CAJ | 학술논문

目的探讨腹部CT单源瞬时kVp切换模式与常规CT 120 kVp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120 kVp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,65 keV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,65 keV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；65 keV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.
목적 탐토복부CT단원순시kVp절환모식여상규CT 120 kVp소묘적사선제량화도상조성적관계.방법 채용질량평개표준체모,대기중적수모부분분별진행능보성상화상규라선소묘,획득상규소묘모식여능보소묘모식mAs적회귀방정,병계산출불동능보성상(GSI)소묘삼수소대응적상규120 kVp소묘mAs.회고성분석22례전복부CT증강소묘환자자료.근거평소상규소묘소사용적mAs선택상응적능보모식진행증강문정맥기소묘,분별측량상규화능보CT소묘재간실질、방광구적도상조성.채용배대t검험비교상규소묘여능보소묘적사선제량화도상조성.결과 22례환자CT능보성상화상규라선소묘적CT제량지수분별위(13.8±4.8)화(14.0±7.0) mGy,제량장도승적분별위(691.1±274.2)화(678.8 ±385.0)mGy·cm,차이균무통계학의의(t치분별위0.177화-0.260,P치균＞0.05).재간장,65 keV단능량도상적조성위(7.6±1.4)HU,저우상규소묘려파반투영(FBP)도상화20％자괄응통계질대중건(ASIR)도상[분별위(10.4±1.0)화(9.1±0.9)HU],여40％ ASIR도상상당[(7.8±0.7)HU],고우60％ ASIR도상조성[(6.7±0.7)HU]；재방광,65 keV단능량도상적조성[(9.1±1.3)HU]저우상규소묘FBP도상[(10.5±1.3)HU],여20％ ASIR도상상당[(9.2±1.2)HU],고우40％화60％ ASIR도상적조성[분별위(8.0±1.1)화(6.8±0.9) HU].결론 통과선택합괄적삼수,복부CT능보소묘여상규소묘적사선제량상당；65 keV단능량도상적조성저우상규소묘적FBP중건도상、여20％～40％ ASIR도상조성상당,가재림상중상규응용.
Objective To investigatc 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-contrast CT was scanned by a conventional mode with automatic exposure control technique.According to the mAs of pre-contrast 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 spectral imaging and FBP,20％,40％ and 60％ ASIR image for conventional imaging respectively.Image noise was measured on hepatic parenchyma 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 ± 7.0) m Gy] and DLP [(691.1 ± 274.2)mGy· cm versus (678.8 ± 385.0) mGy · cm] between CT spectral imaging and conventional imaging.Monochromatic image (65 keV) by spectral imaging [(7.6 ± 1.4) HU for hepatic parenchyma and (9.1 ± 1.3) HU for urinary bladder] had equal image noise with 40％ ASIR [hepatic parenchyma: (7.8 ±0.7) HU] and 20％ ASIR [urinary bladder: (9.2 ± 1.2) HU] and lower image noise than FBP image [(10.4 ± 1.0) HU for hepatic parenchyma and (10.5 ± 1.3) HU for urinary bladder] by conventional imaging.Conclusions The radiation dose of CT spectral imaging and conventional CT scan is equivalent with spectral imaging parameters appropriately selected.Monochromatic image (65 keV) by CT spectral imaging has lower image noise than FBP image,and same image noise with 40％ ASIR (hepatic parenchyma)and 20％ ASIR (urinary bladder) by conventional imaging.