Pulmonary embolism: optimization of small pulmonary artery visualization at multi-detector row CT

PURPOSE: To compare the frequency of well-visualized pulmonary arteries according to anatomic level by using different collimation with single- and multi-detector row computed tomography (CT) in patients suspected of having acute pulmonary embolism. MATERIALS AND METHODS: Sixty patients were examined with one of three techniques (20 patients each). Group 1 was examined with single-detector row CT with 3-mm collimation and 1.3-1.6 pitch; groups 2 and 3, with multi-detector row CT with 2.5- and 1.25-mm collimation, respectively. Three thoracic radiologists independently reviewed examination findings to determine if each main, lobar, segmental, and subsegmental artery was well visualized for presence of pulmonary embolism. chi2 tests were performed. For well-visualized vessels, the presence and/or absence of pulmonary embolism was recorded and kappa statistic was determined. RESULTS: Reader 1 scored 95% (114 of 120), 96% (115 of 120), and 99% (119 of 120) of lobar arteries (P >.05); 76% (304 of 400), 86% (346 of 400), and 91% (363 of 400) of segmental arteries (P <.001); and 37% (300 of 800), 56% (448 of 800), and 76% (608 of 800) of subsegmental arteries as well visualized (P <.001) using techniques 1, 2, and 3, respectively. Reader 2 scored 97% (116 of 120), 95% (114 of 120), and 99% (119 of 120) of lobar arteries (P >.05); 77% (308 of 400), 87% (349 of 400), and 93% (371 of 400) of segmental arteries (P <.001); and 39% (310 of 800), 53% (422 of 800), and 78% (621 of 800) of subsegmental arteries (P <.001) as well visualized using techniques 1, 2, and 3, respectively. Reader 3 scored 86% (103 of 120), 82% (98 of 120), and 91% (109 of 120) of lobar arteries (P >.05); 63% (252 of 400), 70% (280 of 400), and 85% (339 of 400) of segmental arteries (P <.001); and 39% (310 of 800), 56% (451 of 800), and 71% (572 of 800) of subsegmental arteries (P <.001) as well visualized using techniques 1, 2, and 3, respectively. Sixteen patients had pulmonary embolism. Interobserver agreement for detection of pulmonary embolism was significantly better for segmental and subsegmental arteries for all readers with technique 3 (segmental, kappa = 0.79-0.80; subsegmental, kappa = 0.71-0.76) than that with technique 1 (segmental, kappa = 0.47-0.75; subsegmental, kappa = 0.28-0.54). CONCLUSION: Multi-detector row CT at 1.25-mm collimation significantly improves visualization of segmental and subsegmental arteries and interobserver agreement in detection of pulmonary embolism.     

CT肺动脉成像诊断肺栓塞的读片者一致性研究

目的:评价CT肺动脉成像(CTPA)诊断肺栓塞(PE)时,不同经验的读片者间和同一读片者内的一致性.方法:55例临床可疑PE患者,作了CTPA检查,6位不同经验的放射科医生独立地分析CTPA图像来评价读片者间的一致性.3位放射科医生3个月后第二次分析CTPA图像来评价读片者内的一致性.PE的表现分为阳性、阴性和难以确定.读片者一致性用百分比及Kappa系数表示.结果:6位读片者判定29～31例(平均29.2例)患者CTPA为PE阳性,1～5例(平均3.0例)患者CTPA为难以确定.6位读片者在48例(87.3%)患者CTPA的诊断上取得一致意见,5位读片者在4例患者(7.3%)的诊断上取得一致意见,4位读片者在2例患者(3.6%)的诊断上取得一致意见,3位读片者在1例患者(1.8%)的诊断上取得一致意见.在诊断PE上,如果以每例患者为观察单位,读片者间的一致性"非常好"(Kappa值为0.91).以每个肺动脉为观察单位,读片者间的一致性"好"(85%,Kappa值为0.74);以肺叶动脉为观察单位,读片者间的一致性"好"(89%,Kappa值为0.78);以肺段动脉为观察单位,读片者间的一致性"中等"(75%,Kappa值为0.59).如果以每例患者为观察单位,同一读片者内的平均一致性"非常好"(96%,Kappa值为0.93).结论:在CTPA上诊断PE时,经验不同的读片者间和同一读片者内的一致性均较好.     

Reliability of selective pulmonary arteriography in the diagnosis of pulmonary embolism

To test the reliability of conventional selective pulmonary arteriography in the diagnosis of pulmonary embolism, three angiographers reviewed the arteriograms of a series of 60 patients retrospectively, independently, and without benefit of additional data. Pulmonary arteriograms had been interpreted as positive for pulmonary embolism in 25 of these patients during their hospitalizations. Angiographers A, B, and C judged the arteriograms of 24, 29, and 25 patients, respectively, as positive for pulmonary embolism. Mean interobserver agreement was 86%. Interobserver agreement was not associated significantly with the quality of the arteriogram or with selective injection of a lobar vs a pulmonary artery, but was associated strongly with the magnitude of thromboembolism. All angiographers agreed that the arteriograms were positive in 18 cases of pulmonary embolism graded as massive, lobar, or segmental, but agreed in only two of 15 cases graded as subsegmental. We conclude that conventional selective pulmonary arteriography is reliable in the detection of embolus in segmental or larger pulmonary arteries. Observer disagreement becomes considerable for embolus limited to subsegmental pulmonary arteries, indicating that emboli of this size are at the resolution limit of the technique.     

16层螺旋CT肺血管造影在肺动脉栓塞诊断中的应用

目的　研究 16层螺旋CT肺血管造影在肺动脉栓塞诊断中的应用价值。方法　使用 16层螺旋CT扫描机 (SiemensSensation 16 )对临床拟诊肺栓塞的 4 9例患者进行前瞻性研究。采用层厚 3mm行胸部增强扫描。利用原始数据行层厚 1mm的轴面及多平面重建 (MPR)。比较层厚 3mm、1mm的轴面图像及MPR图像。结果　CT诊断肺栓塞 4 2例。病变共累及肺动脉 35 2支。对于主肺动脉及肺叶动脉栓塞 ,三种图像检出结果一致。但对于肺段及亚段动脉栓塞 ,层厚 1mm较 3mm显示率高 ,差异有显著意义 (P <0 0 1) ,1mm的MPR较轴面图像显示率高 ,但差异无显著性意义 (P >0 0 5 )。结论　 16层螺旋CT肺血管造影无创、快速、敏感性高 ,应当作为肺栓塞的首选检查方法。     

Reassessment of pulmonary angiography for the diagnosis of pulmonary embolism: relation of interpreter agreement to the order of the involved pulmonary arterial branch

PURPOSE: To reassess the validity of conventional pulmonary angiography in the diagnosis of pulmonary embolism (PE) in main, lobar, segmental, and subsegmental pulmonary arteries. MATERIALS AND METHODS: Data are from examinations of 375 patients with angiographically diagnosed PE who participated in the Prospective Investigation of Pulmonary Embolism Diagnosis. The average co-positivity of readings of the pulmonary angiograms was evaluated in relation to the order of the largest pulmonary artery that showed PE. RESULTS: Among 217 patients whose angiograms showed PE in main or lobar pulmonary arteries, as well as in smaller orders of arteries, there was an average co-positivity of 98% (95% Cl = 96%, 98%). Among 136 patients whose pulmonary angiograms showed PE in segmental or subsegmental pulmonary arteries but not in larger orders of arteries, the average co-positivity was 90% (95% Cl = 85%, 95%). Among 22 patients with PE limited to the subsegmental arteries, the average co-positivity was 66% (95% Cl = 46%, 86%). CONCLUSION: Conventional pulmonary angiography is not precise for the diagnosis of PE limited to subsegmental arteries. To evaluate subsegmental arteries, techniques that improve the visualization of PE in small arteries should be used.     

Diagnosis of pulmonary embolism: comparison of CT angiography and MR angiography in canines

PURPOSE: To compare the sensitivity and specificity of helical computed tomographic angiography (CTA), CTA with multiplanar reconstructions (MPR)/three-dimensional-shaded surface display (3D-SSD), and gadolinium-enhanced magnetic resonance angiography (MRA) for pulmonary embolism (PE) detection. MATERIALS AND METHODS: Gelatin sponge emboli were introduced into the femoral veins of seven dogs and conventional digital subtraction angiography (CA), CTA, and MRA performed. Images from CTA, CTA with MPR/3D-SSD, and MRA were reviewed for the presence of PE in lobar and segmental arteries, and subsegmental zones. Postmortem angiography and CA were the gold standard. RESULTS: There were 50 emboli in the 294 vessels/zones analyzed. The sensitivity of CTA for the two readers was 76% (95% confidence interval [CI]; 64%-88%) and 64% (95% CI; 50%-78%), and for the two MRA readers was 52% (95% CI; 38%-66%) and 48% (95% CI; 34%-62%). CTA was more sensitive than MRA when PE were subdivided by vessel caliber. Specificity was high for CTA and MRA among all readers (98.8%-99.6%). MPR/3D-SSD did not improve results of axial CT. MRA perfusion defects were 46% and 47% sensitive and 100% specific. Interobserver agreement was high for CTA and MRA (kappa 0.92 and 0.93, respectively). The average diameter of vessels with emboli was 3.7 mm +/- 1.06. CONCLUSION: Helical CTA is more sensitive than three-dimensional gadolinium-enhanced MRA for the detection of PE. Both CTA and MRA are highly specific for PE detection and demonstrate high interobserver agreement. MPR/3D-SSD did not increase CTA performance over axial images alone.     

64层螺旋CT肺动脉造影在肺动脉栓塞诊断中的应用

目的 探讨64层螺旋CT肺动脉造影(CT pulmonary angiography,CTPA)对肺动脉栓塞(pulmonary embolism,PE)的诊断价值.方法 回顾分析24例肺动脉栓塞患者的64层螺旋CT增强图像,将原始图像复制到EBW4.0工作站,对肺动脉主干及分支进行多平面重建(MPR),最大密度投影(MIP)及容积重建(VR)分析.结果 24例患者中,共检出了76处肺动脉及其分支的栓子.其中,左、右肺动脉主干14处(右主干10处、左主干4处),肺叶动脉24处,肺段动脉26处,亚肺段动脉12处.CT表现为肺动脉主干或分支内混合性、附壁性、中心性充盈缺损,可分为完全性或部分性.结论 64层CTPA具有准确、高效、无创等优点,可直观、立体地观察到肺动脉血栓的大小、分布、范围及类型,是临床诊断及观察疗效的首选方法,有望成为肺动脉栓塞检查的“金标准”.     

ECG-gated multislice spiral CT for diagnosis of acute pulmonary embolism

AIM: The purpose of this study was to determine the feasibility of echocardiogram (ECG)-gated multi-slice CT angiography (MCTA) in patients with clinical suspicion of acute venous thromboembolism (VTE), to investigate the effect of ECG-gating on cardiac motion artefacts, and to determine the diagnostic reader agreement of ECG-gated MCTA in comparison with conventional MCTA. MATERIALS AND METHODS: Forty-eight consecutive patients were prospectively enrolled and randomly underwent ECG-gated (n=25, group 1) or non-ECG-gated (n=23, group 2) eight-slice pulmonary MCTA. Image data were evaluated by three independent chest radiologists with respect to the presence or absence of emboli at different arterial levels (main, lobar, segmental, and subsegmental arteries), and with regard to cardiac motion artefacts. Statistical tests used to calculate inter-observer agreement were weighted kappa statistics, extended kappa statistics and confidence indices indicating three-reader agreement accuracy. RESULTS: Twenty-seven patients (56.3%) were diagnosed to have pulmonary embolism (13 from group 1, 14 from group 2). Cardiac motion artefacts were significantly more frequent in group 2 (70% in group 2 versus 13% in group 1, p=0.0001). The overall diagnostic agreement was excellent with both MCTA techniques (three-reader confidence index for all vascular territories: 0.76 and 0.84 for groups 1 and 2, respectively (extended kappa=0.69 and 0.78, respectively); three-reader confidence index for diagnosis of VTE: 0.94 and 0.85 for groups 1 and 2, respectively (extended kappa=0.91 and 0.73, respectively), weighted kappa=0.81-0.83 and 0.92-0.95 for groups 1 and 2, respectively, and did not differ significantly between the two groups. In addition there was no significant difference of inter-observer agreement in either group at any assessed pulmonary arterial level. CONCLUSION: ECG-gated pulmonary MCTA is feasible in patients with clinical suspicion of VTE. However, ECG-gated image acquisition did not influence the diagnostic reader agreement accuracy and inter-observer agreement of MCTA. Hence, it does not appear to be advantageous for the MCTA diagnosis of pulmonary embolism.     

螺旋CT肺动脉造影对肺栓塞的诊断

目的：评价螺旋CT及其肺动脉造影诊断肺动脉栓塞（PE）的价值。方法：回顾性分析12例PE患,均行螺旋CT容积扫描,并在工作站进行图像后处理,获得肺动脉多平面重建图像及三维立体图像。结果：对12例196支肺动脉分支进行分析,受累率为46.4%;栓子发生在主肺动脉、左右肺动脉干及叶段肺动脉。多平面重建图像上表现为充盈对比剂血管内有充盈缺损区,或其远侧方无对比剂充填区。肺动脉成像示,主干血管内可见充盈缺损影,或呈截断状影;叶栓塞或段栓塞亦呈突然“截断状”,其远侧方肺动脉分支不显影或呈纤维状。结论：螺旋CT肺动脉造影不仅可以获得轴位图像,而且可以获得立体图像,可多轴向旋转观察PE部位,是诊断叶或段以上PE可靠而直观的检查方法。     

Validity of pulmonary cine arteriography for the diagnosis of pulmonary embolism

The aim of this study was to assess the interobserver variations in diagnosis of pulmonary embolism (PE) with cine technique and to compare the diagnostic accuracy of pulmonary arteriograms to final-outcome diagnosis. One hundred and seventy patients with clinical suspicion of acute PE were examined with ECG, laboratory tests, chest X-ray, pulmonary scintigraphy and selective pulmonary cine arteriography. The follow-up time was 6 months. Fifty-one arteriograms were interpreted as positive for PE. Two pulmonary emboli were missed when compared with the diagnosis as stated by the final-outcome committee. No arteriograms were considered as not of diagnostic quality. Mean interobserver agreement in lobar vessels was 100 %, in segmental vessels 93 % and in subsegmental vessels 63 %. The mean interobserver agreement was 89 %. Pulmonary cine arteriography produces high diagnostic accuracy and few inconclusive results in patients with suspected PE. Received: 29 September 1997; Revision received: 9 March 1998; Accepted: 14 July 1998     

Computed tomography pulmonary angiogram diagnosis of pulmonary embolism

Over the last decade, contrast-enhanced spiral CT has been established as a non-invasive alternative to catheter angiography and is now regarded as the first-line imaging investigation for the diagnosis of pulmonary embolism (PE). The reported sensitivities for the diagnosis of PE of spiral CT vary from 45 to 100% and the specificities vary from 78 to 100%. Prospective outcome studies have shown a high negative predictive value for a single-detector spiral CT for PE. Patients' outcomes were not adversely affected in these studies when anticoagulation was withheld after a negative CT pulmonary angiogram. The main limitation of single-detector spiral CT has been its limited ability to detect isolated subsegmental PE. However, multidetector spiral CT allows evaluation of pulmonary vessels down to sixth-order branches and significantly increases the rate of detection of PE in segmental and subsegmental levels. The interobserver correlations for diagnosis of subsegmental PE with multidetector spiral CT exceed the reproducibility of selective pulmonary angiography. If appropriate equipment is available (multidetector CT), then CT pulmonary angiogram is safe to be used as the first-line imaging investigation for the diagnosis of PE.     

实验性急性肺栓塞的比较影像学研究

目的　探讨核素肺灌注显像、增强螺旋CT及数字减影肺动脉造影对猪急性肺栓塞实验模型 (相当于人类亚肺段水平肺栓塞 )的影像学特点。方法　 13头中国实验用小型猪 ,经颈静脉注射明胶海绵栓子 (直径 3 8～ 4 2mm) ,制作肺栓塞模型后进行核素肺灌注显像、增强螺旋CT和数字减影肺动脉造影 ,以病理检查为标准 ,比较 3种检查方法的灵敏度和特异性。结果　对 195个肺段(动脉段 )进行分析 ,病理诊断阳性肺段 4 6个 ,阴性肺段 14 9个。核素肺灌注显像阳性肺段 5 1个 (包括假阳性肺段 11个 ) ,灵敏度为 87% ,特异性为 93% ;增强螺旋CT阳性肺段 4 4个 (包括假阳性肺段15个 ) ,灵敏度为 6 3% ,特异性为 90 % ;数字减影肺动脉造影阳性肺段 4 7个 (包括假阳性肺段 2个 ) ,灵敏度为 98% ,特异性为 99%。核素肺灌注显像病变检出率比增强螺旋CT高 (P <0 0 5 ) ,但与数字减影肺动脉造影相比差异无显著性 (P >0 0 5 )。增强螺旋CT可对栓子进行准确定位。结论　核素肺灌注显像对猪肺段 (相当于人类亚肺段 )肺栓塞的探测优于增强螺旋CT ,而后者对栓子定位优于前者 ;数字减影肺动脉造影对猪肺段肺栓塞诊断能力最强 ,但有创 ,应用受限。     

Pulmonary embolism: prospective comparison of iso-osmolar and low-osmolarity nonionic contrast agents for contrast enhancement at CT angiography

PURPOSE: To prospectively evaluate contrast enhancement on pulmonary computed tomographic (CT) angiograms obtained by using an iso-osmolar versus a low-osmolarity contrast agent to exclude pulmonary embolism. MATERIALS AND METHODS: Written patient consent was obtained on a form approved by the institutional review board, and the board approved the study. This prospective, randomized, double-blinded clinical trial included 47 patients referred for multi-detector row CT angiography to exclude pulmonary embolism over a 5-month period. Patients received either iohexol or iodixanol as an intravenous contrast agent. Three radiologists independently evaluated enhancement homogeneity and quality in designated pulmonary artery branches at four consecutive levels in the lower lobe of the left lung from lobar to subsegmental arteries. This evaluation was performed at a workstation separately for homogeneity and quality with two different three-level scales established with consensus. Percentages of each given score were compared with the chi2 test. The mean attenuation (expressed in Hounsfield units) for each contrast agent was compared with Student t test, and interobserver agreement (kappa value) was calculated. RESULTS: The percentages of arteries graded as excellent or not diagnostic were not statistically different (P >.05), with comparison of the two contrast agents at all levels. The intensity of enhancement (quantitative evaluation of enhancement by using mean attenuation of vessel lumen) was similar (P >.05) in the two groups. The kappa values varied from 0.35 to 0.56 among readers. CONCLUSION: Use of an iso-osmolar contrast agent at multi-detector row CT angiography to exclude pulmonary embolism did not significantly improve enhancement quality when this feature was compared with that of a low-osmolarity contrast agent.     

CT肺动脉成像诊断肺栓塞的一致性研究

目的评价CT肺动脉成像（CTPA）诊断肺栓塞（PE）时,不同经验的读片者间和同一读片者内的一致性。方法 55例临床可疑PE患者行CTPA检查,6位不同经验的放射科医生独立地分析CTPA图像来评价读片者间的一致性。3位放射科医生3个月后第二次分析CTPA图像来评价读片者内的一致性。PE的表现分为阳性、阴性和难以确定。读片者一致性用百分比及Kappa系数表示。结果 6位读片者判定29～31例（平均29.2例）患者CTPA为PE阳性,1～5例（平均3.0例）患者CTPA为难以确定。6位读片者在48例（87.3%）患者CTPA的诊断上取得一致意见,5位读片者在4例患者（7.3%）的诊断上取得一致意见,4位读片者在2例患者（3.6%）的诊断上取得一致意见,3位读片者在1例患者（1.8%）的诊断上取得一致意见。在诊断PE上,如果以每例患者为观察单位,读片者间的一致性＂非常好＂（Kappa值为0.91）。以每个肺动脉为观察单位,读片者间的一致性＂好＂（85%,Kappa值为0.74）;以肺叶动脉为观察单位,读片者间的一致性＂好＂（89%,Kappa值为0.78）;以肺段动脉为观察单位,读片者间的一致性＂中等＂（75%,Kappa值为0.59）。如果以每例患者为观察单位,同一读片者内的平均一致性＂非常好＂（96%,Kappa值为0.93）。结论在CTPA上诊断PE时,经验不同的读片者间和同一读片者内的一致性均较好。     

增强螺旋CT和肺动脉造影在肺动脉栓塞诊断和治疗中的应用

目的 评价螺旋CT和肺动脉造影在肺动脉栓塞诊断和治疗中的作用。方法 回顾性分析经螺旋CT增强和肺动脉造影明确诊断的18例患者的影像资料。其中12例经肺动脉造影后，行导管抽吸和局部溶栓治疗。结果 18例患者累及107处肺动脉及其分支，双肺下叶主支受累最多，达28．97％，累及左、右肺动脉主干者占22．43％，累及肺叶以下分支达40．18％，累及主肺动脉者占8．41％。肺动脉栓塞的影像学直接征象包括部分性充盈缺损、附壁性充盈缺损、中心性充盈缺损（即“轨道征”）、完全阻塞，间接征象包括主肺动脉增宽、局限性肺纹理稀疏、肺梗死和胸腔积液。12例术后临床症状改善，动脉血氧分压增高。结论 螺旋CT增强扫描是一种有效的诊断肺动脉栓塞的无创性检查手段，且诊断率较高。     

Interobserver agreement in the diagnosis of pulmonary embolism with helical CT

PURPOSE: Our objective was to asses the interobserver agreement in the detection of pulmonary embolism (PE) with contrast-enhanced helical CT at the main pulmonary, lobar and segmental arteries. A prospective study was carried out in 51 patients with suspected PE. Finally, 29 patients were diagnosed of PE. SUBJECTS AND METHODS: All patients were studied with helical CT. Images (5 mm collimation, 1.5 pitch factor, 3 mm reconstruction interval) were obtained after bolus contrast injection (120 ml, 4 ml/s, 15 s delay time). All cases were blinded and independently interpreted in three ways: two radiologists with different level of expertise and two expert radiologists reading by consensus. Agreement was evaluated by means of the kappa test. RESULTS: Kappa values for thrombi detection expressed an excellent agreement at the main (between 0.802 and 0. 946), lobar (between 0.915 and 0.958) and segmental (between 0.879 and 0.718) levels. For all vessels, mean kappa values were similar and excellent for all three combinations of readers. Arteries with more discrepancies were located mainly at the anterior and posterior areas of the upper lobes. CONCLUSIONS: The high degree of agreement shown in this study indicates that helical CT is a reproducible test in the diagnosis of PE to the segmental level. Isolated readings and levels of expertise do not influence agreement.     

40层螺旋CT在肺动脉栓塞诊断中的应用价值

目的:探讨40层螺旋CT在肺动脉栓塞中的应用价值.方法:使用40层螺旋CT扫描机(Siemens Defination AS 40)对临床初步诊断肺动脉栓塞的38例患者进行研究.采用层厚5 mm行胸部增强扫描.利用3D后处理工作站进行重建为0.75 mm的轴面及多平面重建(MPR).比较层厚5 mm和1mm的轴面图像及MPR图像.结果:CT诊断肺动脉栓塞31例.病变共累计肺动脉260支.对于主肺动脉及肺叶动脉栓塞,3种图像检出结果一致.但对于肺段及亚段肺动脉栓塞的显示,层厚0.75 mm优于5 mm,差异有显著性意义(P<0.01),0.75 mm的MPR与轴面图像间差异无显著性意义(P＞0.05).结论:40层螺旋CT在肺动脉栓塞诊断中具有无创、快速、敏感性高的优点,应当作为肺动脉栓塞的首选检查方法.     

Segmental and subsegmental pulmonary arteries: evaluation with electron-beam versus spiral CT

PURPOSE: To compare contrast agent-enhanced spiral and electron-beam computed tomography (CT) for the analysis of segmental and subsegmental pulmonary arteries. MATERIALS AND METHODS: CT angiography of the pulmonary arteries was performed in 56 patients to rule out pulmonary embolism. Electron-beam CT was performed in 28 patients. The other 28 patients underwent spiral CT with comparable scanning protocols. The depiction of segmental and subsegmental arteries was analyzed by three independent readers. The contrast enhancement in the main pulmonary artery was measured in each patient. RESULTS: Analysis was performed in 1,120 segmental and 2, 240 subsegmental arteries. One segmental (RA7, P =.010) and two subsegmental (LA7b, P =.029; RA6a+b, P =.038) arteries in paracardiac and basal segments of the lung were depicted significantly better with electron-beam CT. There was no statistically significant difference between electron-beam and spiral CT in the total number of analyzable peripheral arteries depicted. The mean contrast enhancement in the main pulmonary artery was 362 HU in electron-beam CT studies versus 248 HU in spiral CT studies. CONCLUSION: Detailed visualization of peripheral pulmonary arteries is well within the scope of advanced CT techniques. Electron-beam CT has minor advantages in analyzing paracardiac arteries, probably because of reduction of motion artifacts and higher contrast enhancement. Further studies are needed to establish whether electron-beam CT allows a more confident diagnosis of emboli in these vessels.     

Pulmonary embolism revealed on helical CT angiography: comparison with ventilation-perfusion radionuclide lung scanning

OBJECTIVE: We compared helical CT angiography and ventilation-perfusion radionuclide lung scanning as initial tests in the diagnosis of acute pulmonary embolism. SUBJECTS AND METHODS: Two hundred sixteen consecutive patients who were clinically suspected of having acute pulmonary embolism underwent helical CT angiography, ventilation-perfusion radionuclide lung scanning, and Doppler sonography of the veins of the legs. On the basis of concordance of the results for ventilation-perfusion radionuclide lung scanning and helical CT angiography and on the degree of clinical suspicion, certain patients underwent pulmonary angiography. Patients without pulmonary embolism at initial evaluation in whom no treatment was instituted were followed up for at least 3 months to determine the potential recurrence of thromboembolic disease. RESULTS: Of the 216 patients, 37 (17%) were excluded because of insufficient data to assess the initial event. Final diagnosis for the 179 remaining patients was pulmonary embolism in 68 (37.9%) and no pulmonary embolism in 111 (62.0%), based on pulmonary angiography in 23 patients (12.8%) and concordant imaging findings and outcome in the remaining patients. Statistically significant differences (p < 0.05) were found between sensitivity, specificity, positive predictive value, and negative predictive value for helical CT angiography and ventilation-perfusion radionuclide lung scanning (94.1% versus 80.8%; 93.6% versus 73.8%; 95.5% versus 82%; and 96.2% versus 75.9%, respectively). Interobserver agreement was excellent for helical CT angiography (kappa = 0.72) and moderate for ventilation-perfusion radionuclide lung scanning (kappa = 0.22). CONCLUSION: Helical CT angiography could replace ventilation-perfusion radionuclide lung scanning as the initial test for screening patients who are clinically suspected of having pulmonary embolism.     

Comparing the interpretations of CT pulmonary angiograms by attending and resident radiologists: can residents identify life-threatening pulmonary emboli in hospitalized patients?

Objective: CT pulmonary angiography is now often the first-line investigation for pulmonary emboli. When these studies are performed after hours in teaching hospitals, they are often initially interpreted by trainees. It is of great significance whether the interpretations of trainees and certified radiologists with regard to the presence of pulmonary emboli on CT pulmonary angiograms correspond, because of the morbidity and mortality of both the condition and its treatment. Material and methods: Twenty-five consecutive CT pulmonary angiograms (CTPAs) of hospitalized patients were viewed at lung and soft tissue windows both on a workstation and on hard copies, at the observers' discretion. Each CTPA was divided into 28 arterial zones based on pulmonary anatomy (including the subsegmental arteries), giving a total of 700 arterial zones, and analyzed retrospectively and independently by two cross-sectional imaging specialists and four residents. Each arterial segment was rated with regard to pulmonary embolus as either high, intermediate, or low probability or not visualized. The kappa (Κ) test, which tests for interobserver agreement, was used for statistical analysis. Results: At the time of the scan all patients were hospitalized for underlying conditions. Of the 25 patients studied, 9 were referred from the ICU, 7 experienced severe acute shortness of breath and respiratory failure, 5 were post-partum women, 2 had had a recent stroke, 1 patient had antithrombin III deficiency, and 1 had a diagnosis of breast cancer. The incidence of pulmonary emboli was 44%. For the main pulmonary arteries interobserver agreement was good (Κ=0.61) and for the segmental pulmonary arteries it was fair (Κ=0.26). For the subsegmental arteries interobserver agreement was poor (Κ=0.16). The zones where interobserver agreement was greatest (Κ>0.4) were the left main, left lower lobe, and the right main pulmonary arteries. Interobserver agreement was poorest (Κ<0.05) in the left interlobar, left lower lobe lateral basal segment, right lower lobe superior segment, and left lower lobe superior segment branches. None of the patients expired due to pulmonary emboli. Conclusion: Most life-threatening pulmonary emboli requiring urgent treatment are the more central emboli. This study demonstrates that trainees and certified radiologists can make similar conclusions regarding these central pulmonary emboli in hospitalized patients and that preliminary interpretations by trainees should not therefore adversely affect patient care. Electronic Publication