Department of Diagnostic Imaging, Warren Alpert Medical School of Brown University, Rhode Island Hospital, 593 Eddy St, Providence, RI 02903, USA.
Radiology. 2013 Mar;266(3):791-800. doi: 10.1148/radiol.12120134. Epub 2012 Dec 21.
To assess the effect of a decrease in tube voltage from 120 kVp to 100 kVp on dose, contrast-to-noise ratio (CNR), and three-dimensional (3D) image quality in patients undergoing computed tomographic (CT) colonography as well as to determine how these changes are affected by patient size.
This HIPAA-compliant and institutional review board-approved retrospective study included 63 consecutive patients who underwent CT colonography and who waived informed consent. Scanning was performed with patients in the supine (120 kVp) and prone (100 kVp) positions, with other parameters unchanged. Volume CT dose index (CTDI(vol)), dose-length product (DLP), image noise, attenuation of selected materials, and CNR were compared with the Wilcoxon matched-pairs signed rank test. Two readers blinded to tube voltage independently assessed 3D endoluminal image quality. The k coefficients were calculated for interobserver agreement. Average image quality ratings were compared with the Wilcoxon signed rank test. All recorded data were stratified by patient anteroposterior diameter to determine effects of patient size.
Decreasing tube voltage from 120 to 100 kVp resulted in a 20% decrease in CTDI(vol) (P < .001) and a 16% decrease in DLP (P < .001). Image noise increased by 32% (P < .001). Mean attenuation of tagged fluid increased from 395 to 487 HU (P < .001). There was no change in mean CNR of tagged fluid (17.1 at 120 kVp, 16.8 at 100 kVp; P = .37), regardless of patient size. The 3D image quality decreased slightly from a median score of 5 out of 5 to 4 out of 5 (P < .001). There was substantial interobserver agreement.
A decrease in tube voltage from 120 to 100 kVp results in a significant decrease in radiation dose but only a minimal decrease in 3D image quality at all patient sizes. © RSNA, 2012.
评估管电压从 120kVp 降至 100kVp 对行 CT 结肠成像患者的剂量、对比噪声比（CNR）和三维（3D）图像质量的影响，并确定这些变化如何受患者体型的影响。
这项符合 HIPAA 标准和机构审查委员会批准的回顾性研究纳入了 63 例连续行 CT 结肠成像且放弃知情同意的患者。患者分别在仰卧位（120kVp）和俯卧位（100kVp）进行扫描，其他参数不变。使用 Wilcoxon 配对符号秩检验比较容积 CT 剂量指数（CTDI（vol））、剂量长度乘积（DLP）、图像噪声、选定材料的衰减和 CNR。两名对管电压不知情的观察者独立评估 3D 腔内图像质量。计算观察者间一致性的 k 系数。使用 Wilcoxon 符号秩检验比较平均图像质量评分。根据患者前后径将所有记录数据分层，以确定患者体型的影响。
管电压从 120kVp 降至 100kVp 导致 CTDI（vol）降低 20%（P＜.001），DLP 降低 16%（P＜.001）。图像噪声增加 32%（P＜.001）。标记液的平均衰减从 395HU 增加至 487HU（P＜.001）。标记液的平均 CNR 无变化（120kVp 时为 17.1，100kVp 时为 16.8；P＝.37），与患者体型无关。3D 图像质量从 5 分（满分 5 分）略有下降至 4 分（P＜.001）。观察者间一致性较好。
管电压从 120kVp 降至 100kVp 可显著降低辐射剂量，但在所有患者体型中，3D 图像质量仅略有下降。©RSNA，2012。
