Optimizing Imaging Quality and Radiation Dose by the Age-Dependent Setting of Tube Voltage in Pediatric Chest Digital Radiography

Objective

The quality and radiation dose of different tube voltage sets for chest digital radiography (DR) were compared in a series of pediatric age groups.

Materials and Methods

Forty-five hundred children aged 0-14 years (yr) were randomly divided into four groups according to the tube voltage protocols for chest DR: lower kilovoltage potential (kVp) (A), intermediate kVp (B), and higher kVp (C) groups, and the fixed high kVp group (controls). The results were analyzed among five different age groups (0-1 yr, 1-3 yr, 3-7 yr, 7-11 yr and 11-14 yr). The dose area product (DAP) and visual grading analysis score (VGAS) were determined and compared by using one-way analysis of variance.

Results

The mean DAP of protocol C was significantly lower as compared with protocols A, B and controls (p < 0.05). DAP was higher in protocol A than the controls (p <0.001), but it was not statistically significantly different between B and the controls (p = 0.976). Mean VGAS was lower in the controls than all three protocols (p < 0.001 for all). Mean VGAS did not differ between protocols A and B (p = 0.334), but was lower in protocol C than A (p = 0.008) and B (p = 0.049).

Conclusion

Protocol C (higher kVp) may help optimize the trade-off between radiation dose and image quality, and it may be acceptable for use in a pediatric age group from these results.     

多排螺旋CT低剂量扫描在小儿胸部的应用

目的评估低剂量扫描在小儿胸部的应用。方法水模测试:在水体模的同一层面做3mm层厚的150、80、50、35、15mAs扫描。在每幅图像的5个相同感兴趣区测CT值,做CT值的均匀性和噪声水平比较。病例扫描:随机选择肺部感染的患儿40例,先行常规剂量(150mAs)扫描以确定感染部位,再在感染局部做低剂量扫描(50,35mAs及15mAs)。其他参数为:120kV,床进28.8mm/圈,0.5s/圈,16×1.5mm准直,重建层厚及间隔均为3mm。比较不同剂量的CT权重剂量指数(CTDIw)及剂量长度乘积(DLP);由2位高年资医师按优、良、合格及不合格的等级盲法评价不同剂量的图像质量,结果进行统计学处理。结果CT图像的均匀性随着扫描剂量的减少而变差,图像噪声水平随扫描剂量的减少而增高。小儿胸部150、50、35、15mAs的CTDIw分别为:10.0、3.3、2.3、1.0mGy,其DLP分别为:117.8、39.3、27.5和11.8;150、50、35mAs的符合临床诊断图像(包括优,良,合格3个等级)所占比例,肺窗和纵隔窗均不小于90%,而15mAs的不合格图像所占比例为20%。结论在保证图像质量的前提下,多排螺旋CT小儿胸部检查采用35mAs的扫描条件较为适宜。     

多层螺旋CT扫描降低仟伏值对婴幼儿胸部图像质量的影响

目的:比较婴幼儿胸部低仟伏值CT扫描与常规扫描的图像质量,探讨降低仟伏值低剂量扫描应用于婴幼儿胸部检查的可行性。方法:体模测试:用120和90kV条件扫描体模的空间分辨力插件,选择相同位置的4帧图像测量平均空间分辨力;再用相同的方法扫描体模的水层,测量每组4帧图像的平均CT值标准差,作2组的噪声水平比较。病例扫描:选择胸部检查的患儿80例,随机分成2组,每组40例。2组分别用常规剂量(120kV,80mAs)和低剂量(90kV,80mAs)扫描,层厚5mm。比较不同剂量的CT权重剂量指数(CTDIvol)及剂量长度乘积(DLP);测量、比较2组图像降主动脉处的噪声值;并由2位医师按优、合格、不合格的等级盲法评价2组图像质量。结果:90kV扫描的CTDIvol为2.3mGy,DLP为26.4mGy·cm,与常规剂量的比值为43.4%和43.1%。低剂量图像的噪声水平(H=0.66%)较常规组(H=0.44%)高,两者差异有统计学意义(t=11.86,P<0.001)。虽然低剂量组的优质图像所占比率有所降低,但不存在不合格图像,所有低剂量图像都符合临床诊断要求。结论:90kV可以作为多层螺旋CT婴幼儿日常胸部检查的扫描条件。     

Extrapulmonary Tuberculosis: Imaging Features Beyond the Chest

The purpose of this pictorial review is to illustrate the various imaging findings of extrapulmonary tuberculosis. Manifestations of cardiac, central nervous system, head and neck, musculoskeletal, abdominal, genitourinary, and breast tuberculosis will be discussed. Extrapulmonary tuberculosis presents a difficult diagnostic challenge for the radiologist and requires a high index of suspicion, particularly in high-risk populations.