Parikh Roshni A, Wien Michael A, Novak Ronald D, Jordan David W, Klahr Paul, Soriano Stephanie, Ciancibello Leslie, Berlin Sheila C
Department of Radiology, Rainbow Babies and Children's Hospital, University Hospitals Cleveland Medical Center, Case Western Reserve University School of Medicine, 11100 Euclid Ave., Cleveland, OH, 44106, USA.
Department of Radiology, University of Michigan Health System, Ann Arbor, MI, USA.
Pediatr Radiol. 2018 Jan;48(1):56-65. doi: 10.1007/s00247-017-3986-7. Epub 2017 Sep 27.
The size-specific dose estimate (SSDE) has emerged as an improved metric for use by medical physicists and radiologists for estimating individual patient dose. Several methods of calculating SSDE have been described, ranging from patient thickness or attenuation-based (automated and manual) measurements to weight-based techniques.
To compare the accuracy of thickness vs. weight measurement of body size to allow for the calculation of the size-specific dose estimate (SSDE) in pediatric body CT.
We retrospectively identified 109 pediatric body CT examinations for SSDE calculation. We examined two automated methods measuring a series of level-specific diameters of the patient's body: method A used the effective diameter and method B used the water-equivalent diameter. Two manual methods measured patient diameter at two predetermined levels: the superior endplate of L2, where body width is typically most thin, and the superior femoral head or iliac crest (for scans that did not include the pelvis), where body width is typically most thick; method C averaged lateral measurements at these two levels from the CT projection scan, and method D averaged lateral and anteroposterior measurements at the same two levels from the axial CT images. Finally, we used body weight to characterize patient size, method E, and compared this with the various other measurement methods. Methods were compared across the entire population as well as by subgroup based on body width.
Concordance correlation (ρ) between each of the SSDE calculation methods (methods A-E) was greater than 0.92 across the entire population, although the range was wider when analyzed by subgroup (0.42-0.99). When we compared each SSDE measurement method with CTDI there was poor correlation, ρ<0.77, with percentage differences between 20.8% and 51.0%.
Automated computer algorithms are accurate and efficient in the calculation of SSDE. Manual methods based on patient thickness provide acceptable dose estimates for pediatric patients <30 cm in body width. Body weight provides a quick and practical method to identify conversion factors that can be used to estimate SSDE with reasonable accuracy in pediatric patients with body width ≥20 cm.
特定尺寸剂量估算（SSDE）已成为医学物理师和放射科医生用于估算个体患者剂量的一种改进指标。已经描述了几种计算SSDE的方法，从基于患者厚度或衰减的（自动和手动）测量到基于体重的技术。
比较身体尺寸的厚度测量与体重测量的准确性，以计算儿科身体CT中的特定尺寸剂量估算（SSDE）。
我们回顾性地确定了109例用于SSDE计算的儿科身体CT检查。我们研究了两种测量患者身体一系列特定层面直径的自动方法：方法A使用有效直径，方法B使用水等效直径。两种手动方法在两个预定层面测量患者直径：L2的上终板，此处身体宽度通常最窄，以及股骨头或髂嵴上方（对于不包括骨盆的扫描），此处身体宽度通常最宽；方法C从CT投影扫描中对这两个层面的横向测量值求平均值，方法D从轴向CT图像中对相同两个层面的横向和前后测量值求平均值。最后，我们使用体重来表征患者尺寸，即方法E，并将其与其他各种测量方法进行比较。在整个人群以及根据身体宽度划分出的亚组中对各种方法进行了比较。
在整个人群中，每种SSDE计算方法（方法A - E）之间的一致性相关性（ρ）均大于0.92，尽管按亚组分析时范围更宽（0.42 - 0.99）。当我们将每种SSDE测量方法与CTDI进行比较时，相关性较差，ρ<0.77，百分比差异在20.8%至51.0%之间。
自动计算机算法在计算SSDE方面准确且高效。基于患者厚度的手动方法可为身体宽度<30 cm的儿科患者提供可接受的剂量估算。体重提供了一种快速实用的方法来确定转换因子，可用于以合理的准确性估算身体宽度≥20 cm的儿科患者的SSDE。
