From the Departments of Medical Imaging (R.N.S., D.M.E.B., M.A.T., R.A.A., C.A.M.)
From the Departments of Medical Imaging (R.N.S., D.M.E.B., M.A.T., R.A.A., C.A.M.).
AJNR Am J Neuroradiol. 2019 May;40(5):866-871. doi: 10.3174/ajnr.A6034. Epub 2019 Apr 11.
Noncontrast CT of the head is the initial imaging test for traumatic brain injury, stroke, or suspected nonaccidental trauma. Low-dose head CT protocols using filtered back-projection are susceptible to increased noise and decreased image quality. Iterative reconstruction noise suppression allows the use of lower-dose techniques with maintained image quality. We review our experience with children undergoing emergency head CT examinations reconstructed using knowledge-based iterative model reconstruction versus standard filtered back-projection, comparing reconstruction times, radiation dose, and objective and subjective image quality.
This was a retrospective study comparing 173 children scanned using standard age-based noncontrast head CT protocols reconstructed with filtered back-projection with 190 children scanned using low-dose protocols reconstructed with iterative model reconstruction. ROIs placed on the frontal white matter and thalamus yielded signal-to-noise and contrast-to-noise ratios. Volume CT dose index and study reconstruction times were recorded. Random subgroups of patients were selected for subjective image-quality review.
The volume CT dose index was significantly reduced in studies reconstructed with iterative model reconstruction compared with filtered back-projection, (mean, 24.4 ± 3.1 mGy versus 31.1 ± 6.0 mGy, < .001), while the SNR and contrast-to-noise ratios improved 2-fold ( < .001). Radiologists graded iterative model reconstruction images as superior to filtered back-projection images for gray-white matter differentiation and anatomic detail ( < .001). The average reconstruction time of the filtered back-projection studies was 101 seconds, and with iterative model reconstruction, it was 147 seconds ( < .001), without a practical effect on work flow.
In children referred for emergency noncontrast head CT, optimized low-dose protocols with iterative model reconstruction allowed us to significantly reduce the relative dose, on average, 22% compared with filtered back-projection, with significantly improved objective and subjective image quality.
头部非增强 CT 是创伤性脑损伤、中风或疑似非外伤性创伤的初始影像学检查。使用滤波反投影的低剂量头部 CT 方案容易出现噪声增加和图像质量下降。迭代重建噪声抑制允许使用保持图像质量的更低剂量技术。我们回顾了使用基于知识的迭代模型重建与标准滤波反投影对行急诊头部 CT 检查的儿童的经验，比较了重建时间、辐射剂量以及客观和主观的图像质量。
这是一项回顾性研究，比较了 173 名使用标准年龄相关非增强头部 CT 方案扫描并使用滤波反投影重建的儿童与 190 名使用迭代模型重建的低剂量方案扫描的儿童。在额白质和丘脑上放置 ROI 以获得信噪比和对比噪声比。记录容积 CT 剂量指数和研究重建时间。随机选择患者的子组进行主观图像质量评估。
与滤波反投影相比，使用迭代模型重建的研究中容积 CT 剂量指数显著降低（平均值分别为 24.4 ± 3.1 mGy 和 31.1 ± 6.0 mGy， <.001），而 SNR 和对比噪声比提高了 2 倍（ <.001）。放射科医生将迭代模型重建的图像评为优于滤波反投影的图像，在灰度-白质区分和解剖细节方面（ <.001）。滤波反投影研究的平均重建时间为 101 秒，而迭代模型重建的重建时间为 147 秒（ <.001），但对工作流程没有实际影响。
在因急诊非增强头部 CT 而就诊的儿童中，与滤波反投影相比，使用迭代模型重建的优化低剂量方案可使相对剂量显著降低，平均降低 22%，同时显著提高客观和主观的图像质量。
