Institute for Diagnostic and Interventional Neuroradiology, University of Berne, Switzerland.
AJNR Am J Neuroradiol. 2011 Sep;32(8):1375-80. doi: 10.3174/ajnr.A2524. Epub 2011 Jul 14.
The temporal bone is ideal for low-dose CT because of its intrinsic high contrast. The aim of this study was to retrospectively evaluate image quality and radiation doses of a new low-dose versus a standard high-dose pediatric temporal bone CT protocol and to review dosimetric data from the literature.
Image quality and radiation doses were compared for 38 low-dose (80 kV/90-110 mAs) and 16 high-dose (140 kV/170 mAs) temporal bone CT scans of infants to 5-year-old children. The CT visualization quality of 23 middle and inner ear structures was subjectively graded by 3 neuroradiologists and 3 otologists by using a 5-point scale with scores 1-2 indicating insufficient and scores 3-5 indicating sufficient image quality. Effective doses of local and literature-derived protocols were calculated from dosimetric data by using NRPB-SR250 software.
Insufficient image-quality scores were more frequent in low-dose scans versus high-dose scans, but the difference was only statistically significant for otologists (6.0% versus 3.4%, P = .004) and not for neuroradiologists (1.2% versus 0.7%, P = .84). Image quality was critical for small structures (such as the stapes or lamella at the internal auditory canal fundus). Effective doses were 0.25-0.3 mSv for low-dose scans, 1.4-1.8 mSv for high-dose scans, and 0.9-2.6 mSv for literature-derived protocols.
The image quality of the new low-dose protocol remains diagnostic for assessing middle and inner ear anatomy despite a 3- to 8-fold dose reduction over previous and literature-derived protocols. However, image quality of small structures is critical and may be perceived as insufficient.
由于其固有对比度高,颞骨非常适合进行低剂量 CT 检查。本研究旨在回顾性评估新的低剂量与标准高剂量儿童颞骨 CT 方案的图像质量和辐射剂量,并回顾文献中的剂量学数据。
对 38 例婴儿至 5 岁儿童的低剂量(80kV/90-110mAs)和 16 例高剂量(140kV/170mAs)颞骨 CT 扫描进行了图像质量和辐射剂量比较。3 名神经放射学家和 3 名耳科医生使用 5 分制对 23 个中耳和内耳结构的 CT 可视化质量进行了主观评分,评分 1-2 表示图像质量不足,评分 3-5 表示图像质量充足。通过 NRPB-SR250 软件使用剂量学数据计算局部和文献衍生方案的有效剂量。
低剂量扫描的图像质量评分不足的情况比高剂量扫描更为常见,但只有耳科医生的差异具有统计学意义(6.0%对 3.4%,P=.004),而神经放射医生的差异无统计学意义(1.2%对 0.7%,P=.84)。对于小结构(如镫骨或内耳道底部的板层),图像质量至关重要。低剂量扫描的有效剂量为 0.25-0.3mSv,高剂量扫描的有效剂量为 1.4-1.8mSv,文献衍生方案的有效剂量为 0.9-2.6mSv。
尽管与之前和文献衍生的方案相比,剂量降低了 3-8 倍,但新的低剂量方案的图像质量仍可用于评估中耳和内耳解剖结构,保持诊断性。然而,小结构的图像质量至关重要,可能被认为是不足的。