多层螺旋CT自动毫安技术对腰椎患者扫描剂量减少的可行性研究

Objective To investigate the feasibility of achieving consistent image quality with dose reduction technology in lumber spine MSCT examination with Z-axis automatic tube current modulation (ATCM). Methods Forty-eight patients diagnosed as lumber intervertebral disc protrution scanned twice by MSCT before and after interventional operations with the same coverage from third lumbar vertebra to first sacral vertebra. The first scan (FM) was with fixed tube current of 320 mAs. The follow-up scan was with ATCM with noise index (NI) of 12.0 HU. At the levels of L3-4, L4-5 and 15-S1, image quality, image noise and radiation dose were measured and analyzed. Image quality and radiation dose were compared by paired t-test and the image noise was compared by ANOVA test. Results The dosage of the ATCM had a 31.3% reduction compared with FM, the average DLP was(187.9±66.4)mGy·cm and(273.4±45.4) mGy·cm respectively, where t = 8.205, P < 0.05. The average noise and their deviations for the FM group were (9.8±2.4) HU,(9.9±2.4) HU, and (11.5±3.2) HU at level of L3-4, L4-5, 15-S1, respectively. With ATCM, the average noise was(12.0±0.8) HU, (11.7±0.6) HU, and (11.7±1.4) HU, respectively. There was statistical difference between the two groups (F = 23.31, P < 0.05). The image quality scores for the FM group were (4.7±0.3), (4.5±0.2), (4.5±0.2) and showed no statistical difference to ATCM group (4.6±0.3), (4.5±0.2), (4.5±0.2) at level of L3-4, L4-5, L5-S1, respectively, where t = 1.000, P > 0.050 Conclusion ATCM technique with the noise index setting at 12.0 HU can achieved a 31.3% dose reduction while keep the consistent image quality for lumbar spine MSCT study.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

应用心电脉冲技术降低64层螺旋CT冠状动脉成像的辐射剂量

Objective To evaluate the value of reducing radiation dose with ECG-pulsing and image quality in 64-row multi-alice CT coronary angiography.Methods Fifty-nine consecutive patients whose heart rates were less than 80 beat per minute and cardiac rhythm was regular were randomly divided into two groups from October 26, 2007 to March 12, 2008.Conventional technique of CT coronary angiography was employed in group 1, while ECG-pulsing technique was applied in group 2.CT dose index volume (CTDIvol) and dose length product (DLP) were obtained automatically, and then the corresponding effective dose (ED) were calculated.The quality scores were performed on obtained imaging by using double blind method.Student t-test was applied in the comparison of value of CTDIvol, value of ED and quality of imagiugbetween two groups.Results The value of CTDIvol was (70.0±1.1) and (39.0±2.7) mGy, the value of ED was (16.8±2.0) and (9.5±1.7) rosy in group 1 and group 2, respectively, which reached statistically significant differences between the groups(t=57.675,15.346 ,P <0.01, respectively). The quality scores of coronary images were 3.8±0.2 and 3.8±0.1 in the groups, which did not reach the statistical significance (t=-0.222, P 0.05).Conclusions The proper application of ECG-Pulsing technology in 64-slice spiral CT coronary angiography can reduce radiation dose significantly while having no influence on the quality of the imaging.     

低剂量CT肺动脉成像的实验研究

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 in132 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 independendy 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 extracorpereal 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/m2](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-w-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 excellent(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-tiasue reconstruction algorithm was favorable in preserving the SNR when the radiation dose was reduced.     

ASiR算法结合自动管电流调制技术在胸部低剂量CT中的应用研究

目的:研究自适应性统计迭代重建(ASiR)算法结合自动管电流调制技术在MSCT( GE Discovery CTHD 750HD)胸部扫描中的应用,探讨胸部低剂量扫描的可行性.方法:将100名拟行宝石CT胸部平扫的患者随机分为A、B两组,每组50名.使用自动管电流调制技术扫描,A组预设噪声指数(NI)为15HU,B组预设NI为25HU,并采用不同权重的ASiR进行图像重建.记录两组患者CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP)并计算有效剂量(ED).三位放射科医师采用盲法对图像质量进行评估(5分制).结果:A组CTDIvo1为4.22 mGy,ED为2.51mSv,B组CTDIvol为1.51mGy,ED为0.89mSv,分别比A组降低了64.22％和64.54％.A、B两组的图像质量均能满足临床诊断要求.结论:使用ASiR重建算法结合自动管电流调制技术进行宝石CT胸部扫描,可以大幅降低辐射剂量,同时保证图像质量.     

多层螺旋CT低剂量扫描技术在甲状腺增强扫描中的临床应用

目的：探讨多层螺旋 CT 低剂量扫描技术在甲状腺增强扫描中的临床应用价值。方法80例患者随机分为4组(每组各20例),4组分别为：A 组,120 kV、180 mA;B 组,120 kV、100 mA;C 组,100 kV、180 mA;D 组,100 kV、100 mA。主观评价图像质量并评分,统计甲状腺 CT 值、图像背景噪声(N)、图像信噪比(SNR)、CT 剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效辐射剂量(ED)并进行对比分析。结果4组图像主观评分为3.90±0.31、3.75±0.44、3.70±0.47、3.60±0.60,SNR 为26.34±3.13、25.08±1.87、25.86±2.38、24.87±2.20,四者无统计学差异(P >0.05);甲状腺 CT 值为(168.55±13.39)HU、(170.70±11.34)HU、(185.20±22.35)HU、(190.55±21.38)HU,N 为(6.48±0.84)HU、(6.83±0.45)HU、(7.19±0.86)HU、(7.66±1.01)HU, CTDIvol 为(10.95±0.00)mGy、(6.08±0.00)mGy、(6.59±0.00)mGy、(3.66±0.00)mGy,DLP 为(145.67±8.79)mGy·cm、(84.58±4.94)mGy·cm、(89.86±3.26)mGy·cm、(50.20±1.89)mGy·cm,ED 为(0.73±0.04)mSv、(0.42±0.03)mSv、(0.45±0.03)mSv、(0.25±0.01)mSv,四者有统计学差异(P <0.05)。结论多层螺旋 CT 低剂量扫描技术既能保证图像质量又能有效降低甲状腺增强 CT 检查的辐射剂量。     

自动管电流调制技术在PET/CT中的实际应用

目的 探讨自动管电流调制（ATCM）技术对PET/CT受检者CT图像质量及有效剂量的影响。 方法 将2017年10月至2018年7月接受PET/CT检查的90例受检者按系统抽样方法分为A、B、C 3组,每组各30例。CT采用ATCM扫描。A、B两组采用的管电流区间为60~240 mA,噪声指数分别为10、15;C组管电流区间为60~180 mA,噪声指数为15。记录容积CT剂量指数（CTDI_vol）和剂量长度乘积（DLP）,根据公式估算有效剂量。由两位核医学科主治及以上医师采用双盲法对受检者颈部、胸部、腹部、盆腔CT图像质量进行评分,测定图像CT值、噪声值并计算信噪比。采用方差分析比较3组的噪声值、信噪比差异,采用非参数检验中的Kruskal-Wallis检验比较3组的CTDI_vol、DLP、有效剂量差异,组内两两比较采用Nemenyi检验。 结果 A、B、C 3组受检者所有图像质量评分均不低于3分,且差异均有统计学意义(F=3.77~14.42,均P<0.05)。A、B、C 3组受检者的噪声值[（11.90±2.83）~（26.03±3.74）]、信噪比[（2.03±0.34）~（4.35±0.71）]差异均有统计学意义（F=38.01~64.20和F=32.09~81.62,均P<0.05）,CT图像质量均能满足临床诊断要求。A、B、C 3组受检者的CTDI_vol[（12.44±0.53）、（9.39±2.01）和（7.05±1.03）mGy]、DLP[（998.45±96.04）、（741.60±168.87）和（571.29±97.41） mGy·cm]、有效剂量[（14.98±1.44）、（11.12±2.53）和（8.57±1.46） mSv]的差异均有统计学意义（χ2=62.18、57.19和57.16,均P<0.05）。其中,C组比A组的有效剂量低,差异有统计学意义（χ2=56.55,P<0.05）。 结论 应用PET/CT ATCM技术,合理调节管电流区间及噪声指数,保证图像质量的同时可有效降低受检者的有效剂量。      

Effective dose determination using an anthropomorphic phantom and metal oxide semiconductor field effect transistor technology for clinical adult body multidetector array computed tomography protocols

PURPOSE: To determine the organ doses and total body effective dose (ED) delivered to an anthropomorphic phantom by multidetector array computed tomography (MDCT) when using standard clinical adult body imaging protocols. MATERIALS AND METHODS: Metal oxide semiconductor field effect transistor (MOSFET) technology was applied during the scanning of a female anthropomorphic phantom to determine 20 organ doses delivered during clinical body computed tomography (CT) imaging protocols. A 16-row MDCT scanner (LightSpeed, General Electric Healthcare, Milwaukee, Wis) was used. Effective dose was calculated as the sum of organ doses multiplied by a weighting factor determinant found in the International Commission on Radiological Protection Publication 60. Volume CT dose index and dose length product (DLP) values were recorded at the same time for the same scan. RESULTS: Effective dose (mSv) for body MDCT imaging protocols were as follows: standard chest CT, 6.80 +/- 0.6; pulmonary embolus CT, 13.7 +/- 0.4; gated coronary CT angiography, 20.6 +/- 0.4; standard abdomen and pelvic CT, 13.3 + 1.0; renal stone CT, 4.51 + 0.45. Effective dose calculated by direct organ measurements in the phantom was 14% to 37% greater than those determined by the DLP method. CONCLUSIONS: Effective dose calculated by the DLP method underestimates ED as compared with direct organ measurements for the same CT examination. Organ doses and total body ED are higher than previously reported for MDCT clinical body imaging protocols.     

Relationships between physical dose quantities and patient dose in CT

Patient dose in CT is usually expressed in terms of organ dose and effective dose. The latter is used as a measure of the stochastic risk. Determination of these doses by measurements or calculations can be time-consuming. We investigated the efficacy of physical dose quantities to describe the organ dose and effective dose. For various CT examinations of the head, neck and trunk, organ doses and effective doses were determined using conversion factors. Dose free-in-air on the axis of rotation (Dair) and weighted computed tomography dose index (CTDIw) were compared with the absorbed doses of organs which are located totally within the body region examined. Dose-length product (DLP) was compared with the effective dose. The ratio of the organ dose to CTDIw was 1.37 (0.87-1.79) mSv mGy-1. DLP showed a significant correlation with the effective dose (p < 0.005). The average ratio of effective dose to DLP was 0.28 x 10(-2) mSv (mGy cm)-1 for CT of the head, 0.62 x 10(-2) mSv (mGy cm)-1 for CT of the neck and 1.90 x 10(-2) mSv (mGy cm)-1 for CT of the trunk. CTDIw and DLP can be used for estimating the organ dose and effective dose associated with CT examinations of the head, neck and trunk.     

64层螺旋CT自动毫安技术对降低下肢动脉 血管成像辐射剂量的研究

目的 探讨64层螺旋CT自动毫安技术(ATCM)对降低下肢动脉血管成像辐射剂量的可行性。方法 通过预实验改变噪声指数(NI)调节管电流,得出NI值为10 HU时图像质量与辐射剂量匹配较佳。搜集52例疑有下肢动脉闭塞糖尿病及高血压病患者病例,随机分为实验组和对照组行自肾下腹主动脉至足底的CT容积扫描,每组病例26例。对照组采用常规固定300 mA(FM组),实验组采用NI为10 HU的自动毫安(ATCM组)技术。分别选择肾下腹主动脉、髋关节水平股动脉、 NFDB1 动脉及踝关节胫前动脉平面作为观察平面,对两种毫安技术的图像质量、图像噪声和辐射剂量均采用 t 检验方法进行统计学分析。结果 FM组的辐射剂量CTDI_vol为10.81 mGy,平均DLP为(1280.4±124.7)mGy·cm,ATCM组的平均CTDI_vol为(5.14±1.23)mGy,平均DLP为(582.86±150.41)mGy·cm,比FM组降低约54.4%,两组差异有统计学意义(CTDI_vol、DLP的 t 值分别为13.13、17.36, P 值均<0.05)。FM组的4个选取平面图像噪声分别为13.8±4.04、14.53±2.79、5.69±1.38、(4.75±1.38) HU。ATCM组分别为10.76±2.11、12.13±2.96、10.47±2.96、(6.17±1.53) HU,两组差异有统计学意义( t 值分别为2.911、3.038、7.287及3.186, P 值均<0.05),ATCM组肾下腹主动脉、髋关节水平股动脉层面的图像噪声较FM组的低,而 NFDB1 动脉、踝关节胫前动脉层面的图像噪声较FM组的高,ATCM组图像噪声变异度小,图像更加均匀。FM组图像质量评分平均为2.654±0.562,ATCM组图像评分平均为2.462±0.582,两组图像质量评分差异无统计学意义( t =1.21, P ＞0.05)。结论 使用噪声指数为10的下肢动脉ATCM技术,在保证图像质量的情况下可以降低辐射剂量约54.4%。     

多层螺旋CT自动毫安技术对腰椎患者扫描剂量减少的可行性研究

目的 探讨MSCT Z轴自动毫安(ATCM)调制扫描技术对患者腰椎CT扫描剂量减少的可行性.方法 对48例腰椎间盘突出症患者分椎间盘介入术前检查及术后复查2组,进行L3～S1相同覆盖范围MSCT检查.术前检查组采用常规固定320 mAs(FM组),术后复查组采用噪声指数为12.0 HU的Z轴ATCM技术(ATCM组).分别选择L3～4、L4～5、L5～S1椎间盘平面作为观察平面,对2种毫安技术的图像质量、图像噪声和辐射剂量进行统计学分析.图像质量评分、辐射剂量比较采用配对t检验,图像噪声比较采用单因素方差分析.结果 FM组的剂量长度乘积(DLP)平均为(273.4±45.4)mGy·cm,ATCM组为(187.9±66.4)mGy·cm,ATCM组比FM组降低31.3%(t=8.205,P<0.05);FM组的3个椎间盘平面图像噪声变异分别为(9.8±2.4)、(9.9±2.4)、(11.5±3.2)HU,ATCM组分别为(12.0±0.8)、(11.7±0.6)、(11.7±1.4)HU,ATCM组的图像噪声变异小于FM组(F=23.31,P<0.05);FM组3个椎间盘平面的图像质量评分分别为(4.7±0.3)、(4.5±0.2)、(4.5±0.2)分,ATCM组分别为(4.6±0.3)、(4.5±0.2)、(4.5±0.2)分,两组图像质量评分差异无统计学意义(t=1.000,P>0.05).结论 使用噪声指数为12.0 HU的ATCM技术,在保证图像质量的情况下可以降低辐射剂量约31.3%.     

Radiation dose evaluation in 64-slice CT examinations with adult and paediatric anthropomorphic phantoms

The objective of this study was to evaluate the organ dose and effective dose to patients undergoing routine adult and paediatric CT examinations with 64-slice CT scanners and to compare the doses with those from 4-, 8- and 16-multislice CT scanners. Patient doses were measured with small (<7 mm wide) silicon photodiode dosemeters (34 in total), which were implanted at various tissue and organ positions within adult and 6-year-old child anthropomorphic phantoms. Output signals from photodiode dosemeters were read on a personal computer, from which organ and effective doses were computed. For the adult phantom, organ doses (for organs within the scan range) and effective doses were 8–35 mGy and 7–18 mSv, respectively, for chest CT, and 12–33 mGy and 10–21 mSv, respectively, for abdominopelvic CT. For the paediatric phantom, organ and effective doses were 4–17 mGy and 3–7 mSv, respectively, for chest CT, and 5–14 mGy and 3–9 mSv, respectively, for abdominopelvic CT. Doses to organs at the boundaries of the scan length were higher for 64-slice CT scanners using large beam widths and/or a large pitch because of the larger extent of over-ranging. The CT dose index (CTDI_vol), dose–length product (DLP) and the effective dose values using 64-slice CT for the adult and paediatric phantoms were the same as those obtained using 4-, 8- and 16-slice CT. Conversion factors of DLP to the effective dose by International Commission on Radiological Protection 103 were 0.024 mSv⋅mGy⁻¹⋅cm⁻¹ and 0.019 mSv⋅mGy⁻¹⋅cm⁻¹ for adult chest and abdominopelvic CT scans, respectively.X-ray CT scanners have made remarkable advances over the past few years, contributing to the improvement of diagnostic image quality and the reduction of examination time. CT scanners with 64 slices, the clinical use of which started quite recently in many medical facilities, has enabled a large number of thin slices to be acquired in a single rotation. 64-slice CT technology accelerated the practical use of three-dimensional body imaging techniques such as coronary CT angiography and CT colonography with an increasing number of CT examinations. The increase in CT examination frequency not only for adults but also for children and the higher doses in CT examinations compared with other X-ray diagnostic procedures have raised concerns about patient doses and safety. An understanding of patient doses requires the evaluation of organ and effective doses for patients undergoing CT examinations, although these dose values in 64-slice CT scans have seldom been reported.One common method for estimating organ and effective doses is dose calculation from the CT dose index (CTDI) or dose–length product (DLP), which are both used as readily available indicators of radiation dose in CT examinations. Organ and effective doses can be estimated from the CTDI or DLP, and conversion factors derived from Monte Carlo simulation of photon interactions within a simplified mathematical model of the human body [1]. Another method is based on measurement using thermoluminescence dosemeters (TLDs) implanted in various organ positions within an anthropomorphic phantom [2–6]. Although TLD dosimetry is considered to be the standard method for measuring absorbed doses in a phantom, the dose measurement is laborious and time consuming. Hence, we devised an in-phantom dosimetry system using silicon photodiode dosemeters implanted in various organ positions, where absorbed dose at each position could be read electronically. In the present study, we evaluated organ and effective doses with 64-slice CT scan protocols used clinically for adult and paediatric patients undergoing chest and abdominopelvic CT examinations. We compared the doses with published dose values for 4-, 8- and 16-slice CT, and indicated the conversion factor of DLP to the effective dose in each examination of the chest and abdomen–pelvis for 64-slice CT scanners.     

自动管电流模式下管电压对CT辐射剂量和影像质量影响的模体研究

目的 探讨自动管电流调制模式下行头颈部和胸部CT扫描时,管电压的改变对辐射剂量及影像质量的影响。方法 自动管电流和自动管电压模式下,对头颈部和胸部模体进行常规CT扫描。自动管电流模式下,管电压分别手动选择70、80、100、120和140 kV,对头颈部和胸部模体进行常规CT扫描。每种管电压下定位像扫描3次,再进行1次螺旋扫描。头颈部模体在眼眶中心及第5颈椎（C5）椎体上缘层面选取感兴趣区（ROI）,胸部模体在肺尖及气管分叉层面选取ROI,测量记录对比噪声比（CNR）。用热释光剂量计（TLD）测量每次扫描时眼晶状体和乳腺的器官剂量（取3次测量的平均值）,计算定位像和螺旋扫描的累积值。记录每次扫描的容积CT剂量指数（CTDI_vol）,并计算CTDI_vol累积值。最后通过计算品质因数（FOM）,找到最优化的管电压值。结果 自动管电流和自动管电压模式时,头颈部自动选择120 kV和108 mAs,胸部自动选择80 kV和167 mAs。自动管电流模式时,手动选择70 kV时眼晶状体辐射剂量和CTDI_vol值最小（分别为0.779和4.070 mGy）,140 kV时眼晶状体辐射剂量和CTDI_vol值最大（分别为2.571和25.670 mGy）。70 kV时乳腺辐射剂量和CTDI_vol值最小（分别为0.698和0.900 mGy）,140 kV时乳腺辐射剂量和CTDI_vol值最大（分别为3.452和7.400 mGy）。CNR值在眼眶和C5椎体上缘层面分别为51.30~118.36和80.78~173.12,在肺尖和气管分叉层面分别为50.15~129.58和49.63~115.40。FOM因子在眼眶层面80 kV最大,在C5椎体上缘层面120 kV最大,在肺尖和气管分叉层面都是70 kV最大。头颈部模体最佳管电压：眼眶层面手动100 kV,颈部层面自动管电压模式（120 kV）。胸部模体最佳管电压：手动100 kV。结论 管电压的选择对CT扫描的辐射剂量和影像质量影响较大。对于常规CT扫描,手动100 kV适合眼眶区域扫描,自动120 kV适合颈部区域扫描,手动100 kV适合胸部扫描。     

Radiation doses to patients receiving computed tomography examinations in British Columbia.

OBJECTIVE: To estimate the diagnostic reference levels and effective radiation dose to patients from routine computed tomography (CT) examinations in the province of British Columbia, Canada. METHODS: The patient weight, height and computed tomography dose index or dose linear product (DLP) were recorded on study sheets for 1070 patients who were referred for clinically indicated routine CT examinations at 18 radiology departments in British Columbia. Sixteen of the scanners were multidetector row scanners. RESULTS: The average patient dose varied from hospital to hospital. The largest range was found for CT of the abdomen, for which the dose varied from 3.6 to 26.5 (average 10.1) mSv. For head CT, the range was 1.7 to 4.9 (average 2.8) mSv; for chest CT, it was 3.8 to 26 (average 9.3) mSv; for pelvis CT, it was 3.5 to 15.5 (average 9.0) mSv; and for abdomen-pelvis CT, it was 7.3 to 31.5 (average 16.3) mSv. Reference dose values were calculated for each exam. These DLP values are as follows: head, 1300 mGy cm; chest, 600 mGy cm; abdomen, 920 mGy cm; pelvis, 650 mGy cm; and abdomen-pelvis, 1100 mGy cm. CONCLUSION: Among hospitals, there was considerable variation in the DLP and patient radiation dose for a specific exam. Reference doses and patient doses were higher than those found in similar recent surveys carried out in the United Kingdom and the European Union. Patient doses were similar to those found in a recent survey in Germany.