Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Songpa-gu, Seoul, Korea.
AJR Am J Roentgenol. 2011 Jul;197(1):50-7. doi: 10.2214/AJR.11.6582.
The purpose of this study was to prospectively compare standard-dose CT enterography (CTE) and 50% reduced-dose CTE, obtained with and without an image noise reduction method, in the evaluation of Crohn disease.
Ninety-two patients (69 men and 23 women; mean age [± SD], 31.2 ± 9.5 years) with Crohn disease underwent CTE. Using a dual-source scanner equipped with a proprietary noise reduction method (iterative reconstruction in image space [IRIS]), three sets of CTE images were obtained: standard-dose filtered back projection (FBP) (i.e., weighted FBP), low-dose (i.e., 50% reduction) FBP, and low-dose IRIS CTE. Image noise was measured. Two independent radiologists evaluated subjective image quality (1 [worst] to 4 [best]) and findings of active Crohn disease in the terminal small-bowel segment, including mural hyperenhancement, thickening and stratification, comb sign, and increased perienteric fat attenuation (1 [definitely absent] to 5 [definitely present]).
The mean (± SD) volume CT dose index (CTDI(vol)) was 7.0 ± 0.9 mGy and 3.5 ± 0.5 mGy for standard-dose and low-dose CTE examinations, respectively. The mean (± SD) image noise for standard-dose FBP, low-dose FBP, and low-dose IRIS CTE was 10.6 ± 1.7 HU, 13.9 ± 2.1 HU, and 9.7 ± 1.7 HU, respectively (p < 0.001 for all comparisons). Both assessors found that image quality was poorer with low-dose (mean grade (± SD), 2.3 ± 0.4-2.7 ± 0.5) than in standard-dose (3 ± 0) CTE (p < 0.01), and one found that image quality was poorer with low-dose IRIS (2.3 ± 0.4) than with low-dose FBP (2.7 ± 0.5) CTE (p < 0.01). Low-dose (with or without IRIS) and standard-dose CTE showed ≥ 85% agreement (one-sided 95% CI ≥ 77%) in interpretation of bowel findings.
Low-dose CTE using 50% reduced-dose performed similarly to standard-dose CTE in identifying findings of enteric inflammation of Crohn disease. Although a noise reduction method markedly reduced image noise in half-dose examinations, its effect on image quality was not as great and was reader dependent.
本研究旨在前瞻性比较标准剂量 CT 肠造影（CTE）和 50%降低剂量 CTE，包括和不包括图像降噪方法，用于评估克罗恩病。
92 例（69 名男性和 23 名女性；平均年龄[±标准差]，31.2±9.5 岁）克罗恩病患者行 CTE 检查。使用配备专有降噪方法（迭代重建图像空间[IRIS]）的双源扫描仪，获得三组 CTE 图像：标准剂量滤波反投影（FBP）（即加权 FBP）、低剂量（即 50%降低）FBP 和低剂量 IRIS CTE。测量图像噪声。两名独立的放射科医生评估主观图像质量（1[最差]至 4[最佳]）和终端小肠段活动性克罗恩病的发现，包括壁层强化、增厚和分层、梳状征和增加的肠周脂肪衰减（1[肯定不存在]至 5[肯定存在]）。
标准剂量和低剂量 CTE 检查的平均（±标准差）容积 CT 剂量指数（CTDI(vol)）分别为 7.0±0.9 mGy 和 3.5±0.5 mGy。标准剂量 FBP、低剂量 FBP 和低剂量 IRIS CTE 的平均（±标准差）图像噪声分别为 10.6±1.7 HU、13.9±2.1 HU 和 9.7±1.7 HU（所有比较均 p<0.001）。两位评估者均发现低剂量（平均等级（±标准差），2.3±0.4-2.7±0.5）比标准剂量（3±0）CTE 的图像质量更差（p<0.01），一位评估者发现低剂量 IRIS（2.3±0.4）比低剂量 FBP（2.7±0.5）CTE 的图像质量更差（p<0.01）。低剂量（带或不带 IRIS）和标准剂量 CTE 在解释肠腔发现方面具有≥85%的一致性（单侧 95%CI≥77%）。
使用 50%降低剂量的低剂量 CTE 在识别克罗恩病肠炎症发现方面与标准剂量 CTE 相似。尽管降噪方法使半剂量检查中的图像噪声降低了约一半，但对图像质量的影响并没有那么大，而且还取决于读者。
