宝石CT低剂量扫描结合ASIR重建小肠造影的临床研究
摘要
背景和目的：
小肠占胃肠道全长的约四分之三,上接胃窦幽门口,下达回肠远端回盲部,是人体消化食物、营养吸收的最重要场所。小肠疾病也是很常见的,有的为肠道原发疾病,有的继发性疾病,一旦小肠出现不适病症,就会引起消化道各种表现及营养吸收障碍,有些原发疾病甚至可以引起全身其他系统的一系列相关症状。随着人民生活水平的提高以及人们工作、生活习惯及饮食结构的变化,胃肠道疾病呈不断上升的趋势,小肠疾病发病率也在提高。但是小肠冗长并相互折叠的生理及解剖特点,造成小肠疾病检查诊断方法相对缺乏,在影像诊断上,小肠疾病的检查也一直是一个盲点。常见的小肠诊断方法主要有口服钡剂小肠造影、小肠气钡双重对比造影、MRI小肠造影、多排螺旋CT小肠造影法等影像学检查方法,目前临床上还有双气囊小肠镜和小肠胶囊内镜,各种检查方法自有利弊。本课题主要采用多层螺旋CT小肠造影法对小肠疾病进行诊断,以观其效。但是常规小肠造影需要做全腹部扫描,因此有效辐射剂量较大,每个体位最高可达11.7mSv(单序列扫描),另外,为了提高阳性病变显示的敏感性和特异性,提高病变的检出率,小肠CT造影检查时常常需要进行全腹部双期甚至三期扫描(平扫加多期增强),这无疑进一步增加了扫描辐射剂量,且关于电离辐射之剂量问题近年来也越来越为人所关注。所以本课题选取正常体重指数以内,临床怀疑小肠疾病患者及部分健康体检受检者为对象,展开对宝石CT低剂量扫描小肠造影的研究,并结合其最新的自适应迭代数据重建技术ASIR(Adaptive Statistical Iterative Reconstruction)技术,旨在探讨该法在小肠疾病的诊断价值及腹部(小肠)低剂量方面的临床意义。该研究的主要目的是探讨宝石CT低剂量扫描结合ASIR重建在小肠CT造影的临床应用价值。
材料和方法：
(1)一般资料
选取自2011年4月至2012年3月之间在我院住院或者门诊检查怀疑小肠疾病的患者随机分为三组(A、B、C),并进行全腹部CT检查的患者120例(男71女49,年龄16-78岁,平均39.7岁)；其中A组患者年龄平均(40.8±15.4岁),B组患者年龄平均(37.6±14.1岁),C组患者年龄平均(36.9±16.8岁)。A组为常规剂量扫描,B、C两组为试验组,分别进行低剂量扫描。纳入本课题所有患者体重指数(body mass index, BMI=体质量/身高2)均<25Kg/m2。所有患者均无静脉团注造影剂增强扫描之禁忌症,并接受HDCT小肠造影检查,完成整个扫描检查过程。
(2)造影扫描前患者准备
检查前两天,告知所有受检者需低脂肪、低纤维、流质饮食,检查前8-12小时禁食、口服缓泻剂。询问病人过敏史,有青光眼病史、前列腺肥大等症及排尿困难者禁用山莨菪碱注射液。
(3)仪器设备及扫描方法
采用GE宝石CT (Discovery 750HD)机型,扫描范围从膈顶至耻骨联合。扫描技术参数采用固定噪声指数,固定管电压120KVP,自动毫安范围(100—600mA),螺距1.375：1,准直器宽度64×0.625mm。不同组别噪声(noise index,NI)设定分别为：A、B、C三组噪声NI分别预设为9、12、14；其中A组采用常规剂量扫描,B组和C组采用低剂量扫描,在原始扫描数据的基础上,分别将B组患者图像采用50%ASIR重建、C组患者的图像采用70%ASIR重建分别得到两组不同的图像,记做Bs0、C70重建层厚5mm,间隔5mm。
扫描序列为平扫加动脉期及静脉期双期增强,经肘静脉以3.5ml/s注射碘海醇非离子型对比剂100ml/瓶,剂量1.5ml/kg。注射造影剂后待主动脉CT值达200HU触发扫描,一般25s-30s；在动脉期基础上延迟40s行静脉期扫描,一般65-70s。回顾性分析图像层厚为0.625mm,在ADW4.4工作站上进行必要的多项后处理重建,例如多平面重建(Multi Planar Reformation、最大密度投影(Maximum Intensity Projection, MIP)和容积重建(Volume Rendering, VR),以满足诊断需要。
(4)图像质量评价
主观评价：将各组图像包括重建图像传输至PACS,屏蔽患者所有扫描参数及相关信息。对于同一患者分别选择同一层面不同重建序列比较其图像质量,对于不同患者选择近似层面比较其图像质量,为保证选取感兴趣区一致性,肝实质均选择第二肝门处,小肠及肠周脂肪图像监测选择腰1椎体水平。应用固定标准腹部窗宽、窗位。由2名资深放射科医师采用量化评分制度独立对图像质量进行评判,对于疾病诊断,若双方意见有分歧时,通过协商,达成一致。基于解剖结构量化评估图像质量,观察腹部实质脏器(肝脏)、小肠粘膜、小肠壁显示情况、肠周脂肪及肠系膜血管的结构清晰度及噪声。对图像质量以5分制进行评分：不合格,完全不能满足诊断要求为1分；较差、能满足诊断基本要求,但不能满足鉴别诊断需要为2分；一般、能满足诊断要求为3分；良好、能满足诊断要求为4分；优秀、能满足诊断要求为5分。量化评分≥3分的被认为图像质量可以满足临床需要。
客观评价：测量各组肝、脾实质及肠系膜脂肪感兴趣区(ROI:100mm2)CT值及其标准差,以标准差代替图像客观噪声(SD),并计算信噪比(SNR)、对比信噪比(CNR)。对所得数据资料进行相应的统计学分析。
(5)辐射剂量：
分别记录3组患者所接受的辐射参数：容积CT剂量指数(CT dose index voulme,CTDIvol)、剂量长度乘积(dose length product,DLP)由机器自动计算生成,并估算有效剂量(Effective Dose,ED),计算公式ED=DLPX0.015。
(6)统计学方法：
采用SPSS17.0统计软件,计量资料均以x±s表示。统计学上对A、B、B50、C、C705组之间CT值、噪声(SD)、信噪比(SNR)、对比信噪比(CNR)组间差异采用单因素方差分析或Kruskal-Wallis秩和检验,各组测量指标均数之间两两比较采用LSD-t检验或Bonferonni校正检验；对于B、C两组进行ASIR重建之后图像分别于两组原始图像之间CT值、噪声(SD)、信噪比(SNR)、对比信噪比(CNR)组间差异对比采用独立样本t检验；对于A、B、C三组间年龄、体重指数(BMI)、CT剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效剂量(ED)测量数据指标差异采用单因素方差分析；两名医师采用5分制对图像质量进行评估,并用Kappa检验评价观察者间的一致性,≧0.75代表一致性较好,0.4—0.75代表一致性一般,<0.75说明一致性较差。
结果：
(1)三组患者的平均身高、体重指数差异无统计学意义(P>0.05)。三组原始图像优良程度评分组间对比存在差异,两两比较A组和B组、A组和C组、B组和C组差异均有统计学意义。而A组和重建后的两组图像B50、C70组间两两比较差异无统计学意义,且评分结果显示均能满足诊断需要。5组之间对比噪声(SD)、信噪比(SNR)、对比信噪比(CNR)组间对比均有差异,两两比较A组和B组间、A组和C组间、B组和C组间差异均有统计学意义,而A组、B50和C70组组间两两比较差异无统计学意义。5组图像数据显示C组噪声最大,其次为B组,A组噪声最小；A组SNR及CNR值最高。A组的CTDIvo1为(14.07±2.19)mGy,B组CTDIvol为(9.13±2.11)mGy,C组CTDIvol为(6.64±0.94)mGy,三组数据显示各组受检者所接受有效辐射剂量明显不同,且组间两两比较差异有统计学意义。B组较A组(CTDIvol)和剂量长度乘积(DLP)分别减少了35.11%和34.23%,C组减少的更多,分别为52.81%和56.08%。
(2)在对图像质量的主观评分中,两名医师对A组、B50组和C70组的评价结果显示均能满足临床诊断需求,两名医师对三组图像评价的一致性中等(平均Kappa值为0.469)。伴随NI值的增高,放射剂量的减低,A组、B组、C组三组图像质量评分依次下降,其中A组评分最高,C组评分最低(肝实质评分为2.7)。选取不同感兴趣区的评分差异也各不相同,实质脏器的评分结果看,B、C两组较A组得分下降明显,而对小肠肠壁、肠系膜脂肪及肠系膜血管的显示B、C两组得分较A组得分也有所减低,但程度没有肝脏、脾脏等实质脏器减低明显。对经ASIR重建的B50组和C70组的图像质量评分较A组均相差无几。
(3)所有受检者小肠CT造影显示阳性结果共78例,其中感染性疾病最多21例,肿瘤及肿瘤样病变19例,血管瘤及血管性病变9例,淋巴瘤7例,肠道憩室5例,另结肠占位7例,肝腺瘤1例,轻度肠梗阻3例,直肠癌2例,降结肠淋巴瘤、腹膜腔内恶性间叶组织肿瘤、结肠癌伴肝实质多发转移、腹腔内多发小间质瘤各1例。
结论：
(1) HDCT可以在获得稳定图像质量的同时,大幅度降低扫描辐射剂量。
(2) ASIR重建技术在低剂量扫描同时,能充分起到降低噪声,抑制伪影,提高图像质量的作用。
(3)不同ASIR重建值对图像的噪声水平改变不同。
Background and Purpose:
Samall intestine is the longest part of the digestine tract, and its accounted about 75% of the total length of the gastrointestinal tract,and its Starting at the antrum secluded entrance, issued the ileum distal to the ileocecal junction.the most important places for human food digestion and nutrient absorption of various digestive juices in the small intestine in chymedecomposition, afterdigestion and absorption of residues excreted. Small intestinal disease is very common, some were intestinal primary disease, and some were secondary disease. Once the small intestine diseases, It can cause digestion and absorption barriers, some of the primary disease can even cause other systems of the body a series of related symptoms. With the improvement of living standards of the people and the way people work, life style and dietary changes in the structure, gastrointestinal diseases showed a rising trend, the small intestine disease incidence is also increasing. But the lengthy small intestine and mutual folding of the physiological and anatomical characteristics, the cause of small bowel diseases diagnosis method is relatively scarce, and in the diagnostic of imaging, the inspection of small bowel diseases has been a blind spot. There are several common intestinal diagnostic methods such as oral barium small bowel imaging,small bowel barium double contrast small bowel magnetic resonance imaging, MRI and multislice spiral CT enterography imaging methods, In recent years, the clinical use other methods, such as double balloon enteroscopy and small bowel capsuleits own advantages and disadvantages of endoscopy, a variety of inspection methods. The main subject of multislice spiral CT enterography imaging method is to diagnose the small bowel disease, in order to observe its effect. Conventional small bowel contrast need to do the whole abdomen scan, so the effective radiation dose for each position up to 11.7 mSv, (single serial scan), On the other hand in order to increase the sensitivity and specificity of the lesions showed increase in the detection of positive lesions rate, small intestine CT angiography is often necessary for dual-phase or three scanning of the whole abdomen (unenhanced added enhancements), which will undoubtedly further increase the scanning radiation dose. And the dose of ionizing radiation in recent years has more and more attentionned for human. So my topic select whom body mass index in less than normal, and clinical suspicion of intestinal diseases and some people do healthy subjects, expand the small intestine contrast study with Gem CT low-dose scanning, combined with the latest iteration of the Adaptive Statistical Iterative Reconstruction technology (ASIR) technology designed to explore the clinical value of small bowel disease with the low dose scanning.
Materials and methods:
(1)General Information
Select 120 patients(male71 49 female, age 16-78 years old, average 39.7 years) from April 2010 to March 2011 in our hospital or outpatient who visits in patients and suspected has small bowel disease and randomly divided them into three groups (A, B, and C), And all of them made full abdominal CT scanning, The average age of group A patients (40.8±15.4Y), group B patients with average age (37.6±14.1 Y), group C patients with average age (36.9±16.8Y)). Group A conventional-dose scan, B and C the two groups for the experimental group, respectively, take low-dose scan. All patients included in this subject body mass index (body mass index, BMI= body mass/height 2)<25Kg/m2. All patients had no intravenous bolus injection of contrast agent to enhance scans contraindications, and accept the HDCT small bowel imaging, to complete the entire scanning process.
(2) Prepare in advance
Two days before the test, all patients with small bowel imaging needs of low-fat, low fiber, liquid diet, check the first 8-12 hours of oral laxatives, fasting before the test meal. Ask the patient a history of allergies, Patients who have a history of glaucoma, prostatic hypertrophy, embolism, and dysuria were banned intramuscular injection of hydrochloric acid 654-2 injection, the patient if the symptoms of acute intestinal obstruction can not oral contrast to those who do not do this check.
(3) Equipment and scanning methods
With GE gem CT (Discovery 750HD) models, scan range from the top of diaphragm to the pubic symphysis. Scanning technical parameters fixed noise index, a fixed tube voltage 120KVP, automatic mA range (100-600mA), pitch 1.375:1, collimator width of 128 X 0.625mm. Different groups of noise (noise index, NI) settings are as follows:A, B, C noise NI by default 9,12,14; in group A with conventional-dose scan, group B and group C with low-dose scan, on the basis of the original scan data, respectively, an image of the group B patients with 50% ASIR reconstruction image of the group C patients with 70% ASIR reconstruction, respectively, two different sets of images, denoted B50 is C70, reconstruction slice thickness 5mm, interval of 5mm.
The sweep of the scanning sequence level plus dual-phase enhanced scan, the cubital vein injection of nonionic contrast agent to 3.5 ml/s,100ml/bottle, dose 1.5ml/kg. After injection, aortic CT value 200HU automatically trigger the arterial phase scan (diagnostic delay time 5s), generally 25s～30s; 40s vein phase scans in the arterial phase on the basis of delay, usually 65～70s. Retrospective image slice thickness 0.625mm, ADW4.4 workstation deal with reconstruction after the necessary number of, for example, multi-planar reconstruction (Multi Planar's Reformation MPR), maximum intensity projection (Maximum of Intensity Projection is the MIP) and volume rendering (Volume Rendering, VR), in order to meet the diagnostic needs.
(4) Image quality
Subjective evaluation:Each set of images includding the reconstructed image transmitted to the PACS, shielding every patients all scan parameters and related information. Respectively choose the same level reconstruction sequence to compare the image quality for the same patient, Select the approximate level of comparison for different patients, For example,the liver parenchyma select the second hepatic hilum, small intestine and intestinal fat image monitoring select the waist 1 vertebral level. A fixed standard abdominal window width and window level. Be judged on image quality by 2 independent senior radiologists for disease diagnosis, differences of opinion, through consultation, to reach agreement. Quantitative evaluation of image quality based on the anatomical structure, the observation of abdominal parenchymal organs (liver), the small intestinal mucosa, small intestine showed the structural clarity and noise of the intestinal weeks fat and mesenteric vessels. On image quality with a 5-point rating:unqualified, can not meet the diagnostic requirements for 1 minute; less able to meet the diagnosis of the basic requirements, but can not satisfy the differential diagnosis of the need for 2 minutes; in general, to meet the diagnostic requirements for 3 minutes; good to meet the diagnostic requirements for 4 minutes; outstanding, to meet the diagnostic requirements for 5 minutes. Quantitative score of≥3 points was considered the image quality to meet the clinical needs.
Objective evaluation:measurement of each group of the liver, spleen substance and mesenteric fat regions of interest (of VOI:100mm2) CT value and its standard deviation, standard deviation instead of the objective image noise (SD), and calculate the signal-to-noise ratio (SNR), contrast letter noise ratio (CNR). Appropriate statistical analysis of the obtained data.
(5) The radiation dose:
Recorded three groups of patients received radiation parameters:volumetric CT dose index (CT dose index voulme, CTDIvol), dose-length product (a dose length product, DLP) is generated by the machine automatically calculate and estimate the effective dose (Effective Dose, the, ED), the formula ED=DLPX0.015.
(6) Statistical methods:
Use SPSS 17.0 statistical software, measurement data are expressed(x±s).The difference between the groups A, B, B50, C, C70 set of CT values, the noise (SD) signal-to-noise ratio (SNR), contrast to noise ratio (CNR) using single-factor analysis of variance or Kruskal-Wallis rank sum test, The measure between the number of pairwise comparisons of LSD-t test or Bonferonni correction test; The B、C and B50. C70 between the two sets of the original image, noise (SD the differences between groups comparison), the signal-to-noise ratio (SNR), contrast to noise ratio (CNR) using independent samples t test; About A、B、C three groups of age, body mass index (BMI), CT dose index (CTDIvol) dose length product (DLP), the effective dose (ED) measurement data indicators of differences in the single factor analysis of variance; Two physicians using a five-point scale to assess the image quality and consistency in the evaluation of interobserver Kappa test,≥0.75 on behalf of consistent good,0.4-0.75 on behalf of the consistency,and<0.75 is less consistently.
Results:
(1) three groups of patients, the average height, body mass index were no significant differences (P> 0.05). Contrast between the three groups of the original image excellent score group differences, pairwise comparisons of group A and group B, group A and group C, group B and group C there were significant differences. No significant pairwise differences between the two sets of images in group A and re-B50, C70 group, and the score results can meet the diagnostic needs. Contrast to noise (SD) between the signal-to-noise ratio (SNR), contrast to noise ratio (CNR) contrast were different between groups, pairwise comparisons of group A and group B, group A and group C, group B and the difference between group C were statistically significant, but no significant pairwise differences between group A, B50 and C70 group group. The image data group C noise, group A SNR and CNR values. Group A CTDIvol (14.07±2.19) of mGy, CTDIvol Group B (9.13±2.11) of mGy, CTDIvol group C (6.64±0.94) of mGy between the two groups statistically significant pairwise differences. Group B compared with group A (CTDIvol) and dose length product (DLP) were reduced by 35.11% and 34.23%, Group C reduced more for 52.81% and 56.08%, respectively.
(2) the subjective rating of image quality, the two physicians'evaluation of group A, B50, and C70 group results can meet the clinical diagnostic needs, two physicians three sets of image evaluation of the consistency of medium (average Kappa value of 0.469). Accompanying NI values increased, the reduction of radiation dose, group A, group B, group C, three sets of image quality score, followed by decline in group A, the highest scores, group C the lowest score (liver parenchyma score of 2.7). Select a different region of interest of the differences in scores of the same score in the substance of the liver, spleen and other organs results of B, and C group compared with group A score significantly decreased, while the small intestine, the intestinal wall, mesenteric fat and mesenteric vessels display B, C, two sets of score compared with group A score has also been reduced, but the degree does not reduce significantly the substance of the liver, spleen and other organs. Image quality rating by the the ASIR renewal B50 group and the C70 group compared with group A are almost the same.
(3) the small intestine of all subjects with CT angiography showed positive results of 78 cases, of which up to 21 cases of infectious diseases, tumors and tumor-like lesions of 19 cases,9 cases of vascular tumors and vascular lesions,7 cases of lymphoma, intestinal diverticula 5 cases of colon placeholder eight cases, liver adenoma, intestinal obstruction in three cases, two cases of rectal cancer, descending colon, lymphoma, colon cancer with liver parenchyma multiple transfer one cases, multiple intra-abdominal small stromal tumors one cases.
Conclusion:
(1) HDCT can in a stable image quality at the same time, greatly reduce scanning radiation dose.
(2) ASIR Adaptive Statistical Iterative Reconstruction technology can reduce the noise rise adequately, restrain the artifact, improve the quality of image when the low doses scanning were taken.
(3) Different ASIR reconstruction make the different value of the noise level for the image change.
小肠占胃肠道全长的约四分之三,上接胃窦幽门口,下达回肠远端回盲部,是人体消化食物、营养吸收的最重要场所。小肠疾病也是很常见的,有的为肠道原发疾病,有的继发性疾病,一旦小肠出现不适病症,就会引起消化道各种表现及营养吸收障碍,有些原发疾病甚至可以引起全身其他系统的一系列相关症状。随着人民生活水平的提高以及人们工作、生活习惯及饮食结构的变化,胃肠道疾病呈不断上升的趋势,小肠疾病发病率也在提高。但是小肠冗长并相互折叠的生理及解剖特点,造成小肠疾病检查诊断方法相对缺乏,在影像诊断上,小肠疾病的检查也一直是一个盲点。常见的小肠诊断方法主要有口服钡剂小肠造影、小肠气钡双重对比造影、MRI小肠造影、多排螺旋CT小肠造影法等影像学检查方法,目前临床上还有双气囊小肠镜和小肠胶囊内镜,各种检查方法自有利弊。本课题主要采用多层螺旋CT小肠造影法对小肠疾病进行诊断,以观其效。但是常规小肠造影需要做全腹部扫描,因此有效辐射剂量较大,每个体位最高可达11.7mSv(单序列扫描),另外,为了提高阳性病变显示的敏感性和特异性,提高病变的检出率,小肠CT造影检查时常常需要进行全腹部双期甚至三期扫描(平扫加多期增强),这无疑进一步增加了扫描辐射剂量,且关于电离辐射之剂量问题近年来也越来越为人所关注。所以本课题选取正常体重指数以内,临床怀疑小肠疾病患者及部分健康体检受检者为对象,展开对宝石CT低剂量扫描小肠造影的研究,并结合其最新的自适应迭代数据重建技术ASIR(Adaptive Statistical Iterative Reconstruction)技术,旨在探讨该法在小肠疾病的诊断价值及腹部(小肠)低剂量方面的临床意义。该研究的主要目的是探讨宝石CT低剂量扫描结合ASIR重建在小肠CT造影的临床应用价值。
材料和方法：
(1)一般资料
选取自2011年4月至2012年3月之间在我院住院或者门诊检查怀疑小肠疾病的患者随机分为三组(A、B、C),并进行全腹部CT检查的患者120例(男71女49,年龄16-78岁,平均39.7岁)；其中A组患者年龄平均(40.8±15.4岁),B组患者年龄平均(37.6±14.1岁),C组患者年龄平均(36.9±16.8岁)。A组为常规剂量扫描,B、C两组为试验组,分别进行低剂量扫描。纳入本课题所有患者体重指数(body mass index, BMI=体质量/身高2)均<25Kg/m2。所有患者均无静脉团注造影剂增强扫描之禁忌症,并接受HDCT小肠造影检查,完成整个扫描检查过程。
(2)造影扫描前患者准备
检查前两天,告知所有受检者需低脂肪、低纤维、流质饮食,检查前8-12小时禁食、口服缓泻剂。询问病人过敏史,有青光眼病史、前列腺肥大等症及排尿困难者禁用山莨菪碱注射液。
(3)仪器设备及扫描方法
采用GE宝石CT (Discovery 750HD)机型,扫描范围从膈顶至耻骨联合。扫描技术参数采用固定噪声指数,固定管电压120KVP,自动毫安范围(100—600mA),螺距1.375：1,准直器宽度64×0.625mm。不同组别噪声(noise index,NI)设定分别为：A、B、C三组噪声NI分别预设为9、12、14；其中A组采用常规剂量扫描,B组和C组采用低剂量扫描,在原始扫描数据的基础上,分别将B组患者图像采用50%ASIR重建、C组患者的图像采用70%ASIR重建分别得到两组不同的图像,记做Bs0、C70重建层厚5mm,间隔5mm。
扫描序列为平扫加动脉期及静脉期双期增强,经肘静脉以3.5ml/s注射碘海醇非离子型对比剂100ml/瓶,剂量1.5ml/kg。注射造影剂后待主动脉CT值达200HU触发扫描,一般25s-30s；在动脉期基础上延迟40s行静脉期扫描,一般65-70s。回顾性分析图像层厚为0.625mm,在ADW4.4工作站上进行必要的多项后处理重建,例如多平面重建(Multi Planar Reformation、最大密度投影(Maximum Intensity Projection, MIP)和容积重建(Volume Rendering, VR),以满足诊断需要。
(4)图像质量评价
主观评价：将各组图像包括重建图像传输至PACS,屏蔽患者所有扫描参数及相关信息。对于同一患者分别选择同一层面不同重建序列比较其图像质量,对于不同患者选择近似层面比较其图像质量,为保证选取感兴趣区一致性,肝实质均选择第二肝门处,小肠及肠周脂肪图像监测选择腰1椎体水平。应用固定标准腹部窗宽、窗位。由2名资深放射科医师采用量化评分制度独立对图像质量进行评判,对于疾病诊断,若双方意见有分歧时,通过协商,达成一致。基于解剖结构量化评估图像质量,观察腹部实质脏器(肝脏)、小肠粘膜、小肠壁显示情况、肠周脂肪及肠系膜血管的结构清晰度及噪声。对图像质量以5分制进行评分：不合格,完全不能满足诊断要求为1分；较差、能满足诊断基本要求,但不能满足鉴别诊断需要为2分；一般、能满足诊断要求为3分；良好、能满足诊断要求为4分；优秀、能满足诊断要求为5分。量化评分≥3分的被认为图像质量可以满足临床需要。
客观评价：测量各组肝、脾实质及肠系膜脂肪感兴趣区(ROI:100mm2)CT值及其标准差,以标准差代替图像客观噪声(SD),并计算信噪比(SNR)、对比信噪比(CNR)。对所得数据资料进行相应的统计学分析。
(5)辐射剂量：
分别记录3组患者所接受的辐射参数：容积CT剂量指数(CT dose index voulme,CTDIvol)、剂量长度乘积(dose length product,DLP)由机器自动计算生成,并估算有效剂量(Effective Dose,ED),计算公式ED=DLPX0.015。
(6)统计学方法：
采用SPSS17.0统计软件,计量资料均以x±s表示。统计学上对A、B、B50、C、C705组之间CT值、噪声(SD)、信噪比(SNR)、对比信噪比(CNR)组间差异采用单因素方差分析或Kruskal-Wallis秩和检验,各组测量指标均数之间两两比较采用LSD-t检验或Bonferonni校正检验；对于B、C两组进行ASIR重建之后图像分别于两组原始图像之间CT值、噪声(SD)、信噪比(SNR)、对比信噪比(CNR)组间差异对比采用独立样本t检验；对于A、B、C三组间年龄、体重指数(BMI)、CT剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效剂量(ED)测量数据指标差异采用单因素方差分析；两名医师采用5分制对图像质量进行评估,并用Kappa检验评价观察者间的一致性,≧0.75代表一致性较好,0.4—0.75代表一致性一般,<0.75说明一致性较差。
结果：
(1)三组患者的平均身高、体重指数差异无统计学意义(P>0.05)。三组原始图像优良程度评分组间对比存在差异,两两比较A组和B组、A组和C组、B组和C组差异均有统计学意义。而A组和重建后的两组图像B50、C70组间两两比较差异无统计学意义,且评分结果显示均能满足诊断需要。5组之间对比噪声(SD)、信噪比(SNR)、对比信噪比(CNR)组间对比均有差异,两两比较A组和B组间、A组和C组间、B组和C组间差异均有统计学意义,而A组、B50和C70组组间两两比较差异无统计学意义。5组图像数据显示C组噪声最大,其次为B组,A组噪声最小；A组SNR及CNR值最高。A组的CTDIvo1为(14.07±2.19)mGy,B组CTDIvol为(9.13±2.11)mGy,C组CTDIvol为(6.64±0.94)mGy,三组数据显示各组受检者所接受有效辐射剂量明显不同,且组间两两比较差异有统计学意义。B组较A组(CTDIvol)和剂量长度乘积(DLP)分别减少了35.11%和34.23%,C组减少的更多,分别为52.81%和56.08%。
(2)在对图像质量的主观评分中,两名医师对A组、B50组和C70组的评价结果显示均能满足临床诊断需求,两名医师对三组图像评价的一致性中等(平均Kappa值为0.469)。伴随NI值的增高,放射剂量的减低,A组、B组、C组三组图像质量评分依次下降,其中A组评分最高,C组评分最低(肝实质评分为2.7)。选取不同感兴趣区的评分差异也各不相同,实质脏器的评分结果看,B、C两组较A组得分下降明显,而对小肠肠壁、肠系膜脂肪及肠系膜血管的显示B、C两组得分较A组得分也有所减低,但程度没有肝脏、脾脏等实质脏器减低明显。对经ASIR重建的B50组和C70组的图像质量评分较A组均相差无几。
(3)所有受检者小肠CT造影显示阳性结果共78例,其中感染性疾病最多21例,肿瘤及肿瘤样病变19例,血管瘤及血管性病变9例,淋巴瘤7例,肠道憩室5例,另结肠占位7例,肝腺瘤1例,轻度肠梗阻3例,直肠癌2例,降结肠淋巴瘤、腹膜腔内恶性间叶组织肿瘤、结肠癌伴肝实质多发转移、腹腔内多发小间质瘤各1例。
结论：
(1) HDCT可以在获得稳定图像质量的同时,大幅度降低扫描辐射剂量。
(2) ASIR重建技术在低剂量扫描同时,能充分起到降低噪声,抑制伪影,提高图像质量的作用。
(3)不同ASIR重建值对图像的噪声水平改变不同。
Background and Purpose:
Samall intestine is the longest part of the digestine tract, and its accounted about 75% of the total length of the gastrointestinal tract,and its Starting at the antrum secluded entrance, issued the ileum distal to the ileocecal junction.the most important places for human food digestion and nutrient absorption of various digestive juices in the small intestine in chymedecomposition, afterdigestion and absorption of residues excreted. Small intestinal disease is very common, some were intestinal primary disease, and some were secondary disease. Once the small intestine diseases, It can cause digestion and absorption barriers, some of the primary disease can even cause other systems of the body a series of related symptoms. With the improvement of living standards of the people and the way people work, life style and dietary changes in the structure, gastrointestinal diseases showed a rising trend, the small intestine disease incidence is also increasing. But the lengthy small intestine and mutual folding of the physiological and anatomical characteristics, the cause of small bowel diseases diagnosis method is relatively scarce, and in the diagnostic of imaging, the inspection of small bowel diseases has been a blind spot. There are several common intestinal diagnostic methods such as oral barium small bowel imaging,small bowel barium double contrast small bowel magnetic resonance imaging, MRI and multislice spiral CT enterography imaging methods, In recent years, the clinical use other methods, such as double balloon enteroscopy and small bowel capsuleits own advantages and disadvantages of endoscopy, a variety of inspection methods. The main subject of multislice spiral CT enterography imaging method is to diagnose the small bowel disease, in order to observe its effect. Conventional small bowel contrast need to do the whole abdomen scan, so the effective radiation dose for each position up to 11.7 mSv, (single serial scan), On the other hand in order to increase the sensitivity and specificity of the lesions showed increase in the detection of positive lesions rate, small intestine CT angiography is often necessary for dual-phase or three scanning of the whole abdomen (unenhanced added enhancements), which will undoubtedly further increase the scanning radiation dose. And the dose of ionizing radiation in recent years has more and more attentionned for human. So my topic select whom body mass index in less than normal, and clinical suspicion of intestinal diseases and some people do healthy subjects, expand the small intestine contrast study with Gem CT low-dose scanning, combined with the latest iteration of the Adaptive Statistical Iterative Reconstruction technology (ASIR) technology designed to explore the clinical value of small bowel disease with the low dose scanning.
Materials and methods:
(1)General Information
Select 120 patients(male71 49 female, age 16-78 years old, average 39.7 years) from April 2010 to March 2011 in our hospital or outpatient who visits in patients and suspected has small bowel disease and randomly divided them into three groups (A, B, and C), And all of them made full abdominal CT scanning, The average age of group A patients (40.8±15.4Y), group B patients with average age (37.6±14.1 Y), group C patients with average age (36.9±16.8Y)). Group A conventional-dose scan, B and C the two groups for the experimental group, respectively, take low-dose scan. All patients included in this subject body mass index (body mass index, BMI= body mass/height 2)<25Kg/m2. All patients had no intravenous bolus injection of contrast agent to enhance scans contraindications, and accept the HDCT small bowel imaging, to complete the entire scanning process.
(2) Prepare in advance
Two days before the test, all patients with small bowel imaging needs of low-fat, low fiber, liquid diet, check the first 8-12 hours of oral laxatives, fasting before the test meal. Ask the patient a history of allergies, Patients who have a history of glaucoma, prostatic hypertrophy, embolism, and dysuria were banned intramuscular injection of hydrochloric acid 654-2 injection, the patient if the symptoms of acute intestinal obstruction can not oral contrast to those who do not do this check.
(3) Equipment and scanning methods
With GE gem CT (Discovery 750HD) models, scan range from the top of diaphragm to the pubic symphysis. Scanning technical parameters fixed noise index, a fixed tube voltage 120KVP, automatic mA range (100-600mA), pitch 1.375:1, collimator width of 128 X 0.625mm. Different groups of noise (noise index, NI) settings are as follows:A, B, C noise NI by default 9,12,14; in group A with conventional-dose scan, group B and group C with low-dose scan, on the basis of the original scan data, respectively, an image of the group B patients with 50% ASIR reconstruction image of the group C patients with 70% ASIR reconstruction, respectively, two different sets of images, denoted B50 is C70, reconstruction slice thickness 5mm, interval of 5mm.
The sweep of the scanning sequence level plus dual-phase enhanced scan, the cubital vein injection of nonionic contrast agent to 3.5 ml/s,100ml/bottle, dose 1.5ml/kg. After injection, aortic CT value 200HU automatically trigger the arterial phase scan (diagnostic delay time 5s), generally 25s～30s; 40s vein phase scans in the arterial phase on the basis of delay, usually 65～70s. Retrospective image slice thickness 0.625mm, ADW4.4 workstation deal with reconstruction after the necessary number of, for example, multi-planar reconstruction (Multi Planar's Reformation MPR), maximum intensity projection (Maximum of Intensity Projection is the MIP) and volume rendering (Volume Rendering, VR), in order to meet the diagnostic needs.
(4) Image quality
Subjective evaluation:Each set of images includding the reconstructed image transmitted to the PACS, shielding every patients all scan parameters and related information. Respectively choose the same level reconstruction sequence to compare the image quality for the same patient, Select the approximate level of comparison for different patients, For example,the liver parenchyma select the second hepatic hilum, small intestine and intestinal fat image monitoring select the waist 1 vertebral level. A fixed standard abdominal window width and window level. Be judged on image quality by 2 independent senior radiologists for disease diagnosis, differences of opinion, through consultation, to reach agreement. Quantitative evaluation of image quality based on the anatomical structure, the observation of abdominal parenchymal organs (liver), the small intestinal mucosa, small intestine showed the structural clarity and noise of the intestinal weeks fat and mesenteric vessels. On image quality with a 5-point rating:unqualified, can not meet the diagnostic requirements for 1 minute; less able to meet the diagnosis of the basic requirements, but can not satisfy the differential diagnosis of the need for 2 minutes; in general, to meet the diagnostic requirements for 3 minutes; good to meet the diagnostic requirements for 4 minutes; outstanding, to meet the diagnostic requirements for 5 minutes. Quantitative score of≥3 points was considered the image quality to meet the clinical needs.
Objective evaluation:measurement of each group of the liver, spleen substance and mesenteric fat regions of interest (of VOI:100mm2) CT value and its standard deviation, standard deviation instead of the objective image noise (SD), and calculate the signal-to-noise ratio (SNR), contrast letter noise ratio (CNR). Appropriate statistical analysis of the obtained data.
(5) The radiation dose:
Recorded three groups of patients received radiation parameters:volumetric CT dose index (CT dose index voulme, CTDIvol), dose-length product (a dose length product, DLP) is generated by the machine automatically calculate and estimate the effective dose (Effective Dose, the, ED), the formula ED=DLPX0.015.
(6) Statistical methods:
Use SPSS 17.0 statistical software, measurement data are expressed(x±s).The difference between the groups A, B, B50, C, C70 set of CT values, the noise (SD) signal-to-noise ratio (SNR), contrast to noise ratio (CNR) using single-factor analysis of variance or Kruskal-Wallis rank sum test, The measure between the number of pairwise comparisons of LSD-t test or Bonferonni correction test; The B、C and B50. C70 between the two sets of the original image, noise (SD the differences between groups comparison), the signal-to-noise ratio (SNR), contrast to noise ratio (CNR) using independent samples t test; About A、B、C three groups of age, body mass index (BMI), CT dose index (CTDIvol) dose length product (DLP), the effective dose (ED) measurement data indicators of differences in the single factor analysis of variance; Two physicians using a five-point scale to assess the image quality and consistency in the evaluation of interobserver Kappa test,≥0.75 on behalf of consistent good,0.4-0.75 on behalf of the consistency,and<0.75 is less consistently.
Results:
(1) three groups of patients, the average height, body mass index were no significant differences (P> 0.05). Contrast between the three groups of the original image excellent score group differences, pairwise comparisons of group A and group B, group A and group C, group B and group C there were significant differences. No significant pairwise differences between the two sets of images in group A and re-B50, C70 group, and the score results can meet the diagnostic needs. Contrast to noise (SD) between the signal-to-noise ratio (SNR), contrast to noise ratio (CNR) contrast were different between groups, pairwise comparisons of group A and group B, group A and group C, group B and the difference between group C were statistically significant, but no significant pairwise differences between group A, B50 and C70 group group. The image data group C noise, group A SNR and CNR values. Group A CTDIvol (14.07±2.19) of mGy, CTDIvol Group B (9.13±2.11) of mGy, CTDIvol group C (6.64±0.94) of mGy between the two groups statistically significant pairwise differences. Group B compared with group A (CTDIvol) and dose length product (DLP) were reduced by 35.11% and 34.23%, Group C reduced more for 52.81% and 56.08%, respectively.
(2) the subjective rating of image quality, the two physicians'evaluation of group A, B50, and C70 group results can meet the clinical diagnostic needs, two physicians three sets of image evaluation of the consistency of medium (average Kappa value of 0.469). Accompanying NI values increased, the reduction of radiation dose, group A, group B, group C, three sets of image quality score, followed by decline in group A, the highest scores, group C the lowest score (liver parenchyma score of 2.7). Select a different region of interest of the differences in scores of the same score in the substance of the liver, spleen and other organs results of B, and C group compared with group A score significantly decreased, while the small intestine, the intestinal wall, mesenteric fat and mesenteric vessels display B, C, two sets of score compared with group A score has also been reduced, but the degree does not reduce significantly the substance of the liver, spleen and other organs. Image quality rating by the the ASIR renewal B50 group and the C70 group compared with group A are almost the same.
(3) the small intestine of all subjects with CT angiography showed positive results of 78 cases, of which up to 21 cases of infectious diseases, tumors and tumor-like lesions of 19 cases,9 cases of vascular tumors and vascular lesions,7 cases of lymphoma, intestinal diverticula 5 cases of colon placeholder eight cases, liver adenoma, intestinal obstruction in three cases, two cases of rectal cancer, descending colon, lymphoma, colon cancer with liver parenchyma multiple transfer one cases, multiple intra-abdominal small stromal tumors one cases.
Conclusion:
(1) HDCT can in a stable image quality at the same time, greatly reduce scanning radiation dose.
(2) ASIR Adaptive Statistical Iterative Reconstruction technology can reduce the noise rise adequately, restrain the artifact, improve the quality of image when the low doses scanning were taken.
(3) Different ASIR reconstruction make the different value of the noise level for the image change.
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[16]Friedman S (2004) Comparison of capsule endoscopy to other modalities in small bowel [J]. Gastrointest Endoscopy Clin of N Am; 14:51-60
[17]范辉堂,熊国平.辐射量及其单位的含意和概念[J].公共卫生与预防医学,2006,17(6)：111-112
[18]洪惠民,张忠.CT扫描受检者辐射剂量与防控研究[J].中华预防医学杂 志.2010,16,(4)：19-22
[19]余晓锷,冯晓刚,林意静,等.CT设备的测量与分析[J].中华放射医学与防护杂志,2000,20(4)：286.
[20]葛丽娟,赵兰才,侯长松,等.螺旋CT机辐射剂量的评价[J].中华放射医学与防护杂志,2003,23(2)：108-109.
[21]张朝利,耿振林,费军,等.多层螺旋CT低mAs扫描技术在胸部的应用[J].中华放射医学与防护杂志,2004,24(1)：74.
[22]王巍,张经建.儿童CT曝光参数优化设置控讨[J].中华放射医学与防护杂志,2003,23(4)：292-293.
[23]Wildeberg JE, Mahnken AH, S chmitsrode T, et al.Individually adopted examination protocols for reduction of radiation exposure in chest CT[J].Invest Radiol,2001,36:604-611.
[24]Suess C, Chen X. Dose optimization in pediatric CT:current technologyand Future in novations[J].Pediatr Radiol,2002,32:729-734.
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[1]钟捷,张晨莉,金承荣,等.双气囊小肠镜在诊断小肠克罗恩病中的价值[J]中华消化内镜杂志,2006,23(2)：86-89.
[2]张子其,陈孝,张建平,等.胶囊内镜对小肠疾病的诊断价值分析[J].中华消化内镜杂志,2003,20：226-229.
[3]SunB, RajanE, Cheng S, et al.Diagnostic yield and therapeutic impact of double. balloon enteroscopy in a large cohort of patients with obscure gast rointestinal bleeding[J].Gast roenterol,2006,101:2011-2015.
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[15]胡志海,姜荣.适应性统计迭代重建技术胸部低剂量CT图像噪声的效果[J].中国医学影像技术.2011,27(12)：2398-2402
[16]FujiiK,AoyamaT,KoyamaS etal(2010)Comparative evaluation of organ and effective doses for paediatric patients with those for adults in chest and abdominal Ctexaminations[J].BrJ, Radiol80(956):657-667
[17]张兆琪,徐磊.重视冠状动脉多层CT成像的低剂量检查[J].中华放射学杂志,2009,43(7)：681-683.
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[2]程英升,宋富珍.小肠疾病影像学诊断新进展[J].世界华人消化杂志,2007,3(8)；15(7)：669-676
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[11]徐志荣,徐汀,王振洲,等.CT能谱成像新技术及应用[J].中国医学装备.2011,8(1),25-26
[12]安瑞金,黄岗.CT图像质量和辐射剂量的影响因素研究[J].生物医学工程与临床.2009,12(2),92-95.
[13]CynthiaH, McCollough, PhD, (2009)Strategies for Reducing Radiation Dose in CT[J].Radiol Clin North Am.January;47(1):27-40.
[14]胡志海,姜荣.适应性统计迭代重建技术胸部低剂量CT图像噪声的效果[J].中国医学影像技术.2011,27(12)：2398-2402
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[17]范辉堂,熊国平.辐射量及其单位的含意和概念[J].公共卫生与预防医学,2006,17(6)：111-112
[18]洪惠民,张忠.CT扫描受检者辐射剂量与防控研究[J].中华预防医学杂 志.2010,16,(4)：19-22
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[22]王巍,张经建.儿童CT曝光参数优化设置控讨[J].中华放射医学与防护杂志,2003,23(4)：292-293.
[23]Wildeberg JE, Mahnken AH, S chmitsrode T, et al.Individually adopted examination protocols for reduction of radiation exposure in chest CT[J].Invest Radiol,2001,36:604-611.
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[26]赵锡海,许建荣,华佳,等.联合应用口服水剂和水灌肠肠道充盈法的MSCT研究[J].中国医学影像杂志,2006,14(6)：409-412.
[27]章士正,任小军.应用现代医学影像技术提高小肠疾病诊断水平[J].中华医学杂志,2005,85(5)：301-302
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[29]张联合,章士正,胡红杰.口服甘露醇多层螺旋CT小肠造影的临床价值[J].中华放射学杂志,2005,39(4)：423-427
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[1]钟捷,张晨莉,金承荣,等.双气囊小肠镜在诊断小肠克罗恩病中的价值[J]中华消化内镜杂志,2006,23(2)：86-89.
[2]张子其,陈孝,张建平,等.胶囊内镜对小肠疾病的诊断价值分析[J].中华消化内镜杂志,2003,20：226-229.
[3]SunB, RajanE, Cheng S, et al.Diagnostic yield and therapeutic impact of double. balloon enteroscopy in a large cohort of patients with obscure gast rointestinal bleeding[J].Gast roenterol,2006,101:2011-2015.
[4]DelabrouseE, Dest rumelleN, BrunellS, et al. CT of small bowel obstruction in adult s[J].Abdeom Imaging,2003,28:257-266.
[5]ICRP. Recommen dation of the International Commission Radiological Protection: Publication 60[M],1990:11-13.
[6]FergusV. Coakley, Robert Gould Benjamin M.YehRonald L.Arenson.CT Radiation Dose: What Can You Do Right Now in Your Practice? [J].AJR:196,March 2011
[7]BrennerDJ, Hall EJ.Computed tomography-an increasing source of radiation xposure[J]. N EngMed,2007; 357:2277-84.
[8]TubianaM, AurengoA, AverbeckD, MasseR. The debate on the use of linear on threshhold for assessing the effects of low doses [J].Radiol Prot,2006; 26:317-24.
[9]LePogam MA, RubinoC, DialloI, et al.Radiation dose fractionation and second cancer risks after breast cancer treatment.Radiat Prot Dosimetry (in press).
[10]Jensch S, van Gelder RE, Venema HW, et al.Effective radiation doses in CT colonography: results of an inventory among research institutions[J].Eu, Radiol,2006;16:981-987
[11]IMV Medical Information Division, Inc. IMV2006 CT market summary report. www.imvinfo.com/user/documents/content_documents/nws_rad/MS_CT_DSandTOC.pdf. Published 2006. Accessed September16,2009.
[12]徐志荣,徐汀,王振洲,等.CT能谱成像新技术及应用[J].中国医学装备.2011,8(1),25-26
[13]王健.宝石CT的技术突破和临床应用[J].国际放射医学核医学杂志,2009,33(2)：126-128.
[14]林晓珠,李卫侠,吕培杰,等.宝石能谱CT在肿瘤诊断中的初步应用[J].诊断学理论与实践,2010,9：155-160
[15]胡志海,姜荣.适应性统计迭代重建技术胸部低剂量CT图像噪声的效果[J].中国医学影像技术.2011,27(12)：2398-2402
[16]FujiiK,AoyamaT,KoyamaS etal(2010)Comparative evaluation of organ and effective doses for paediatric patients with those for adults in chest and abdominal Ctexaminations[J].BrJ, Radiol80(956):657-667
[17]张兆琪,徐磊.重视冠状动脉多层CT成像的低剂量检查[J].中华放射学杂志,2009,43(7)：681-683.
[18]秦新裕.小肠肿瘤的诊治现状及发展趋势[J].中国实用外科杂志,2008,28(11)：929-930.
[19]任小军,章士正,刘海,等.X线、CT和MRI对小肠Crohn病诊断价值的评价[J].中国医学计算机成像杂志,2005,11(3)：184-189.
[20]章士正.小肠影像诊断学[M].第一版.北京人民军医出版社.2006：7
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