摘要
目的探讨腹部CT单源瞬时kVp切换模式与常规CT120kVp扫描的射线剂量和图像噪声的关系。方法采用质量评价标准体模，对其中的水模部分分别进行能谱成像和常规螺旋扫描，获得常规扫描模式与能谱扫描模式mAs的回归方程，并计算出不同能谱成像（GSI）扫描参数所对应的常规120kVp扫描mAs。回顾性分析22例全腹部CT增强扫描患者资料。根据平扫常规扫描所使用的mAs选择相应的能谱模式进行增强门静脉期扫描，分别测量常规和能谱CT扫描在肝实质、膀胱区的图像噪声。采用配对t检验比较常规扫描与能谱扫描的射线剂量和图像噪声。结果22例患者CT能谱成像和常规螺旋扫描的CT剂量指数分别为（13．8±4．8）和（14．0±7．0）mGy，剂量长度乘积分别为（691．1±274．2）和（678．8±385．0）mGy·cm，差异均无统计学意义（t值分别为0．177和-0．260，P值均〉0．05）。在肝脏，65keV单能量图像的噪声为（7．6±1．4）HU，低于常规扫描滤波反投影（FBP）图像和20％自适应统计迭代重建（ASIR）图像[分别为（10．4±1．0）和（9．1±0．9）HU]，与40％ASIR图像相当[（7．8±0．7）HU]，高于60％ASIR图像噪声[（6．7±0．7）HU]；在膀胱，65keV单能量图像的噪声[（9．1±1．3）HU]低于常规扫描FBP图像[（10．5±1．3）HU]，与20％ASIR图像相当[（9．2±1．2）HU]，高于40％和60％ASIR图像的噪声[分别为（8．0±1．1）和（6．8±0．9）HU]。结论通过选择合适的参数，腹部CT能谱扫描与常规扫描的射线剂量相当；65keV单能量图像的噪声低于常规扫描的FBP重建图像、与20％～40％ASIR图像噪声相当，可在临床中常规应用。
Objective To investigate the radiation dose and image noise of abdominal CT with spectral imaging and conventional scan mode. Methods This was a retrospective study. The first part of this study was a phantom study. A standard quality assessment phantom was scanned with gemstone spectral imaging mode and conventional helical mode using 120 kVp with different mAs. A regression function for the mAs between conventional scan mode and spectral imaging mode was obtained. According to the regression function, the mAs on 120 kVp corresponding to different gemstone spectral imaging protocol were calculated. The second part of this study was a clinical study. Twenty-two patients who underwent contrast enhanced abdominal CT scanning were included. The pre-eontrast CT was seanned by a conventional mode with automatic exposure eontrol technique. According to the mAs of pre-eontrast scan,corresponding spectral imaging parameters were selected for the portal venous phase of post-contrast scan. Five sets of images with 5 mm slice thickness were reconstructed,with 65 keV monochromatic image for speetral imaging and FBP, 20% ,40% and 60% ASIR image for conventional imaging respectively. Image noise was measm＇ed on hepatic parenehyma and urinary bladder for each set of image. Radiation dose and image noise were compared between CT spectral imaging and conventional imaging with paired t-test. Results No significant differences were found for the CTDIvol [ （ 13.8 ± 4. 8 ） mGy versus （ 14. 0 ± 7. O） mGy ] and DLP · （ 691.1 ± 274. 2 ） mGy · em versus （678.8 ± 385.0） mGy · em ] between CT spectral imaging and conventional imaging. Monochromatic image （ 65 keV） by spectral imaging [ （7.6± 1.4） HU for hepatic parenehyma and （9. 1± 1.3） HU for urinary bladdery had equal image noise with 40%ASIR [ hepatic parenehyma： （7.8 ± 0. 7） HU] and 20% ASIR [urinary bladder： （9. 2 ± 1.2） HU] and lower image noise than FBP image E （10. 4± 1.0） HU for hepatic parenehyma and （10. 5 ± 1.3） HU
出处
《中华放射学杂志》
CAS
CSCD
北大核心
2013年第2期116-120,共5页
Chinese Journal of Radiology
基金
上海市科学技术委员会医学重点项目基金资助项目（10411953000）
