Department of Radiology, Duke University Medical Center, Erwin Road, Durham, NC, 27710, USA.
Radiology. 2010 Jan;254(1):145-53. doi: 10.1148/radiol.09090094.
To investigate whether an adaptive statistical iterative reconstruction (ASIR) algorithm improves the image quality at low-tube-voltage (80-kVp), high-tube-current (675-mA) multidetector abdominal computed tomography (CT) during the late hepatic arterial phase.
This prospective, single-center HIPAA-compliant study was institutional review board approved. Informed patient consent was obtained. Ten patients (six men, four women; mean age, 63 years; age range, 51-77 years) known or suspected to have hypervascular liver tumors underwent dual-energy 64-section multidetector CT. High- and low-tube-voltage CT images were acquired sequentially during the late hepatic arterial phase of contrast enhancement. Standard convolution FBP was used to reconstruct 140-kVp (protocol A) and 80-kVp (protocol B) image sets, and ASIR (protocol C) was used to reconstruct 80-kVp image sets. The mean image noise; contrast-to-noise ratio (CNR) relative to muscle for the aorta, liver, and pancreas; and effective dose with each protocol were assessed. A figure of merit (FOM) was computed to normalize the image noise and CNR for each protocol to effective dose. Repeated-measures analysis of variance with Bonferroni adjustment for multiple comparisons was used to compare differences in mean CNR, image noise, and corresponding FOM among the three protocols. The noise power spectra generated from a custom phantom with each protocol were also compared.
When image noise was normalized to effective dose, protocol C, as compared with protocols A (P = .0002) and B (P = .0001), yielded an approximately twofold reduction in noise. When the CNR was normalized to effective dose, protocol C yielded significantly higher CNRs for the aorta, liver, and pancreas than did protocol A (P = .0001 for all comparisons) and a significantly higher CNR for the liver than did protocol B (P = .003). Mean effective doses were 17.5 mSv +/- 0.6 (standard error) with protocol A and 5.1 mSv +/- 0.3 with protocols B and C. Compared with protocols A and B, protocol C yielded a small but quantifiable noise reduction across the entire spectrum of spatial frequencies.
Compared with standard FBP reconstruction, an ASIR algorithm improves image quality and has the potential to decrease radiation dose at low-tube-voltage, high-tube-current multidetector abdominal CT during the late hepatic arterial phase.
探讨自适应统计迭代重建（ASIR）算法是否能提高低管电压（80kVp）、高管电流（675mA）多层螺旋腹部 CT 肝期晚期的图像质量。
本研究为前瞻性、单中心、符合 HIPAA 标准的研究，得到了机构审查委员会的批准。患者均签署了知情同意书。10 例（6 例男性，4 例女性；平均年龄 63 岁；年龄范围 51-77 岁）已知或疑似有富血管性肝肿瘤的患者接受了双能 64 层螺旋 CT 检查。在对比增强的肝期晚期，依次采集高、低管电压 CT 图像。使用标准卷积滤波反投影（FBP）分别对 140kVp（方案 A）和 80kVp（方案 B）图像进行重建，对 80kVp 图像使用 ASIR（方案 C）进行重建。评估每个方案的平均图像噪声、相对于肌肉的主动脉、肝脏和胰腺的对比噪声比（CNR），以及有效剂量。计算每个方案的质量因子（FOM），将图像噪声和 CNR 标准化到每个方案的有效剂量。采用重复测量方差分析和 Bonferroni 多重比较检验，比较三种方案间的平均 CNR、图像噪声和相应的 FOM 差异。还比较了每个方案下使用定制体模生成的噪声功率谱。
当图像噪声标准化到有效剂量时，与方案 A（P=.0002）和方案 B（P=.0001）相比，方案 C 可使噪声降低约两倍。当 CNR 标准化到有效剂量时，方案 C 对主动脉、肝脏和胰腺的 CNR 显著高于方案 A（所有比较均为 P=.0001），对肝脏的 CNR 显著高于方案 B（P=.003）。方案 A 的平均有效剂量为 17.5mSv +/- 0.6（标准误差），方案 B 和 C 的平均有效剂量为 5.1mSv +/- 0.3。与方案 A 和 B 相比，方案 C 在整个空间频率谱上都有较小但可量化的噪声降低。
与标准 FBP 重建相比，ASIR 算法可提高图像质量，并有可能降低低管电压、高管电流多层螺旋腹部 CT 肝期晚期的辐射剂量。
