CT for thromboembolic disease

Pulmonary embolism (PE) and deep venous thrombosis (DVT) constitute the two clinical manifestations of venous thromboembolic disease (VTE). The recent innovation of computed tomography venography (CTV) in conjunction with CT pulmonary arteriography (CTPA) provides a single noninvasive diagnostic test that can evaluate both components of VTE. PE is often an underestimated, underdiagnosed, and, consequently, undertreated disease entity. Herein, we review the epidemiology of thromboembolic disease, the diagnostic algorithm used in evaluation of patients with suspected VTE, and protocols for performing CTPA and CTV. Interpretation of these examinations is discussed in detail, because CTPA may pose new challenges to the practicing radiologist.     

CT venography vs ultrasound in the diagnosis of thromboembolic disease in patients with clinical suspicion of pulmonary embolism

To assess the reliability of indirect computed tomography venography (CTV) in the detection of deep venous thrombosis (DVT) in patients with clinical suspicion of pulmonary embolism (PE). 235 consecutive patients with suspicion of PE underwent an imaging protocol composed of a CT pulmonary angiography (CTPA), a CTV and an ultrasound study of the deep venous system, which was considered the “gold standard.” Sensitivity, specificity, and predictive values were calculated for CTV. ith CTV, 30 (12.8%) cases of DVT were detected, 9 (3.8%) of them without pulmonary embolism in CTPA, increasing the diagnosis of thromboembolic disease in 3.8%. However, six of these nine diagnoses were false positives, and CTV missed six cases of DVT. CTV rendered a sensitivity of 58.8%, specificity of 95.0%, a positive predictive value of 66.7%, and a negative predictive value of 93.2%. In patients with clinical suspicion of pulmonary embolism, ultrasound is preferred to CTV for the detection of DVT.     

Indirect computed tomography venography: a report of vascular opacification

The clinical utility of indirect computed tomography venography (CTV) of the legs, performed after computed tomography pulmonary angiography (CTPA), to evaluate for deep venous thrombosis (DVT) remains a subject of ongoing debate. Visualization of DVT on CTV requires adequate opacification of venous blood. The objective of this study is to measure the Hounsfield unit (HU) clot-to-blood gradient on CTV and CTPA. Secondary analysis of computed tomography images from a prospective clinical trial was performed. All images were interpreted independently by a radiologist. Using the “region of interest” tool feature of the picture archiving and communication system, observers measured the HU of blood and thrombus on CTPA and CTV, using a structured anatomic approach. Interobserver coefficient of variability (CV%) was examined in all disease-positive cases and in a random sample of 25 disease-negative cases. One hundred seventy-nine patients were enrolled; and 23 had pulmonary embolus (PE) without DVT (13%), one had DVT without PE (0.6%), and 18 had both (10%), leaving 137 (77%) who had no venous thromboembolism (VTE). For the 137 patients with no VTE, the mean (±standard deviation) HU values measured for contrast-containing blood with no thrombus were as follows: left and right main pulmonary arteries (MPA), 291 ± 73 and 291 ± 76; left and right common femoral vein (CFV), 92 ± 17 and 88 ± 19; and left and right popliteal vein (PV), 87 ± 20 and 84 ± 20. On CTPA, the HU measured from the filling defects interpreted as acute PE was 51 ± 20, suggesting a between-group HU gradient of 250 or 471% for MPA (PE-to-blood). On CTV, the HU for DVT was 63, suggesting a gradient of 27 HU or 43% for CFV (DVT-to-blood) and 23 HU or 37% for PV (DVT-to-blood). Interobserver CV% were: left and right MPA, 5 ± 4.0% and 7 ± 5.4%; left and right CFV, 7 ± 6.8% and 7 ± 7.3%; left and right PV, 7 ± 8.4%, 6 ± 8.2%, and 32 ± 27.1% for PE thrombus, and 20 ± 30.5% for DVT thrombus. CTV imaging produces a very small HU gradient between clot and blood in leg veins. These findings highlight the importance of ancillary radiological findings in assessing presence of DVT on CTV.     

Comparison of on-call radiology resident and faculty interpretation of 4- and 16-row multidetector CT pulmonary angiography with indirect CT venography

RATIONALE AND OBJECTIVES: On-call radiology residents frequently interpret computed tomography (CT) pulmonary angiography and CT venography studies outside of routine working hours. The purpose of this study was to compare resident and faculty interpretation concordance rates and to see if concordance rates differed depending on the number of CT detectors used. MATERIALS AND METHODS: The study population included 122 consecutive CT pulmonary angiography (CTPA) and CT venography (CTV) examinations performed on a four-row multidetector CT (MDCT) and 125 consecutive CTPA examinations performed using a 16-row MDCT scanner with CTV performed in 124 patients. Preliminary resident reports and final faculty reports were compared. Discrepant cases were independently reviewed by three cardiothoracic radiologists who were unaware of the initial interpretations. Interpretation concordance rates were calculated for both 4- and 16- row MDCT studies and compared using Fisher's exact test. RESULTS: Resident and faculty CTPA and CTV interpretations were concordant in 80% of the 4-row cases and 94% of the 16-row cases. When comparing resident interpretation to the final expert reference standard, the corrected resident error rate was 11% and 2% for 4-row CTPA and CTV, respectively and 4% and 2% for 16-row CTPA and CTV, respectively. Overall CTPA and CTV concordance was significantly lower for 4-row MDCT (80% versus 94%, P < .001 [two-sided] by Fisher's exact test). CONCLUSIONS: Radiology resident interpretation of CTPA and CTV studies demonstrates a high level of agreement with radiology faculty interpretation. Concordance rates are significantly higher for 16-row MDCT than 4-row MDCT which may be due to improved image quality.     

CT lower extremity venography in suspected pulmonary embolism in the ED

The purpose of this study was to evaluate the added benefit of computed tomography lower extremity venography (CTLV)—performed following CT pulmonary angiography (CTPA)—in the emergency department (ED) patient suspected of pulmonary embolism (PE). A retrospective review of 427 consecutive patients having both CTPA and CTLV performed to evaluate patients suspected of PE at two community hospitals was conducted. Three-month follow-up was performed on all patients to ensure that no case of PE or deep venous thrombosis (DVT) was missed. Forty patients were positive for PE, and 11 were positive for DVT. There were 6 CTPA studies read as indeterminate for PE and 11 CTLV studies indeterminate for DVT. Only 1 patient was positive for DVT, who did not have a concurrent PE identified by CTPA. The estimated charges for detecting the single case of isolated DVT was US $206,400. In our ED setting, the additional benefit of adding CTLV to the standard ED work-up of PE was minimal.     

Venous thromboembolism: additional diagnostic value and radiation dose of pelvic CT venography in patients with suspected pulmonary embolism

Purpose

To assess the additional diagnostic value of indirect CT venography (CTV) of the pelvis and upper thighs performed after pulmonary CT angiography (CTA) for the diagnosis of venous thromboembolism (VTE).

Materials and methods

In a retrospective analysis, the radiology information system entries between January 2003 and December 2007 were searched for patients who received pulmonary CTA and additional CTV of the pelvis and upper thighs. Of those patients, the radiology reports were reviewed for the diagnosis of pulmonary embolism (PE) and deep venous thrombosis (DVT) in the pelvic veins and veins of the upper thighs. In cases with an isolated pelvic thrombosis at CTV (i.e. which only had a thrombosis in the pelvic veins but not in the veins of the upper thigh) ultrasound reports were reviewed for the presence of DVT of the legs. The estimated radiation dose was calculated for pulmonary CTA and for CTV of the pelvis.

Results

In the defined period 3670 patients were referred to our institution for exclusion of PE. Of those, 642 patients (353 men, 289 women; mean age, 65 ± 15 years, age range 18–98 years) underwent combined pulmonary CTA and CTV. Among them, PE was found in 227 patients (35.4%). In patients without PE CTV was negative in all cases. In patients with PE, CTV demonstrated pelvic thrombosis in 24 patients (3.7%) and thrombosis of the upper thighs in 43 patients (6.6%). Of those patients 14 (2.1%) had DVT in the pelvis and upper thighs. In 10 patients (1.5%) CTV showed an isolated pelvic thrombosis. Of those patients ultrasound reports were available in 7 patients, which revealed DVT of the leg veins in 5 cases (1%). Thus, the estimated prevalence of isolated pelvic thrombosis detected only by pelvic CTV ranges between 1–5/642 patients (0.1–0.7%). Radiation dose ranges between 4.8 and 9.7 mSv for additional CTV of the pelvis.

Conclusion

CTV of the pelvis performed after pulmonary CTA is of neglectable additional diagnostic value for the detection of VTE, because the additional radiation dose is high and isolated pelvic DVT is very rare. Venous imaging of the legs (preferably by radiation-free ultrasound) is sufficient for the diagnosis of underlying DVT in patients with suspected PE.     

肺栓塞和下肢深静脉血栓的多层CT联合成像

目的：探讨下肢深静脉血栓和肺栓塞的多层CT联合成像的诊断价值,并分析下肢深静脉血栓与肺栓塞的相关性。方法：对临床疑诊肺栓塞和/或下肢深静脉血栓的连续80例患者行CT肺动脉和下肢深静脉联合成像,采用16层CT,1.25mm×16模式采集,注射对比剂120ml,注射流率3～4ml/s,肺动脉延迟20～25s扫描,下肢静脉延迟150～180s扫描。结果：共发现下肢深静脉血栓52例55侧,肺栓塞21例37侧,其中肺栓塞和下肢深静脉血栓同时存在18例。结论：肺栓塞与下肢深静脉血栓关系密切,多层螺旋CT肺动脉和下肢静脉联合成像可一次性评价肺动脉和下肢静脉,是肺栓塞适宜的检查方法。     

A retrospective study of the value of indirect CT venography: a British perspective

Objective

The aim of this study was to establish the value of indirect CT venography (CTV) in clinical practice within the UK.

Methods

804 combined CT pulmonary angiogram and CTV studies were retrospectively reviewed. CTV was performed 180 s after the injection of contrast using an incremental technique with a 5-mm collimation and a 5-cm interspace between images extending from the iliac crests to the tibial plateaus.

Results

12.9% of studies had isolated pulmonary emboli (PE), 3.0% had both a PE and deep vein thrombosis (DVT) and 1.1% had an isolated DVT. The proportion of positive cases diagnosed by CTV alone was 6.6%.

Conclusion

In a UK-based practice, the incidence and the proportion of isolated DVT diagnosed by CTV are lower than expected from published data. An analysis of possible causes for this is made within the paper.More than 250 000 cases of pulmonary embolism were identified in the UK between 1996 and 2006, yet the accurate diagnosis of this condition remains problematic [1]. Autopsy studies indicate that 88% of pulmonary emboli (PE) are unsuspected clinically prior to death. Although the majority of these PE are an incidental complication of an underlying comorbid condition, less than half of cases of fatal PE are correctly diagnosed ante-mortem [2,3]. It is accepted that PE originate from distant sites of venous thrombosis and that both PE and deep vein thrombosis (DVT) are facets of the same disease process, with the majority of DVT arising within the lower limb veins. The evaluation of the presence of DVT is therefore considered part of the investigation of PE, and the presence of DVT in the absence of radiological evidence of PE can be accepted as surrogate evidence of venous thromboembolism (VTE). Lower limb indirect CT venography (CTV) may be added to CT pulmonary angiography (CTPA) to identify the presence of DVT, but this is at the expense of an increased examination time and an increased radiation dose, particularly to the reproductive organs. The prospective investigation of the PE diagnosis II study demonstrated the addition of CTV to CTPA increased the sensitivity for detection of PE from 83% to 90% [4]. Despite this, the routine addition of CTV to CTPA is not recognised in current British Thoracic Society guidelines, and it is not known how many centres in the UK have adopted this technique [5].The aim of this study is to establish the incremental value of CTV in clinical practice within a British institution and ascertain whether factors such as image quality significantly influence the value of the examination. To our knowledge this is the first large British study of the value of CTV in the investigation of PE.     

Does addition of CT pelvic venography to CT pulmonary angiography protocols contribute to the diagnosis of thromboembolic disease?

AIM: To evaluate the contribution which addition of pelvic computed tomography venography (CTV) to a standard CT pulmonary angiography (CTPA) imaging protocol makes to a definitive diagnosis of thromboembolic disease. MATERIALS AND METHODS: One hundred and six consecutive patients over the age of 55 years referred for (CTPA) for suspected pulmonary embolism between June and November 1999 had pelvic CTV performed at the time of the CTPA study. RESULTS: Ninety-six of 106 CTPA studies were technically adequate. In total, 29/96 (29.6%) CTPA studies were positive for pulmonary embolism, 10/96 (10.4%) CTV studies were positive and five of these 10 examinations showed venous thrombus when the CTPA study was negative (n = 4) or equivocal (n = 1). CONCLUSION: Addition of CTV shows residual thrombus in the pelvis in a proportion of patients with positive CTPA studies and demonstrates venous thrombus in a small number of patients with no CT evidence of pulmonary embolism.     

Computed tomography pulmonary angiography with pelvic venography in the evaluation of thrombo-embolic disease

A prospective study was performed to evaluate the usefulness of CT pelvic venography (CTV) in the detection of pelvic vein thrombosis in patients referred for CT pulmonary angiography (CTPA) for suspected pulmonary embolism. Fifty consecutive patients referred for CTPA had CTV performed at the time of CTPA. All patients had duplex ultrasound (DUS) of the lower limb veins for evaluation of deep venous thrombosis (DVT) within 24 h of the CT study. Twelve (24%) of the 50 patients had pulmonary embolism diagnosed on CTPA. Associated DVT was detected in six of these patients; two cases were detected by CTV alone, while one case was detected by both CTV and DUS. The remaining three cases had DVT diagnosed by DUS alone. In the 38 patients with a negative CTPA, three patients had venous thrombus diagnosed by CTV. Of these three patients, two had a negative DUS study. CTV therefore led to a definitive imaging diagnosis of thrombo-embolic disease in two (4%) more patients. CTV adds little time and cost to the CTPA examination and leads to a moderate increase in definite imaging diagnosis of thrombo-embolic disease.     

肺动脉栓塞的CT血管造影检查

目的研究CT肺动脉血管造影联合下肢深静脉血管造影在肺栓塞的诊断中的作用及多层螺旋CT的优势。方法采用单层螺旋CT或16层螺旋CT对临床拟诊肺栓塞的所有患者行肺动脉血管造影(CTPA)及下肢静脉血管造影,统计栓塞的数目及类型。结果44例肺栓塞中,肺栓塞合并下肢静脉栓塞的34例,单纯肺栓塞的10例。单层螺旋CT及16层螺旋CT检查的病人总的栓塞显示率分别为12.1%及19.0%,差异有统计学意义(P=0.004);肺段及肺段以上肺动脉栓塞的显示率分别为25.3%及29.7%,差异无统计学意义(P=0.104);亚段及亚段以下显示率分别为1.1%及10.2%,差异有统计学意义(P=0.000)。结论CT肺动脉血管造影联合下肢血管造影是肺栓塞的无创、快速、敏感性和特异性均较高的诊断方法。16层螺旋CT在检查肺栓塞方面优于单层螺旋CT。     

Intraindividual comparison of gadolinium- and iodine-enhanced 64-slice multidetector CT pulmonary angiography for the detection of pulmonary embolism in a porcine model

This study is an evaluation of the diagnostic accuracy of gadolinium-enhanced computed tomography pulmonary angiography (CTPA) for the detection of pulmonary embolism (PE) in comparison with iodine-enhanced CTPA. PE was induced in five anesthetized pigs by administration of blood clots through an 11-F catheter inside the jugular vein. Animals underwent CTPA in breathhold with i.v. bolus injection of 50 ml gadopentetate dimeglumine (0.4 mmol/kg, 4 ml/s). Subsequently, CTPA was performed using the same imaging parameters but under administration of 70 ml nonionic iodinated contrast material (400 mg/ml, 4 ml/s). All images were reconstructed with 1 mm slice thickness. A consensus readout of the iodium-enhanced CTPAs by both radiologists served as reference standard. Gadolinium-enhanced CTPAs were evaluated independently by two experienced radiologists, and differences in detection rate between both contrast agents were assessed on a per embolus basis using the Wilcoxon signed-rank test. Interobserver agreement was determined by calculation of қ values. PE was diagnosed independently by both readers in all five pigs by the use of gadolinium-enhanced CTPA. Out of 60 pulmonary emboli detected in the iodine-enhanced scans, 47 (78.3%; reader 1) and 44 (62.8%; reader 2) emboli were detected by the use of gadolinium. All 13 (100%) emboli in lobar arteries (by both readers) and 26 (reader 1) and 25 (reader 2) out of 27 emboli (96.3% and 92.6%) in segmental arteries were detected by the use of the gadolinium-enhanced CTPA. In subsegmental arteries, only 8 (40%; reader 1) and 6 (30%; reader 2) out of 20 emboli were detected by the gadolinium-enhanced CTPA. By comparing both scans on a per vessel basis (Wilcoxon test), Gd-enhanced CTPA was significantly inferior in emboli detection on subsegmental level (P < 0.0001). The interobserver agreement was excellent on lobar and segmental level (қ = 1.0 and 0.93, respectively), whereas readers only reached moderate agreement for PE evaluation on subsegmental level (қ = 0.56). Compared to conventional CTPA with iodinated contrast media, gadolinium-based contrast agents achieve an equivalent diagnostic accuracy in detection of PE down to segmental level. Gadolinium-enhanced CTPA may be considered as an alternative for the diagnostic workup of acute pulmonary embolism in patients with contraindications to iodinated contrast agents.     

80kV条件下碘克沙醇（270mgI/mL）在CTPA检查中的研究

目的：探讨80 kV 条件下碘克沙醇(270 mg I/mL)应用于 CT 肺动脉血管成像(CTPA)检查的可行性。方法将90例拟行 CTPA 检查的患者随机分为 A 组和 B 组。A 组45例：应用270 mg I/mL 碘对比剂同时使用自适应统计迭代重建(ASIR),管电压为80 kV,自动 mA;B 组45例：应用370 mg I/mL 碘对比剂同时使用滤波反投影(FBP)重建,管电压为120 kV,自动 mA。2组使用对比剂的总量均为40 mL。记录2组的容积 CT 剂量指数(CTDI)、剂量长度乘积(DLP)。对2组图像质量进行双盲法评分;采用两独立样本 t 检验比较2组患者的有效辐射剂量、平均 CT 值、图像噪声、图像信噪比(SNR)、对比噪声比(CNR)、图像质量评分等,并对2组患者的阳性率以及碘摄入量进行比较。结果CTPA 共检查出肺动脉栓塞(PE)53例(A 组24例,B 组29例),A组显示 PE 的阳性率(53.33%)与 B 组(64.44%)差异均无统计学意义。2组均可以显示4~6级肺动脉分支,图像质量均符合诊断要求,主观评分的差异无统计学意义(P >0.05)。2组患者的性别、年龄和体质量指数(BMI)的差异均无统计学意义。A 组的肺动脉平均 CT 值和噪声分别高于 B 组,差异有统计学意义(P <0.01)。A 组的 SNR 和 CNR 低于 B 组,差异有统计学意义(P <0.01)。结论在80 kV 条件下应用碘克沙醇(270 mg I/mL)行 CTPA 检查,获得的图像可满足临床需求,降低了辐射剂量并减少了对比剂的摄入量。     

Combined helical computed tomographic pulmonary angiography and lung perfusion scintigraphy for investigating acute pulmonary embolism.

AIM: To evaluate a diagnostic protocol incorporating helical computed tomographic pulmonary angiography (CTPA) and lung perfusion scintigraphy in the detection or exclusion of pulmonary embolism (PE) in routine clinical practice. MATERIALS AND METHODS: A prospective observational study of 808 consecutive patients with suspected acute PE was undertaken over a 23-month period. Twenty-nine cases who failed to follow the protocol were excluded, leaving 779 cases to be reviewed. The three main outcome measures were negative perfusion scintigraphy, positive CTPA and other significant abnormalities demonstrated on CT. RESULTS: Two hundred and thirty-one (30%) had negative perfusion scintigraphy and no further investigation. CTPA was performed in 548 (70%) and PE confirmed in 193 (25% of all patients). Other significant abnormalities were demonstrated in 25 (3%). CTPA was technically inadequate in 15 (2%). CONCLUSIONS: A confident conclusion was achieved in 449 cases (58%), with PE excluded in 231 (30%), proved in 193 (25%), and relevant alternative abnormalities found in 25 (3%). This protocol using both perfusion scintigraphy and CTPA is practical and more effective than either investigation alone.     

双源CT肺动脉成像的低对比剂量优化研究

目的：探讨双源 CT 大螺距肺动脉成像在低对比剂量优化时的可行性。方法对80例疑似肺栓塞的患者行 CT 肺动脉造影(CTPA)检查。按照随机数表法分为 A、B 2组：A 组,常规组40例,对比剂50 mL,自动跟踪触发扫描;B 组,小剂量测试组40例,对比剂量=体质量×0.3 mL/kg。测量2组肺动脉 CT 值、动静脉 CT 差值、对比噪声比(CNR)、信噪比(SNR)、辐射剂量,进行两独立样本 t 检验。评价图像质量、肺栓塞诊断阳性率,进行卡方检验。结果2组肺栓塞诊断阳性率差异无统计学意义(P =0.655)。主观质量评分差异无统计学意义(P =0.174)。B 组与 A 组的肺动脉干 CT 值与左肺 SⅢ动静脉差值差异有统计学意义(P =0.001)。B 组与 A 组的肺动脉干 SNR、CNR 差异无统计学意义(P =0.250、0.203)。B 组有效辐射剂量明显低于 A 组,差异有统计学意义(P =0.001)。结论双源 CT 大螺距肺动脉成像低对比剂量优化时,在满足临床诊断肺栓塞的需要下,较大程度地减少了对比剂的用量。     

Improved visualization of the urinary tract in multidetector CT urography (MDCTU): analysis of individual acquisition delay and opacification using furosemide and low-dose test images

PURPOSE: To retrospectively analyze the reliability of opacification and image quality of a modified MDCTU examination protocol using furosemide and an individual acquisition delay by low-dose test images MATERIALS AND METHODS: Excretory phase images obtained from 4-row and 16-row MSCTU examinations in 103 patients (69 men, 34 women) were independently reviewed by two radiologists. MDCTUs were performed by using a low-dose furosemide iv injection. No fixed delay for urographic image acquisition was applied. Urographic timing was individually adjusted by performing low-dose test images of the distal ureters to display their current opacification. Image analysis included grading of opacification and image quality of the segmented collecting system. Average urographic delay was calculated. Stratified comparisons of mean scores were assessed. Interobserver kappa values were calculated. RESULTS: Calculated median scan delay for patients with normal creatine levels (n = 92) was 420 sec (mean 453 sec; SD, 121 sec). The median number of acquired test images was 2 (range 1-6 images). The analysis of opacification demonstrated that 97% of the ICS, 89% of the proximal, 86% of the middle, and 81% of the distal ureter segments showed opacification greater than 90%. 7.8% of the distal ureteral segments could not be visualized. Statistics did not show significant differences of opacification between proximal, middle, and distal ureteral segments (P > 0.05). Overall image quality of MSCTU showed to be high when latest test images indicated homogeneous bilateral contrasted ureters (Pearson correlation coefficient r= 0.81). Interobserver kappa values were 0.8 and 0.78. CONCLUSION: Furosemide and scan delay timing by means of test images for MDCTU proved to be a reliable procedure to reach improved opacification of the upper urinary tract. It features the individual adaption of MDCTU to the excretory rate of the kidneys.     

Correlation between the site of pulmonary embolism and the extent of deep vein thrombosis: evaluation by computed tomography pulmonary angiography and computed tomography venography

Purpose  

The aim of this study was to evaluate the relation between the sites of pulmonary embolism (PE) and deep vein thrombosis (DVT) by computed tomography pulmonary angiography (CTPA) and CT venography (CTV) of the pelvis and lower extremities.     

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.     

CT Pulmonary Angiography: Using Decision Rules in the Emergency Department

PurposeThe aim of this study was to assess the appropriateness of utilization and diagnostic yields of CT pulmonary angiography (CTPA), comparing two commonly applied decision rules, the pulmonary embolism (PE) rule-out criteria (PERC) and the modified Wells criteria (mWells), in the emergency department (ED) setting.MethodsInstitutional review board approval was obtained for this HIPAA-compliant, prospective–cohort, academic single-center study. Six hundred two consecutive adult ED patients undergoing CTPA for suspected PE formed the study population. The outcome was positive or negative for PE by CTPA and at 6-month follow-up. PERC and mWells scores were calculated. A positive PERC score was defined as meeting one or more criteria and a positive mWells score as >4. The percentage of CT pulmonary angiographic examinations that could have been avoided and the diagnostic yield of CTPA using PERC, mWells, and PERC applied to a negative mWells score were calculated.ResultsThe diagnostic yield of CTPA was 10% (61 of 602). By applying PERC, mWells, and PERC to negative mWells score, 17.6% (106 of 602), 45% (273 of 602), and 17.1% (103 of 602) of CT pulmonary angiographic examinations, respectively, could have been avoided. The diagnostic yield in PERC-positive patients was higher than in mWells-positive patients (10% [59 of 602] vs 8% [49 of 602], P < .0001). Among PERC-negative and mWells-negative patients, the diagnostic yields for PE were 1.9% (2 of 106) and 4% (12 of 273), respectively (P = .004). The diagnostic yield of a negative PERC score applied to a negative mWells score was 1.9% (2 of 103).ConclusionsThe use of PERC in the ED has the potential to significantly reduce the utilization of CTPA and misses fewer cases of PE compared with mWells, and it is therefore a more efficient decision tool.     

螺旋CT肺动脉与下肢静脉联合成像对静脉血栓栓塞症的诊断价值

目的评价螺旋CT肺动脉与下肢深静脉联合成像技术（CTVPA）对静脉血栓栓塞症（VTE）的诊断价值。方法对临床拟诊为肺栓塞（PE）的46例患者行CTVPA成像，先行肺动脉CT成像，后行下肢深静脉扫描，深静脉CT扫描范围从胭静脉至双肾静脉水平。结果46例患者中，CTVPA显示PE患者37例，下肢深静脉血栓（DVT）34例，两者同时存在者30例。37例PE均为多发肺动脉栓子，共累及动脉189支，其中，左右肺动脉主干栓子2．6％（5／189）支，叶动脉30．2％（57／189）支，段动脉50．2％（95／189）支。亚段及亚亚段肺动脉16．9％（32／189）支。34例DVT患者中，左侧20例，右侧12例，盆腔内静脉血栓2例。CTVPA成像检出率较CTPA高10．8％（4/37）。结论16层螺旋CT CTVPA可实现“一站式”检查，对评价肺动脉与下肢深静脉血栓栓塞性疾病有较高的敏感性与特异性。