From the Department of Radiological Sciences, St Jude Children's Research Hospital, 262 Danny Thomas Pl, Memphis, TN 38139.
Radiology. 2014 Jan;270(1):223-31. doi: 10.1148/radiol.13122578. Epub 2013 Oct 28.
To determine a comprehensive method for the implementation of adaptive statistical iterative reconstruction (ASIR) for maximal radiation dose reduction in pediatric computed tomography (CT) without changing the magnitude of noise in the reconstructed image or the contrast-to-noise ratio (CNR) in the patient.
The institutional review board waived the need to obtain informed consent for this HIPAA-compliant quality analysis. Chest and abdominopelvic CT images obtained before ASIR implementation (183 patient examinations; mean patient age, 8.8 years ± 6.2 [standard deviation]; range, 1 month to 27 years) were analyzed for image noise and CNR. These measurements were used in conjunction with noise models derived from anthropomorphic phantoms to establish new beam current-modulated CT parameters to implement 40% ASIR at 120 and 100 kVp without changing noise texture or magnitude. Image noise was assessed in images obtained after ASIR implementation (492 patient examinations; mean patient age, 7.6 years ± 5.4; range, 2 months to 28 years) the same way it was assessed in the pre-ASIR analysis. Dose reduction was determined by comparing size-specific dose estimates in the pre- and post-ASIR patient cohorts. Data were analyzed with paired t tests.
With 40% ASIR implementation, the average relative dose reduction for chest CT was 39% (2.7/4.4 mGy), with a maximum reduction of 72% (5.3/18.8 mGy). The average relative dose reduction for abdominopelvic CT was 29% (4.8/6.8 mGy), with a maximum reduction of 64% (7.6/20.9 mGy). Beam current modulation was unnecessary for patients weighing 40 kg or less. The difference between 0% and 40% ASIR noise magnitude was less than 1 HU, with statistically nonsignificant increases in patient CNR at 100 kVp of 8% (15.3/14.2; P = .41) for chest CT and 13% (7.8/6.8; P = .40) for abdominopelvic CT.
Radiation dose reduction at pediatric CT was achieved when 40% ASIR was implemented as a dose reduction tool only; no net change to the magnitude of noise in the reconstructed image or the patient CNR occurred.
确定一种综合方法，在不改变重建图像噪声幅度或患者对比噪声比（CNR）的情况下，在儿科计算机断层扫描（CT）中实现自适应统计迭代重建（ASIR）以最大程度地降低辐射剂量。
本机构审查委员会豁免了这项符合 HIPAA 规定的质量分析获得知情同意的要求。对实施 ASIR 之前（183 例患者检查；平均患者年龄 8.8 岁±6.2[标准差]；范围 1 个月至 27 岁）的胸部和腹部盆腔 CT 图像进行噪声和 CNR 分析。这些测量结果与源自人体模型的噪声模型结合使用，建立了新的管电流调制 CT 参数，以在 120 和 100 kVp 下实现 40%的 ASIR，而不改变噪声纹理或幅度。在实施 ASIR 后（492 例患者检查；平均患者年龄 7.6 岁±5.4；范围 2 个月至 28 岁）获得的图像中，以与预 ASIR 分析相同的方式评估图像噪声。通过比较预 ASIR 和后 ASIR 患者队列中的大小特异性剂量估计值来确定剂量减少。使用配对 t 检验对数据进行分析。
实施 40%ASIR 后，胸部 CT 的平均相对剂量减少 39%（2.7/4.4 mGy），最大减少 72%（5.3/18.8 mGy）。腹部盆腔 CT 的平均相对剂量减少 29%（4.8/6.8 mGy），最大减少 64%（7.6/20.9 mGy）。体重 40kg 或以下的患者不需要管电流调制。0%和 40%ASIR 噪声幅度之间的差异小于 1HU，在 100kVp 时患者 CNR 统计学上无显著增加，胸部 CT 为 8%（15.3/14.2；P=0.41），腹部盆腔 CT 为 13%（7.8/6.8；P=0.40）。
仅将 40%ASIR 作为剂量减少工具实施时，在儿科 CT 中实现了辐射剂量减少，而重建图像噪声幅度或患者 CNR 没有发生净变化。
