64层螺旋CT冠状动脉成像低剂量技术的应用价值

目的 探讨低剂量技术在64层螺旋CT冠状动脉成像中的应用. 资料与方法 连续选取100例患者进行冠状动脉检查.将患者分为常规组(C组)和低剂量组(L组),每组50例.C组采用标准采集方法 ,L组采用低剂量采集方法 ,然后对C组和L组图像质量、噪声、容积CT剂量指数(CTDIvol)和有效剂量(ED)进行评估. 结果 C组和L组图像质量评分分别为(3.56±0.54)分和(3.62±0.57)分,图像噪声分别为27.54±4.52和27.30±6.15,两组间无显著差异(P>0.05).但C组和L组的CTDIvol分别为(87.91±8.38) mGy/cm和(43.11±4.38) mGy/cm,ED分别为(17.96±1.71) mSv和(8.75±0.83) mSv,L组的CTDIvol和ED均明显低于C组(P< 0.05). 结论 低剂量采集方法 既可明显降低受检者的射线剂量又能满足诊断需求.     

CT低剂量联合迭代算法在输尿管结石诊断中的应用

目的 探讨CT低剂量联合迭代算法在输尿管结石诊断中的应用价值.方法 90例输尿管结石患者在首次检查均应用常规剂量扫描(120 kV,400 mAs),采用滤波反投影算法(FBP)薄层重组,保守治疗后结石未排出.复查CT应用低剂量扫描随机分为3组(A组:120 kV,200 mAs;B组:120 kV,150 mAs;C组:120 kV,100 mAs)后分别行6级迭代算法薄层重组.由2名放射医师采用双盲法读片并对图像质量做主观评分,记录CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP),计算辐射有效剂量(ED);测量图像的客观噪声值,计算信噪比,测量结石CT值及最大长径,记录结石检出数.结果 常规组:CTDIvol(23.51±0.79) mGy,DLP(1166.38±52.78)mGy·cm,ED(17.50±0.79)mSv;A组:CTDIvol(11.78±0.38) mGy,DLP(584.68±25.47) mGy· cm,ED(8.77±0.38) mSv;B组:CTDIvol(8.34±0.13)mGy,DLP(462.87±24.76) mGy· em,ED(6.94±0.37)mSv;C组:CTDIvol(5.47±0.21) mGy,DLP(268.20±19.03)mGy·cm,ED(4.02±0.29) mSv;各组低剂量迭代算法重组的iDose l ～6图像结石检出数、结石CT值及大小与常规剂量比较差异无统计学意义(P＞0.05);A组低剂量迭代算法重组的iDose4图像噪声(SD)、信噪比(SNR)及iDose 4—6图像质量主观评分与常规剂量比较差异无统计学意义(P＞0.05);B组低剂量迭代算法重建的iDose6图像噪声、信噪比及图像质量主观评分与常规剂量比较差异无统计学意义(P＞0.05);C组低剂量迭代算法重建的iDose l～6各组图像噪声、信噪比及图像质量主观评分与常规剂量比较差异有统计学意义(P＜0.05).结论 CT低剂量扫描联合迭代算法诊断输尿管结石是可行的,可以在不影响图像质量的前提下明显减低辐射剂量.管电压120 kV情况下,在iDose6水平管电流150mAs为最低临界扫描参数.     

自动管电流调节联合低电压低剂量扫描技术在幼儿胸部CT扫描中的优化应用研究

目的 探讨64层CT自动管电流调节技术(ATCM)结合低电压在幼儿胸部低剂量扫描中的应用价值.方法 搜集行64层CT ATCM胸部扫描的幼儿(≤2岁)48例,其中A组(管电压100 kV)30例,B组(管电压80kV) 18例;并与既往采用固定管电流条件下的低剂量扫描数据进行对比分析,对照组C组(100 kV/60 mAs)30例;其余扫描参数一致.记录每次扫描的平均管电流(mAs)、CT容积剂量指数(CTDIvol)、剂量长度值(DLP),计算出有效剂量(ED)及剂量减低比值(DR),并比较3组的剂量及图像质量.结果 A组CTDIvol为(1.11±0.19)mGy,B组CTDIvol为(0.99 ±0.11)mGy,C组CTDIvol为(2.38±0.00) mGy;3组数据两两比较差异均有统计学意义(P＜0.05).A组相对C组DR约51.07％,B组相对C组DR降低约58.20％.3组图像质量均满足诊断要求,差异无统计学意义(P=0.50).结论 低电压联合ATCM技术在幼儿胸部扫描中可以广泛应用,能够有效降低辐射剂量且不影响图像质量.     

多层螺旋CT膝关节低剂量扫描对影像质量的影响

目的:探讨多层螺旋CT低剂量膝关节扫描的可行性及其对图像质量的影响。方法:收集2009年5月~10月,100例行膝关节CT扫描者根据扫描的管电压高低分为2组(其他扫描条件不变),每组50例,A组110kV和B组80kV(管电压选择110kV和80kV是依据分别观察10例在此条件下扫描的患者图像,应用80kV而不影响诊断)。测量膝关节髌骨上缘水平后方肌肉软组织固定ROI的CT值,以CT值的标准差(SD)作为图像噪声。通过CT机自动得到平均容积CT剂量指数(CTDIvol),再计算出剂量长度乘积(DLP)。获得的图像通过双盲法进行质量评分,对两组CTDIvol值、DLP值、图像噪声、及图像质量评分均值用t检验进行比较。结果:A组和B组的CTDIvol值分别为(5.29±0.23)和(2.08±0.15)mGy,DLP值分别为(61.26±11.64)和(24.21±4.64)mGy.cm,B组较A组下降约(60.68)%,两者之间差异均有统计学意义(t值分别为(82.4)和(20.91),P0.01,B组噪声均值略高于A组(分别为12.22±2.97和16.55±2.96),t=-7.299,P=0.000,但两组图像质量平均评分分别为(4.86±0.40)分和(4.82±0.44)分,差异无统计学意义(t=0.475,P0.05)。结论:16层螺旋CT应用低kV设置(80kV)扫描膝关节可大幅度降低辐射剂量且所得图像质量不影响诊断。     

不同管电流VHRCT在肺部健康体检中的应用

目的探讨不同管电流低剂量容积数据高分辨率CT(VHRCT)在肺部健康体检中的应用价值。方法选取我院进行体检的3356例健康人作为观察对象,按照随机数字表法分为低剂量组(n=1678,120kV、50mA)、对照组A (n=839,120kV、100mA)、对照组B(n=839,120kV、150mA),观察比较三种不同剂量螺旋CT对肺部疾病的检查结果及图像质量。结果三组肺部疾病检出率及各肺部病变征象评分基图像质量间差异无统计学意义(P0.05);低剂量组的DLP为(157.66±23.71)mGy.cm、CTDIvol(3.22±0.57)mGy,均显著低于对照组A的[(439.83±45.94)mGy.cm、(9.38±1.19)mGy]及对照组B的[(443.42±46.87)mGy.cm、(9.42±1.23)mGy],差异有统计学意义(P0.05)。结论采用120kV和50mA的VHRCT诊断肺部疾病,射剂量减少而且能得到与常规剂量相同的图像质量。     

Automatic Tube Current Regulation Technique for the Evaluation of Aortic Dissection and Postoperative Radiation Dose

目的 探讨64排螺旋CT(MSCT),采用固定噪声指数(NI)的Z轴自动管电流调节(ATCM)技术在主动脉夹层术后CT造影中对图像质量及辐射剂量的影响.资料与方法 随机将本院主动脉夹层术后的患者100例分为2组,每组50例.A组采用固定管电流扫描技术,均采用280 mA.B组采用Z轴ATCM扫描技术,管电流为100～350 mA,根据体重指数(BMI)不同分为两组:BMI＞ 25 kg/m2者,NI=10;BMI ＜25 kg/m2者,NI =12,其余扫描参数均一致.将所有图像均传输至ADW 4.3工作站,进行三维及二维后处理,同时记录机器自动生成的CT剂量指数(CTDlvol)、相应剂量长度乘积(DLP).结果 B组在不影响诊断的情况下,辐射剂量较A组CTDIvol降低了28.3％、DLP降低了 30.4％.A组CTDIvol均值为(19.13±1.94) mGy;DLP均值为(1205.59±197.12) mGy·cm,B组BMI＞ 25 kg/m2者CTDIvol均值为(14.82±2.97) mGy; DLP均值为(887.6±177.51) mGy·cm,BMI＜ 25kg/m2者CTDlvol均值为(12.61±2.17)mGy; DLP均值为(789.86±139.33) mGy·cm,所有图像均能满足诊断需要.结论 64排螺旋CT采用固定NI的ATCM技术在主动脉夹层CT造影中可获得较好图像质量,在满足诊断需求的同时降低了患者辐射剂量.     

自动管电流调节技术对主动脉夹层术后的评价及其辐射剂量的研究

目的探讨64排螺旋CT(MSCT),采用固定噪声指数(NI)的Z轴自动管电流调节(ATCM)技术在主动脉夹层术后CT造影中对图像质量及辐射剂量的影响。资料与方法随机将本院主动脉夹层术后的患者100例分为2组,每组50例。A组采用固定管电流扫描技术,均采用280 mA。B组采用Z轴ATCM扫描技术,管电流为100～350 mA,根据体重指数(BMI)不同分为两组:BMI>25 kg/m2者,NI=10;BMI<25 kg/m2者,NI=12,其余扫描参数均一致。将所有图像均传输至ADW 4.3工作站,进行三维及二维后处理,同时记录机器自动生成的CT剂量指数(CTDlvol)、相应剂量长度乘积(DLP)。结果 B组在不影响诊断的情况下,辐射剂量较A组CTDlvol降低了28.3%、DLP降低了30.4%。A组CTDIvol均值为(19.13±1.94)mGy;DLP均值为(1205.59±197.12)mGy.cm,B组BMI>25 kg/m2者CTDIvol均值为(14.82±2.97)mGy;DLP均值为(887.6±177.51)mGy.cm,BMI<25kg/m2者CTDIvol均值为(12.61±2.17)mGy;DLP均值为(789.86±139.33)mGy.cm,所有图像均能满足诊断需要。结论 64排螺旋CT采用固定NI的ATCM技术在主动脉夹层CT造影中可获得较好图像质量,在满足诊断需求的同时降低了患者辐射剂量。     

埋伏阻生牙64排螺旋CT低剂量扫描的应用价值

目的:探讨64排螺旋CT低剂量扫描对颌骨埋伏阻生牙的应用价值。方法:对80例埋伏阻生牙的患者行64排螺旋CT检查,根据管电流分为200、100、50和20mA四组,对原始图像进行多平面重建(MPR)、容积成像(VR)、曲面重建、齿科软件重建及最大密度投影(MIP),对不同扫描参数的图像质量进行评价,记录CT剂量指数(CTDIvol)和剂量长度乘积(DLP),并进行统计学分析。结果:①100mA组、50mA组图像质量均可满足临床诊断要求,但与200mA组评分差异均有统计学意义(P<0.05)。②100mA组、50mA组的CTDIvol分别为11.67和5.84mGy,DLP分别为58.59和29.30mGy.cm,100mA、50mA组CTDIvol、DLP分别较200mA组下降约50%和75%。结论:颌骨埋伏阻生牙64排螺旋CT低剂量扫描图像质量有所下降,但能满足临床诊断需要,辐射剂量明显下降。     

64层螺旋CT低剂量扫描技术在骶髂关节病变中的应用

目的探讨64层螺旋CT低剂量扫描技术在骶髂关节病变中的应用。资料与方法对1000例临床拟诊为骶髂关节病变的患者行64层螺旋CT检查,分为常规剂量组 220mAs和使用Care Dose 4D技术低剂量组,每组各500例。由2位有经验的放射学医师采用双盲法阅片评价图像质量并做出第一次CT诊断,3个月后重新阅片并做出第二次CT诊断,分析两种扫描模式的CT剂量指数(CTDIvol)、图像质量及前后两次CT诊断结果的差异。结果常规剂量组及低剂量组的CTDIvol分别为18.9±0.0mGy及5.9±0.8mGy,低剂量组平均CTDIvol较常规剂量组降低68.8%;常规剂量组及低剂量组图像评分分别为3.7±0.5分及3.6±0.6分,前后两次CT诊断结果符合率分别为97.7%(166/170)及95.2%(178/187),两组之间的图像评分及前后两次CT诊断结果差异均无统计学意义(P> 0.05)。结论 64层螺旋CT低剂量扫描适用于骶髂关节病变的检查,有利于受检者生殖腺的辐射防护。     

螺距对下肢CTA辐射剂量与图像质量影响的研究

目的探讨MSCT螺距对下肢CTA辐射剂量与图像质量的影响。资料与方法收集临床拟诊为下肢动脉疾病的患者60例,按不同螺距随机分成3组进行扫描,A组:1.375;B组:0.984;C组:0.516。扫描结束后记录CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP)。对3种螺距扫描的图像质量、辐射剂量和扫描总时间(To-time)采用方差检验(F)进行统计学分析。结果 A、B、C3组单次扫描CT剂量加权指数分别是14.94mGy、20.87mGy、39.83mGy;DLP分别为1698.75±74.78mGy/cm、2331.87±62.62mGy/cm、4485.69±205.00mGy/cm,3组差异有统计学意义(P<0.05),A组辐射剂量最低,C组辐射剂量最高。3种螺距扫描所获得的图像质量评分分别是3.55±0.40、3.67±0.28、3.66±0.32,差异无统计学意义(P>0.05);3组扫描总时间分别是12.34±0.54、17.04±0.44、32.78±1.49,差异有统计学意义(P<0.05),大螺距扫描所用时间最短。结论采用螺距为1.375的扫描可减少病人的辐射剂量,且图象质量较好,可满足临床诊断。     

Principles of CT: multislice CT

This article describes the principles and evolution of multislice CT (MSCT), including conceptual differences associated with slice definition, cone beam effects, helical pitch, and helical scan technique. MSCT radiation dosimetry is described, and dose issues associated with MSCT-and with CT in general-as well as techniques for reducing patient radiation dose are discussed. Factors associated with the large volume of data associated with MSCT examinations are presented.     

Principles of CT and CT technology

This article provides a review of the basic principles of CT within the context of the evolution of CT. Modern CT technology can be understood as a natural progression of improvements and innovations in response to both engineering problems and clinical requirements. Detailed discussions of multislice CT, CT image quality evaluation, and radiation doses in CT will be presented in upcoming articles in this series.     

PET/CT in malignant melanoma: contrast-enhanced CT versus plain low-dose CT

Purpose  

The aim of this study was to evaluate the diagnostic value of contrast-enhanced CT (CECT) versus non-enhanced low-dose CT (NECT) in the staging of advanced malignant melanoma with ¹⁸F-fluordeoxyglucose (FDG) positron emission tomography (PET)/CT.     

CT angiography

The advent of spiral (helical, volume ) CT has revolutionised the performance of body CT and allowed the development of CT angiography (CTA). CT angiography is a non-invasive method of visualising the vascular system and in some instances can replace conventional angiography. In spiral CT a volume of data is obtained rapidly with no respiratory misregistration at peak vascular opacification following the peripheral injection of contrast. Appropriate timing will ensure that either the venous or arterial tree is visualised and from the volume of data multiple overlapping slices can be obtained to generate 2D and 3D images with no increase in radiation to the patient. CT angiography may be performed as a dedicated study or be undertaken retrospectively using post-processing of data from a conventional diagnostic spiral scan to provide additional information about the vascular tree. When undertaken as a dedicated study CTA is quicker, less invasive and less costly than a conventional angiogram with a decrease in the radiation dose to the patient; however, the spatial resolution is limited with vessels less than 2 mm not visualised and there is no contrast saving. Received: 25 March 1998; Revision received: 16 July 1998; Accepted: 22 July 1998     

CT扫描参数对人体组织CT值影响的研究

目的 探索不同CT扫描参数对人体同一种组织CT值的影响。方法 通过在同一台CT机上,分别改变其中1个扫描参数,如X线管电压、毫安秒和重建函数等,而保持其他扫描参数不变,多次扫描标准体模,测量和分析体模中不同物质的CT值。结果 X线管电压的改变对物质的CT值影响具有显著意义。聚乙烯、聚碳酸酯、有机玻璃的CT值与管电压成正相关;聚四氟乙烯的CT值与管电压成负相关。毫安秒和重建函数对CT值的影响差异无统计学意义。结论 同一个人体组织在不同的X线管电压条件下CT值是变化的。因此,在临床影像诊断和放疗中应该考虑图像扫描参数的设置对诊断和治疗结果的影响。     

Limitations of CT during PET/CT.

Our aim was to determine the diagnostic limitations of low-dose, unenhanced CT scans performed for anatomic reference and attenuation correction during PET/CT. METHODS: The Radiology Information System at our oncologic hospital was queried during the 9-mo period from July 2002 to April 2003 for patients with PET/CT scans and diagnostic enhanced CT within 2 wk of each other. One radiologist interpreted the CT portion of the PET/CT (CT(p)) unaware of the PET results and the associated enhanced diagnostic CT (CT(d)). A medical student compared this interpretation with the official report of the CT(d) and listed all discrepancies between reports. A separate radiologist compared CT(p) and CT(d) images and classified true discrepant findings as due to lack of intravenous contrast, arm-position artifact, lack of enteric contrast, low milliamperage (mA), and quality of lung images. RESULTS: Among 100 patients, the most common malignancies were lymphoma (n = 37), cancer of the colorectum (n = 31), and esophageal cancer (n = 15). Among 194 true discrepancies in which findings were missed at CT(p), causes were as follows: (a) lack of intravenous contrast (128/194, 66%), (b) arm-down artifact (17/194, 9%), (c) quality of lung images (26/194, 13%), (d) lack of enteric contrast (15/194, 8%), and (e) low mA (8/194, 4%). Discrepancies were seen most commonly in detecting lymphadenopathy and visceral metastases. CONCLUSION: Most missed findings on the unenhanced CT portion of the PET/CT scans were due to technical factors that could be altered. Discrepant findings would have led to altered management in only 2 patients, suggesting a role for limited repeat imaging to reduce radiation and use of valuable resources.     

Multidetector CT and CT angiography in mesenteric ischemia

Purpose

To evaluate the role of 64-multidetector CT in assessment of mesenteric vascular ischemia in clinically suspected patients.

Patients and methods

This study included 38 patients during period from October 2009 to October 2011. The patients age ranged from 38 to 72 year old (mean age was 57 ± 11.2 years). All cases met the criteria of acute non traumatic (28 patients) or chronic abdominal pain (10 patients) and suspected mesenteric vascular ischemia. All 38 cases were evaluated in surgery department, then underwent CT of the abdomen and pelvis & CTA by using 64 multislice GE light speed VCT. MDCT& CT angiographic findings were correlated with surgical findings in acute mesenteric ischemia (AMI) cases & conventional angiography in chronic mesenteric ischemia (CMI) cases.

Results

MDCT findings alone were nonspecific for detection of MI. The sensitivity, specificity& accuracy of CTA in diagnosis of AMI after surgical confirmation were 96%, 66.6% & 92.8% respectively, while in CMI the sensitivity, specificity & accuracy were 88.8%, 100%, 90% respectively, after confirmation by conventional angiography.

Conclusion

CTA scan appears to be an excellent tool to find out and localize cases of AMI rather than in CMI cases.