摘要
目的通过模型实验证实低剂量CT肺动脉成像（CTPA）的可能性并筛选出合理低剂量阈值。方法测量132例患者气管内、体外空气密度差，制成噪声测量和肺动脉栓塞（PE）模型。设置管电压为120kVp，管电流分别为280、200、160、100、90、80、70、60、50、40、30、20、15、10mA，扫描上述两种模型和水模，采用标准算法和软组织算法重建，3名阅片者独立评判图像质量。应用Pearson线性相关分析、配对t检验、方差分析和Kappa检验进行统计学分析。结果132例患者气管内、体外空气密度差范围在20．00～55．00HU，与体质量[（64．99±11．86）kg]、体质量／身高[（38．71±6．13）kg／m]及体质量指数（BMI）[（23．11±3．38）kg／m^2]呈正相关（r值分别为0．288、0．374、0．449，P值均〈0．01）。两种模型标准算法[噪声分别为（22．43±11．25）、（21．99±11．67）HU]与软组织算法[（16．55±9．08）、（16．42±9．40）HU]之间噪声差异有统计学意义（F=4．316，P〈0．05），软组织算法噪声水平低于标准算法，而与使用何种体模无关。软组织算法100mA时图像噪声水平与标准算法280mA时相当，PE模型图像信噪比（SNR）和对比噪声比（CNR）分别为23．05、20．52，不影响对栓塞的识别；软组织算法60mA时噪声水平与标准算法160mA时相当，PE模型图像SNR、CNR分别为18．01、15．97，亦不影响栓子定性观察；30mA以下图像质量明显下降，PE模型图像SNR、CNR分别在12．36、10．95以下，模拟栓子检出能力下降。3名阅片者图像质量判读结果之间一致性高（Kappa值分别0．807、0．712和0．904，P值均〈0．01）。结论100mA可能是比较理想的低剂量CTPA扫描条件；30mA可能是诊断所需的最低扫描条件；软组织算法成像能减少SNR损失。
Objective To investigate the feasibility of reduced radiation dose for CT pulmonary angiography （CTPA） and the possible lowest radiation threshold by a phantom study. Methods The CT value difference between air within the trachea and the extracorporeal background region was measured in 132 consecutive patients. A noise-measurement phantom and a pulmonary embolism （PE） phantom were made of phenol-formaldehyde, and both phantoms and a water phantom were scanned with standard and lower radiation doses as follow： 280, 200, 160, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, and 10 mA respectively, at a fixed voltage of 120 kVp. Standard and soft tissue algorithms were used to reconstruct the images. Three experienced doctors independently evaluate the image quality and the efficiency of detecting PE of the images with various doses. The Pearson correlation analysis, two-tailed paired t test, ANOVA, and Kappa test were employed for the statistical analysis. Results The CT value difference between air within the trachea and the extraeorporeal background region in 132 consecutive patients ranged from 20. 00 to 55.00 HU, which had a positive correlation with weight [ （ 64. 99 ± 11.86 ） kg ], weight-height ratio [ （ 38.71 ±6. 13 ） kg/m ], and BMI [ （ 23.11± 3.38 ） kg/m^2 ] （ r = 0. 228,0. 374,0. 449 respectively ; P 〈 0. 01）. The image noise level with soft-tissue reconstruction algorithm [ （16. 55 ± 9.08 ）, （16.42 ± 9.40） HU] was significantly lower than that of the image with standard reconstruction algorithm[ （22. 43 ± 11.25）,（21.99 ±11.67） HU] （F = 4.316, P 〈 0.05）.The image noise level with soft-tissue reconstruction algorithm at 100 mA was similar to that of the images with standard reconstruction algorithm at 280 mA, and the signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） of the image of PE phantom was 23.05 and 20. 52 respectively, without any impairment in detectability of embolus. The image noise level with soft-tissue reconstruction algorithm at 60 mA was similar to that of the image with standard reconstruction algorithm at 160 mA, while the SNR and CNR was 18.01 and 15.97 respectively, also with acceptable detectability of embolus. When the tube current was reduced below 30 mA, the image quality decreased significantly, with the SNR and CNR was lower than 12. 36 and 10. 95 respectively, and the detectability of embolus was degraded. The consistency of the image quality grading by 3 observers was exeellent（K =0. 807,0. 712,0. 904,respectively; P 〈0. 01 ）. Conclusions The 100 mA may potentially be the ideal low dose tube current setting, with radiation dose only equal to 36% of 280 mA （standard dose）. The 30 mA may possibly be a minimum radiation dose for detecting PE. The soft-tissue reconstruction algorithm was favorable in preserving the SNR when the radiation dose was reduced.
出处
《中华放射学杂志》
CAS
CSCD
北大核心
2009年第7期753-758,共6页
Chinese Journal of Radiology
关键词
肺栓塞
辐射剂量
模型
理论
体层摄影术
X线计算机
Pulmonary embolism
Radiation dosage
Models, theoretical
Tomography, X-ray computed
