低剂量CT结合迭代模型重建算法用于恶性肿瘤治疗后患者反应评估时的图像质量改善
Improved image quality of low-dose CT combining with iterative model reconstruction algorithm for response assessment in patients after treatment of malignant tumor.
作者信息
Xin Xiaoyan, Shen Jingtao, Yang Shangwen, Liu Song, Hu Anning, Zhu Bin, Jiang Yan, Li Baoxin, Zhang Bing
机构信息
Department of Radiology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing 210008, China.
Department of Nuclear Medicine, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing 210008, China.
出版信息
Quant Imaging Med Surg. 2018 Aug;8(7):648-657. doi: 10.21037/qims.2018.08.05.
BACKGROUND
To evaluate the image quality and radiation dose of low-dose (LD) computed tomography (LD-CT) combining with iterative model reconstruction (IMR) algorithm for response assessment in patients after treatment of malignant tumor compared with routine-dose CT (RD-CT).
METHODS
Forty-seven patients [mean age 57.8±10.9 years, 30 males, body mass index (BMI) 22.09±2.35 kg/m] after treatment of malignant tumor underwent contrast-enhanced chest and abdomen CT twice for response assessment with an interval of 6 months according to clinical routine. The first CT scans were performed with RD protocol at 120 kVp and images were reconstructed with filtered back projection (FBP) algorithm; while the second scans were performed with LD protocol at 100 kVp and images were reconstructed with FBP and IMR algorithm respectively. All scans were performed using an automatic tube current modulation technique with 150 mAs as reference. Objective image quality including CT attenuation, image noise, and contrast to noise ratio (CNR), and subjective image quality including artifacts, noise, visualization of small structures and confidence of targeted lesions, as well as lesion detection were assessed and compared.
RESULTS
Effective radiation dose of LD-CT scans was reduced 54.8% compared to RD-CT scans (26.89±3.35 12.14±2.09 mSv). Higher CT attenuation was found in both LD-IMR and LD-FBP images compared to RD-FBP images. Better subjective image quality and CNR as well as lower objective noise were found in LD-IMR images (all, P<0.05). Two small lesions with the diameter less than 1 cm were missed in LD-FBP images, which were able to be observed in LD-IMR images.
CONCLUSIONS
IMR is able to help more than half of reduction of radiation dose without compromising the quality of diagnostic information in patients after treatment of malignant tumors to chest and abdomen CT for response assessment.
背景
评估低剂量（LD）计算机断层扫描（LD-CT）联合迭代模型重建（IMR）算法用于恶性肿瘤治疗后患者疗效评估的图像质量和辐射剂量，并与常规剂量CT（RD-CT）进行比较。
方法
47例恶性肿瘤治疗后的患者[平均年龄57.8±10.9岁，男性30例，体重指数（BMI）22.09±2.35kg/m²]，按照临床常规，间隔6个月接受两次胸部和腹部增强CT扫描以进行疗效评估。第一次CT扫描采用120kVp的RD协议，并使用滤波反投影（FBP）算法重建图像；而第二次扫描采用100kVp的LD协议，并分别使用FBP和IMR算法重建图像。所有扫描均采用自动管电流调制技术，以150mAs作为参考。评估并比较包括CT衰减、图像噪声和对比噪声比（CNR）在内的客观图像质量，以及包括伪影、噪声、小结构可视化和目标病变置信度在内的主观图像质量，以及病变检测情况。
结果
与RD-CT扫描相比，LD-CT扫描的有效辐射剂量降低了54.8%（26.89±3.35对12.14±2.09mSv）。与RD-FBP图像相比，LD-IMR和LD-FBP图像中的CT衰减更高。LD-IMR图像的主观图像质量和CNR更好，客观噪声更低（均P<0.05）。LD-FBP图像中漏诊了2个直径小于1cm的小病变，而在LD-IMR图像中能够观察到。
结论
对于接受胸部和腹部CT进行疗效评估的恶性肿瘤治疗后患者，IMR能够在不影响诊断信息质量的情况下，帮助将辐射剂量降低一半以上。
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