CAJ | 학술논문

目的分析胸部低剂量CT扫描图像噪声与伪影的影响因素及分布特点.方法应用组织等效胸部模型置于Philips Brilliance 64层CT机以常规剂量(管电压120 kV,管电流250 mAs)和低剂量(管电压120 kV,管电流50、30和21 mAs)分别扫描,测量、记录模型各部位CT值、CT值噪声标准差(SO),分别行方差分析.对200例肺结节患者以30或21 mAs剂量组行小范围低剂量扫描,通过卡方检验分析不同剂量扫描影像噪声和伪影严重程度与患者性别、体型的关系及在肺部的分布特点.结果不同扫描剂量条件下测量模型各部位CT值差异均无统计学意义:肺-777.3～-758.2 HU(F=0.992,P>0.05),胸壁107.9～111.3 HU(F=2.044,P>0.05),椎骨835.6～875.3 HU(F=1.453,P>0.05);而CT值SD差异有统计学意义:肺9.5～29.0 HU(F=108.7,P<0.01),胸壁10.1～32.4 (F=84.3,P<0.01),椎骨19.2～57.1 HU(F=30.6,P<0.01),且随电流降低而增加.临床患者低剂量扫描显示,不同性别组图像噪声和伪影严重程度(男性无或轻微者74例,严重者17例;女性无或轻微者81例,严重者28例)差异无统计学意义(X~2=2.294,P>0.05),不同体型组的体质量指数[(BMI)<18.5组无或轻微者29例,严重者2例;18.5≤BMI<24.0组无或轻微者120例,严重者13例;BMI≥24.0组无或轻微者6例,严重者30例]差异有统计学意义(X~2=128.274,P<0.01).低剂量扫描图像的噪声和伪影在上肺野(无或轻微者80例,严重者38例;X~2=18.918,P<0.01)、肺野后部(无或轻微者89例,严重者33例;X~2=6.760,P<0.05)较严重.结论低剂量CT扫描图像噪声增加,噪声和伪影在肺野后、上部较严重,可能和骨骼分布有关.应根据受检者BMI调整扫描方案(mAs值),做到扫描方案个体化.
목적 분석흉부저제량CT소묘도상조성여위영적영향인소급분포특점.방법 응용조직등효흉부모형치우Philips Brilliance 64층CT궤이상규제량(관전압120 kV,관전류250 mAs)화저제량(관전압120 kV,관전류50、30화21 mAs)분별소묘,측량、기록모형각부위CT치、CT치조성표준차(SO),분별행방차분석.대200례폐결절환자이30혹21 mAs제량조행소범위저제량소묘,통과잡방검험분석불동제량소묘영상조성화위영엄중정도여환자성별、체형적관계급재폐부적분포특점.결과 불동소묘제량조건하측량모형각부위CT치차이균무통계학의의:폐-777.3～-758.2 HU(F=0.992,P>0.05),흉벽107.9～111.3 HU(F=2.044,P>0.05),추골835.6～875.3 HU(F=1.453,P>0.05);이CT치SD차이유통계학의의:폐9.5～29.0 HU(F=108.7,P<0.01),흉벽10.1～32.4 (F=84.3,P<0.01),추골19.2～57.1 HU(F=30.6,P<0.01),차수전류강저이증가.림상환자저제량소묘현시,불동성별조도상조성화위영엄중정도(남성무혹경미자74례,엄중자17례;녀성무혹경미자81례,엄중자28례)차이무통계학의의(X~2=2.294,P>0.05),불동체형조적체질량지수[(BMI)<18.5조무혹경미자29례,엄중자2례;18.5≤BMI<24.0조무혹경미자120례,엄중자13례;BMI≥24.0조무혹경미자6례,엄중자30례]차이유통계학의의(X~2=128.274,P<0.01).저제량소묘도상적조성화위영재상폐야(무혹경미자80례,엄중자38례;X~2=18.918,P<0.01)、폐야후부(무혹경미자89례,엄중자33례;X~2=6.760,P<0.05)교엄중.결론 저제량CT소묘도상조성증가,조성화위영재폐야후、상부교엄중,가능화골격분포유관.응근거수검자BMI조정소묘방안(mAs치),주도소묘방안개체화.
Objective To analyze the image noise and artifact of low-dose chest CT scanning and the distribution pattern. Methods A chest phantom equivalent to human tissue was scanned by 64 slices spiral scanner at standard dose (250 mAs) and low-dose (50, 30,and 21 mAs) respectively, HU in sites of the phantom and SD of which was recorded. 200 patients with pulmonary nodules were scanned at 30 or 21 mAs for minimal length. The relationship between severity of noise and artifact in chest low-dose CT scanning and gender or body mass index (BMI) of the patients, as well as the distribution of noise and artifact was evaluated. Results There was no statistical difference between the HU in sites of the phantom: lung (-777.3-- -758.2 HU, F=0.992, P<0.01), chest wall (107.9--111.3 HU, F=2.044, P>0.05), vertebra (835.6--875.3 HU, F=1.453, P>0.05), while the SD of which was of statistical signification: lung (9.5--29.0 HU, F=108.7, P<0.01), chest wall (10.1--32.4 HU, F=84.3, P<0.01), vertebra (19.2--57.1 HU, F=30.6, P<0.01),tbe SD increased with the decrease of the tube current. There was no statistical difference between male (in which 74 cases no or mild, 17 cases severe)and female (81 cases no or mild, and 28 cases severe)in image noise and artifact in low-dose images (X~2=2.294, P>0.05), and significant difference between groups of different BMI(in BMI<18.5 group, 29 cases no or mild,2 cases severe, in group of 18.5≤BMI<24.0, 120 cases no or mild, 13 cases severe, and in group of BMI≥24.0, 6 cases no or mild, 30 cases severe, X~2=128.274, P<0.01). The noise andartifact was greater in the upper (80 cases no or mild, 38 cases severe, X~2=18.918, P<0.01) and dorsal field (89 cases no or mild, 33 cases severe, X~2=6.760, P<0.05). Conclusions The image noise and artifact was significant in low-dose CT, especially in the dorsal and upper field of the lung, which might be attributed to the distribution of skeleton in the chest. It was recommended that scanning protocol (mAs value) be individualized adjusted in according to the patients BMI.