【作者】 杨世锋；

【导师】 武乐斌； 王锡明；

【作者基本信息】 山东大学 ， 影像医学与核医学， 2014， 博士

【摘要】 第一部分低剂量回顾性心电门控全主动脉CTA的可行性及其显示夹层解剖细节的价值目的：探讨急性主动脉夹层(aortic dissection, AD)低剂量回顾性心电门控全主动脉CTA的可行性及其对显示内膜片破口、主动脉分支血管起源和判断真腔塌陷的价值。材料方法：本研究前瞻性纳入2012年1月至2012年11月怀疑或确诊为AD患者49例。其中男33例,女16例,平均年龄49.25±10.4岁。所有患者均采用西门子第二代双源CT机进行低剂量回顾性全主动脉心电门控CTA检查。AD患者每隔5%心动周期进行图像重建,共重建0%、5%、10%……95%等20个心动周期的图像。测量70%心动周期图像升主动脉、胸主动脉(肺动脉分叉水平)及腹主动脉远段(髂总动脉分叉上2cm)真腔的CT值、噪声并计算信噪比(signal noise ratio,SNR)。两名经验丰富的放射科医师独立阅片,对70%心动周期主动脉图像进行主观图像质量评分。评分标准如下：3分,图像质量好,无运动或阶梯状伪影；2分,图像质量尚可,稍有模糊但仍可评价；1分,图像质量差,图像明显模糊或解剖结构边缘出现重影,无法评价。比较单期图像(70%心动周期)和多期图像(0%～95%心动周期)对AD内膜片的破口及主动脉主要分支起源的诊断信心。评分标准如下：3分,确信；2分,适度确信；1分：无法判断。两名医师共同评价升主动脉、胸主动脉(右肺动脉干水平)及腹主动脉(腹腔干开口上2cm)横轴位图像内膜片,判断各心动周期不同部位内膜片有无运动伪影,分析运动伪影与心动周期的关系。两名医师共同判断腹主动脉真腔有无塌陷,并根据塌陷的特征(完全性塌陷和部分性塌陷),分析真腔塌陷类型与腹主动脉分支器官动态缺血的关系。记录患者容积CT剂量指数(volume CT dose index, CTDIvol)和剂量长度乘积(dose length product, DLP),并计算有效辐射剂量(Effective Dose, ED)。采用SPSS17.0(SPSS, Chicago, IL, USA)统计学处理软件对数据进行分析。Cohen’S k-test比较2名放射科医师对主观图像质量评价的一致性(k=0.21～0.4为一致性差,k=0.41-0.6为一致性中等,k=0.61-0.8为一致性良,k=0.81-1.0为一致性优)；配对t检验比较同一患者升主动脉及主动脉远段血管强化程度的差异性。采用两独立样本秩和检验,比较两组图像对内膜片破口及主动脉分支起源诊断信心的差异性。P<0.05表示差异有统计学意义。结果：升主动脉、胸主动脉及腹主动脉远段真腔的CT值分别为386.9±63.6HU,381.4±55.3HU和377.6±60.0HU；升主动脉、胸主动脉及腹主动脉远段噪声分别为26.8±6.4.23.2±5.5和24.4±5.1。相应的SNR分别为14.7±2.9,16.8±2.3和15.3±2.7。升主动脉及腹主动脉远段真腔强化程度无明显统计学差异(P>0.05)。两位放射科医师对主观图像质量评价的一致性为优秀(k=0.83)。2名放射科医师对主动脉瓣、升主动脉壁、降主动脉壁及左、右冠状动脉起始部主观图像质量评分分别为2.83±0.42、2.88±0.33、2.94±0.24、2.88±0.33和2.92±0.27。89.8%图像评分为3级。仅1例主动脉瓣由于主动脉根部扩张且伪影明显评分为1级。两组图像对于升主动脉内膜片破口显示的诊断信心多期相组明显优于单期像组(P<0.05)。而两者对于主动脉弓-降主动脉移行区、腹主动脉内膜片破口显示及主动脉分支起源诊断信心无统计学差异(P>0.05)。25.7%升主动脉内膜片可见运动伪影。17.9%胸主动脉内膜片可见运动伪影。13.4%腹主动脉内膜片可见运动伪影,72%有运动伪影的内膜片位于心动周期0%-40%。13例患者(158期图像)可见真腔塌陷。其中4例为真腔完全塌陷,其余9例为真腔部分塌陷。共4例患者7支腹主动脉血管供血器官诊断为动态缺血,其受累分支血管开口处真腔均为完全性塌陷。患者的平均CTDIvol为16.1±6.8(7.6～33.6)mGy,平均DLP为896.4±373.4(450.1～1850.1)mGy.cm,平均ED为12.7±5.3(6.4～26.3)mSv。结论：低剂量回顾性心电门控全主动脉CTA是可行的。对于AD患者,多期相图像较单期图像具有更高的识别夹层解剖细节的能力,并能准确判断真腔有无塌陷及其塌陷程度,具有直接和早期诊断腹主动脉分支动态阻塞的潜力,可为临床了解病情及制定治疗方案提供更多信息。第二部分低剂量回顾性心电门控全主动脉CTA评估腹主动脉内膜片运动：可行性及内膜片运动规律研究目的：评估急性主动脉夹层(aortic dissection, AD)患者低剂量回顾性心电门控全主动脉CTA评价腹主动脉内膜片搏动的可行性及探讨腹主动脉内膜片运动规律。材料与方法：回顾性纳入2012年1月至2012年11月于本院行低剂量回顾性心电门控全主动脉CTA检查且腹主动脉有双腔显示的急性AD患者31例。其中男22例,女9例,平均年龄50.35±9.6岁。所有患者均采用西门子第二代双源CT机进行扫描。每隔5%心动周期进行图像重建,共重建0%、5%、10%……95%等20个心动周期的图像。两名放射科医师独立测量腹腔干开口上2cm处的真腔最短直径(true lumen short axis diameter, TLD)及假腔最短直径(false lumen short axis diameter, FLD)。将内膜片形态分为曲向真腔、曲向假腔和平直三种。两名观测者独立评价内膜片形态,当两者意见不一致时,两者进行共同阅片,直至意见一致为止。用心动周期的百分比确定心动周期的期相以利于不同病人间的比较。内膜片的运动幅度通过5%心动周期内的真腔直径的变化来量化。它表达为相邻真腔直径差值的绝对值(absolute value of relative change between the TLD, RCTLD)。在真腔直径测量的基础上,计算以下参数：(1)一个心动周期内最大真腔直径(maximum TLD, TLDmax)与最小真腔直径(minimum TLD, TLDmin);(2)一个心动周期内真腔直径运动范围(the maximum change of TLD, MCTLD)和最大真腔直径相对变化(relative decrease of TLD, RDTLD):真腔直径运动范围是一个心动周期内TLDmax与TLDmin的差,它反映了内膜片在一个心动周期内运动的范围；真腔最大直径相对变化是MCTLD与TLDmax的比,它反映了真腔最大直径在一个心动周期内缩小的程度。(3)5%心动周期内的内膜片运动幅度和真腔最大运动期相(maximum motion phase, MMP):5%心动周期内的内膜片运动幅度即为RCTLD,反映了真腔直径在5%心动周期内的变化。MMP是指最大的RCTLD所在的期相。计算公式如下：MCTLD=TLDmax-TLDmin;RDTLD=(MCTLD/TLDmax)×100%RCTLDn=|TLDn-TLD(n-1)|“n”表示心动周期的某一期相,“(n+1)”表示相邻的后面的期相。Bland-Altman分析法评价两名观测者对真、假腔最短直径测量的一致性。Kappa检验评价2名放射科医师对内膜片形状分类的一致性(k>0.81认为一致性优,k=0.61-0.8为一致性良,k=0.41-0.6为一致性中等)。采用Bonferroni post-hoc方差分析方法比较不同心动周期的FLD、TLD和RCTLD的统计学差异。P<0.05为差异有统计学意义。所有统计均采用SPSS17.0(SPSS, Chicago, IL, USA)统计学处理软件处理。结果：AD发病时间为2小时至12天。参考DeBakey分型,20(64.5%)例为I型AD,11(35.5%)例为III型AD。Bland-Altman检验显示不同观测者测量真、假腔最短直径具有良好的一致性。二者测得的真腔直径及假腔直径偏移分别为0.085和0.078,95%可信区间分别为1.63～-1.46和1.41～-1.25m。不同观测者在内膜片形状分类上具有很好的一致性(k=0.93)。在15%心动周期,所有患者平均真腔直径最小(8.67±5.16mm)而平均假腔直径最最大(19.44±4.07mm),但与其它期相比较,两者均无统计学意义(P>0.05)。TLDmax、TLDmin、MCTLD和RDTLD分别为12.2±4.1m(2.6～17.4)、6.7±4.1mm(0～15.3)、5.5±2.6mm(1.8～10.2)并49.5%±23.5%(12%～100%)。MMP均位于收缩期及舒张早期(心动周期5%-40%)。平均RCTLD与心脏搏动同步,其峰值(1.82±1.69mm)位于15%心动周期。在本期相上,内膜片运动幅度均高于其它期相(0%-10%,55%-95%：p<0.05；20%-50%：p>0.05)。内膜片平均运动幅度最小的期相位于心动周期的75%,内膜片平均运动幅度次小的期相位于心动周期的70%。在这两个心动周期上,内膜片搏动幅度均小于其它期相(15%,20%:p<0.05; O%～10%,25%～95%: p>0.05)。312(50.3%)例内膜片曲向假腔,226例(36.5%)曲向真腔,82(13.2%)例内膜片呈平直状,三种内膜片形状在各期相均可见。50.3%(312例)的内膜片曲向假腔,大部分(85.6%)曲向假腔的内膜片位于心动周期的0%-5%和35%-95%%。36.5%内膜片(226例)曲向真腔,曲向真腔的内膜片多位于10-30%心动周期内。82(13.2%)例内膜片呈平直状。83(13.4%)例腹主动脉内膜片可见运动伪影。运动伪影最常见于收缩期及舒张早期。31例病人的CTDIvol、DLP、和有有效辐射剂量分别为16.9±7.4(9.6-33.6)mGy,936.4±353.1(540.3～1850.1)mGy.cm,和13.4±6.1(7.4-26.3)mSv。结论：低剂量回顾性心电门控全主动脉CTA可以评估腹主动脉内膜片运动。腹主动脉内膜片是一个动态结构,其运动幅度在收缩中、晚期最明显。内膜片位置和形状在心动周期不同期相上变化很大,心电门控CTA扫描所得单期相图像或非心电门控扫描所得图像不能准确反映真腔的真实状态,回顾性心电门控CTA多期相图像分析能够反映真腔的真实状态,提供更多关于真腔塌陷的信息,这些信息可能对诊断和鉴别诊断动态缺血具有帮助。更多还原

【Abstract】 Part I:Low dose retrospective ECG-gated thoracoabdominal aorta CTA in patients with acute aortic dissection:feasibility and additional diagnostic valueObjectives:To assess feasibility and additional diagnostic value of low dose ECG-gated thoracoabdominal aorta CT angiography (CTA) in patients with acute aortic dissection (AD).Materials and methods:From January2012to November2012, a total of49consecutive patients were prospective enrolled in the study. The ages were ranged from30to73years old (mean age,49.25±10.4years), and there were33men and16women. Low dose ECG-gated thoracoabdominal aorta CTA was performed by dual-source CT (DSCT). Functional imaging was reconstructed in5%steps between0and95%of the R-R interval from the ECG with1-mm slice thickness,0.8-mm increments, I26f reconstruction kernel and24cm FOV in patients with acute AD. Aortic intraluminal attenuation, image noise and signal noise ratio(SNR)were assessed as objective image quality parameters at datasets acquired with full tube current (70%R-R interval). The ROIs were placed in the ascending aorta, descending aorta at the level of the right pulmonary trunk plane and at the level of2cm above the celiac trunk ostium. Blinded image interpretation of70%R-R interval image was performed on a3D workstation by two experienced vascular radiologists. Subjective image quality was categorized into three groups:grade3(no artifacts, all anatomical details assessable); grade2(mild artifacts, majority of the anatomical structures assessable); grade1(severe artifacts, no anatomical structures assessable). Diagnostic confidence of intimal flap rapture and origin of aorta brunches were determined for both the mono-phases (70%R-R interval) and multi-phases (0%-95%R-R interval). Diagnostic confidence was rated on a3-point scale (1=uncertain,2=moderately confident,3=fully confident). Motion artifact of intimal flap of each phase was assessed at ascending aorta, thoracic aorta (at the level of the right pulmonary trunk plane) and abdominal aorta (at the level of2cm above the celiac trunk ostium) by a consensus reading of two radiologists. The frequency distributions of intimal flap motion artifacts during a cardiac cycle were analyzed. True lumen collapse was sorted as complete collapse (true lumen collapsed at every R-R intervals at the same level) and partial collapse (true lumen collapsed at one or more R-R intervals at the same level).The relationship of true lumen collapse and dynamic obstruction were analyzed. The volume CT dose index (CTDIvol) and dose length product (DLP) were provided by the scanner. The effective dose (ED) was determined by using DLP and appropriate normalized coefficients k (k=0.0142mSv.mGy-1.cm-1). All statistical analyses were performed with statistical software SPSS17.0The intra-observer agreement in image quality grading was evaluated by kappa test, and K-values of0.41-0.6corresponded to moderate agreement, K-values of0.61-0.80corresponded to good agreement, and0.81-1.00corresponded to perfect agreement. The intraluminal attenuation difference of ascending aorta and abdominal aorta were compared with the paired two-tailed Student’s t-test. The grades of two datasets diagnostic confidence were compared using Wilcoxon rank sum test. A value of p<0.05was considered statistically significant.Results:Aortic intraluminal attenuation of ascending aorta, descending aorta and abdomen aorta were386.9±63.6HU,381.4±55.3HU and377.6±60.0HU respectively. Image noise of ascending aorta, descending aorta and abdomen aorta were26.8±6.4,23.2±5.5and24.4±5.1respectively. SNR of ascending aorta, descending aorta and abdomen aorta were14.7±2.9,16.8±2.3and15.3±2.7respectively. There were no statistically significant differences in intraluminal contrast attenuation between ascending aorta and abdomen aorta (p>0.05).The inter-observer agreement for subjective image quality was excellent (k=0.83).Assessment of ascending aorta wall, descending aorta wall,aortic valve and the origin of the coronary arteries subjective image quality were2.83±0.42、3±0、2.94±0.24、2.88±0.33和2.92±0.27.89.8%structures of aorta were depicted with no motion artifacts. Only1aortic valve (2.0%) was depicted severe artifacts. The diagnostic confidence in multi-phases images was statistically higher compared to that in mono-phase images at ascending aorta intimal flap rapture(P<0.05), but not at the descending aorta and abdominal aorta flap rapture (P>0.05).The diagnostic confidence in multi-phases images was no statistical differences compared to that in mono-phase images at the origin of aorta brunches(P>0.05).128of460(25.7%) intimal flaps had motion artifacts at ascending aorta.122of680(17.9%) intimal flaps had motion artifacts at thoracic aorta.83of620(13.4%) intimal flaps had motion artifacts at abdomen aorta.72%intimal flaps with motion artifacts were at0%～40%of R-R interval. True lumen collapse was found in13of31cases.4cases were complete collapse and9cases were partial collapse.7visceral vessels (3superior mesenteric arteries,2celiac trunks and2renal arteries) in4patients were diagnosed with typical dynamic obstruction. True lumens were completely collapsed at the level of the involved branch origins in these4cases. The CTDIvol, DLP, and ED were16.1±6.8(7.6-33.6) mGy,896.4±373.4(450.1～1850.1) mGy.cm, and12.7±5.3(6.4～26.3) mSv respectively.Conclusions:We have demonstrated the feasibility of low dose retrospective ECG-gated CTA covering the entire aorta while keeping the radiation dose in standard limits. In patients with acute AD, low dose retrospective ECG-gated CTA multi-phases images can provide more substantial diagnostic information with potential therapeutic consequences than mono-phases images. Retrospective ECG-gated thoracoabdominal aorta CTA multi-phases images can reflect the actual status of the true lumen and provide more information about true lumen collapse. This information may be helpful to diagnosis and differential diagnosis of dynamic abstraction. Part II Low dose retrospective ECG-gated thoracoabdominal aorta CTA evaluating abdomen aortic intimal flap motion in patients with acute aortic dissection:feasibility and intimal flap motion characterizationObjectives:To evaluate the feasibility of low dose retrospective ECG-gated thoracoabdominal aorta CT angiography (CTA) assessing abdominal aortic intimal flap motion and investigate the motion characteristics of intimal flap in acute aortic dissection (AD).Materials and methods:From January2012to November2012, a total of31consecutive patients (22men,9women; age range,30-72years, mean age±standard deviation,50.35±9.6years) were retrospective enrolled in the study. Low dose ECG-gated thoracoabdominal aorta CTA was performed by dual-source CT (DSCT). Imaging was reconstructed in5%steps between0and95%of the R-R interval from the ECG with1-mm slice thickness,0.8-mm increments, I26f reconstruction kernel and24cm FOV in patients with acute AD. The true lumen short axis diameter (TLD) and the false lumen short axis diameter (FLD) were measured at the level of2cm above the celiac trunk ostium at different phases of a cardiac cycle by two independent observers. The configuration of the intimal flap was classified as curved toward the false lumen, curved toward the true lumen and flat. It was assessed independently by the two observers. In case of disagreement in classifying between the observers, a final decision was obtained by consensus.All time instances were expressed as percentages of the R-R interval to enable comparisons of intimal flap motion amplitude for all patients. The motion amplitude of intimal flap was quantified by the change of the TLD at every5%R-R interval. It was expressed as the absolute value of relative change between the TLD (RCTLD) of adjacent phases of R-R interval. On the basis of measurements, the following variables were obtained:(1) Maximum true lumen diameter (TLDmax) and minimum true lumen diameter (TLDmin) during a cardiac cycling.(2)The maximum change of TLD (MCTLD) and relative decrease of TLD (RDTLD) during a cardiac cycle:MCTLD was defined as the difference between TLDmax and TLDmin; RDTLD was defined as the ratios of MCTLD to TLDmax. MCTLD reflect the range of intimal flap motion and RDTLD reflect the extent of TLDmax decreased during a cardiac cycle.(3) RCTLD and maximum motion phase (MMP) of TLD over a cardiac cycle: RCTLD defined as the absolute difference between the TLD of adjacent time intervals, which reflects the change of TLD at a given percentage of time intervals. MMP was defined as the phase of R-R interval where the maximum RCTLD was at. The design formulas were as follow:MCTLD=TLDmax-TLDmin;RDTLD=(MCTLD/TLDmax)×100%RCTLDn=|TLD (n+1)-TLDn|Where "n" represents a given phase of the R-R interval and "(n+1)" represents the next adjacent phase.Interobserver variation of diameter measurement was evaluated by using the Bland-Altman analysis. Interobserver agreement on classifying the intimal flap configuration was calculated before consensus reading by using Kappa statistics. A kappa value of more than0.81corresponded to excellent interobserver agreement, with values of0.61-0.80corresponding to good agreement. Bonferroni post-hoc tests were used for multiple pair wise comparisons of FLD, TLD and RCTLD within time intervals. A value of p<0.05was considered statistically significant. All statistical analyses were performed with statistical software SPSS17.0.Results:Onset time of acute AD was from2hours to12days.20of the31(64.5%) patients were DeBakey I, and11of the31(35.5%) were DeBakey Ⅲ. The Bland-Altman analysis of interobserver variation of diameter measurements demonstrated good results. The measurement error of TLD and FLD were0.085and0.078respectively, whereas the95%limits of agreement werel.630to-1.460and1.410to-1.254mm respectively. Overall interobserver agreement on intimal flap configuration classifying was excellent (k=0.93). Peak of group-averaged FLD (19.44±4.07mm) and trough of group-averaged TLD (8.67±5.16mm) were found at15%of the R-R interval. There were no significant statistical differences comparing to other R-R intervals (p>0.05). The TLDmax, TLDmin, MCTLD and RDTLD in all patients were12.2±4.1mm (2.6～17.4)、6.7±4.1mm (0～15.3)、5.5±2.6mm (1.8～10.2)和49.5%±23.5%(12%～100%) respectively. All of the MMP were at middle and later systolic phase and early diastolic phase (5%～40%of R-R interval). Group-averaged intimal flap motion was synchronized to the heart pulsation. Peak intimal flap motion amplitude (1.82±1.69mm) was found at15%of the R-R interval; group-averaged intimal flap motion amplitude in this interval was higher than those at any other time intervals (0%-10%and55%-95%:p<0.05;20%-50%:p>0.05). The minimum intimal flap motion amplitude was found at75%(0.440±0.31mm) of the R-R interval, and second minimum (0.464±0.31mm) was found at70%of the R-R interval. Intimal flap motion amplitude in these two R-R intervals was less than that in other R-R intervals (15%,20%:p<0.05;0%-10%and25%-95%:p>0.05).3types of intimal flap configurations were found in every R-R intervals.312of620(50.3%) intimal flaps curved toward the false lumen,226of620(36.5%) intimal flaps curved toward the true lumen, and82of620(13.2%) intimal flaps were flat. The CTDIvol, DLP, and ED were16.9±7.4(9.6～33.6) mGy,936.4±353.1(540.3～1850.1) mGy.cm and13.4±6.1(7.4～26.3) mSv respectively.Conclusions:Low dose retrospective ECG-gated thoracoabdominal aorta CTA can assess the abdominal intimal flap motion in acute AD. Abdominal intimal flap is a dynamic structure, and the highest motion of intimal flap was at systolic phase. The position and configuration of intimal flap varied greatly during a cardiac cycle. None ECG-gated CTA or any one phase images from retrospective ECG-gated CTA cannot reflect the actual status of the true lumen. Retrospective ECG-gated thoracoabdominal aorta CTA can reflect the actual status of the true lumen and provide more information about true lumen collapse.更多还原