Björkdahl Peter, Nyman Ulf
Department of Radiology, University of Lund, Lasarettet Trelleborg, Trelleborg, Sweden.
Acta Radiol. 2010 Apr;51(3):260-70. doi: 10.3109/02841850903505222.
Concern has been raised regarding the mounting collective radiation doses from computed tomography (CT), increasing the risk of radiation-induced cancers in exposed populations.
To compare radiation dose and image quality in a chest phantom and in patients for the diagnosis of pulmonary embolism (PE) at 100 and 120 peak kilovoltage (kVp) using 16-multichannel detector computed tomography (MDCT).
A 20-ml syringe containing 12 mg I/ml was scanned in a chest phantom at 100/120 kVp and 25 milliampere seconds (mAs). Consecutive patients underwent 100 kVp (n = 50) and 120 kVp (n = 50) 16-MDCT using a "quality reference" effective mAs of 100, 300 mg I/kg, and a 12-s injection duration. Attenuation (CT number), image noise (1 standard deviation), and contrast-to-noise ratio (CNR; fresh clot = 70 HU) of the contrast medium syringe and pulmonary arteries were evaluated on 3-mm-thick slices. Subjective image quality was assessed. Computed tomography dose index (CTDI(vol)) and dose-length product (DLP) were presented by the CT software, and effective dose was estimated.
Mean values in the chest phantom and patients changed as follows when X-ray tube potential decreased from 120 to 100 kVp: attenuation +23% and +40%, noise +38% and +48%, CNR -6% and 0%, and CTDI(vol) -38% and -40%, respectively. Mean DLP and effective dose in the patients decreased by 42% and 45%, respectively. Subjective image quality was excellent or adequate in 49/48 patients at 100/120 kVp. No patient with a negative CT had any thromboembolism diagnosed during 3-month follow-up.
By reducing X-ray tube potential from 120 to 100 kVp, while keeping all other scanning parameters unchanged, the radiation dose to the patient may be almost halved without deterioration of diagnostic quality, which may be of particular benefit in young individuals.
人们对计算机断层扫描（CT）累积的集体辐射剂量不断增加表示担忧，这增加了受照人群中辐射诱发癌症的风险。
使用16通道探测器计算机断层扫描（MDCT），比较胸部体模和患者在100和120千伏峰值电压（kVp）下诊断肺栓塞（PE）时的辐射剂量和图像质量。
将一支装有12毫克碘/毫升的20毫升注射器在胸部体模中于100/120 kVp和25毫安秒（mAs）条件下进行扫描。连续的患者接受100 kVp（n = 50）和120 kVp（n = 50）的16层MDCT扫描，使用“质量参考”有效mAs为100、300毫克碘/千克，注射持续时间为12秒。在3毫米厚的层面上评估造影剂注射器和肺动脉的衰减（CT值）、图像噪声（1个标准差）以及对比噪声比（CNR；新鲜血栓 = 70 HU）。对主观图像质量进行评估。CT软件给出计算机断层扫描剂量指数（CTDI(vol)）和剂量长度乘积（DLP），并估算有效剂量。
当X射线管电压从120 kVp降至100 kVp时，胸部体模和患者中的平均值变化如下：衰减分别增加23%和40%，噪声分别增加38%和48%，CNR分别降低6%和0%，CTDI(vol)分别降低38%和40%。患者中的平均DLP和有效剂量分别降低了42%和45%。在100/120 kVp时，49/48例患者的主观图像质量为优或良好。在3个月的随访期间，CT检查结果为阴性的患者均未诊断出任何血栓栓塞。
在保持所有其他扫描参数不变的情况下，将X射线管电压从120 kVp降至100 kVp，患者所接受的辐射剂量可几乎减半，且诊断质量不会下降，这对年轻人可能特别有益。
