods (p > 0.172). There was a significant difference between hospitals regarding how often the "large" protocol was assigned [13 (10%)/132 patients in H1 vs 37 (28%)/133 in H2] (p < 0.001). During P1, volume CT dose index (CTDIvol) was higher in H2 (+13%; p = 0.050). In both hospitals, CTDIvol was reduced between periods (-19.2% in H1 and -29.4% in H2; p < 0.001).
An operator dependency in protocol selection, unexplained by patient diameters or highlighted by image quality scores, has been observed. Tuning the AEC curve from average to strong enables suppression of the operator dependency in protocol selection and related dose increase, while preserving image quality.
CT acquisition protocols based on weight are responsible for biases in protocol selection. Using an appropriate AEC strength curve reduces the number of protocols to one. Operator dependency of protocol selection is thereby eliminated.
探讨在腰椎CT检查中，将自动曝光控制（AEC）强度曲线（特定于Care Dose 4D®；德国福希海姆西门子医疗公司）从“平均”调整为“强”对图像质量、辐射剂量和操作者依赖性的影响。
考虑两家使用相同扫描仪的医院（H1、H2），分两个时间段（P1和P2）进行研究。在P1期间，AEC曲线为“平均”，放射技师必须根据体重指数（BMI）选择两种方案之一：如果BMI＜30.0 kg·m⁻²，则选择“标准”方案（120 kV - 330 mAs）；如果BMI＞30.0 kg·m⁻²，则选择“大剂量”方案（140 kV - 280 mAs）。在P2期间，AEC曲线改为“强”，所有扫描均采用一种方案（120 kV和270 mAs）。对两个时间段的图像质量进行评分，并计算患者的直径。
共分析了497例检查。根据医院和时间段，平均直径无显著差异（p＞0.801），时间段之间的质量评分也无显著差异（p＞0.172）。两家医院在分配“大剂量”方案的频率上存在显著差异[H1为13例（10%）/132例患者，H2为37例（28%）/133例患者]（p＜0.001）。在P1期间，H2的容积CT剂量指数（CTDIvol）较高（+13%；p = 0.050）。在两家医院中，时间段之间CTDIvol均有所降低（H1降低19.2%，H2降低29.4%；p＜0.001）。
观察到在方案选择中存在操作者依赖性，这无法用患者直径来解释，也未在图像质量评分中体现。将AEC曲线从平均调整为强可抑制方案选择中的操作者依赖性以及相关的剂量增加，同时保持图像质量。
基于体重的CT扫描方案会导致方案选择中的偏差。使用适当的AEC强度曲线可将方案数量减少至一个。从而消除了方案选择中的操作者依赖性。
