Spiral computed tomography for acute pulmonary embolism

There is still considerable debate about the optimal diagnostic imaging modality for acute pulmonary embolism. If imaging is deemed necessary from an initial clinical evaluation such as d-dimer testing, options include nuclear medicine scanning, catheter pulmonary angiography, and spiral CT. In many institutions, spiral CT is becoming established as the first-line imaging test in daily clinical practice. With spiral CT, thrombus is directly visualized, and both mediastinal and parenchymal structures are evaluated, which may provide important alternative or additional diagnoses. However, limitations for the accurate diagnosis of small peripheral emboli, with a reported miss rate of up to 30% with single-slice spiral CT so far, have prevented the unanimous embrace of spiral CT as the new standard of reference for imaging pulmonary embolism. The clinical significance of the detection and treatment of isolated peripheral pulmonary emboli is uncertain. Evidence is accumulating that it is safe practice to withhold anticoagulation in patients with suspected pulmonary embolism on the basis of a negative spiral CT study. Remaining concerns about the accuracy of spiral CT for pulmonary embolism detection may be overcome by the introduction of multidetector-row spiral CT. This widely available technology has improved visualization of peripheral pulmonary arteries and detection of small emboli. The most recent generation of multidetector-row spiral CT scanners appears to outperform competing imaging modalities for the accurate detection of central and peripheral pulmonary embolism. In this review, we assess the current role and future potential of CT in the diagnostic algorithm of acute pulmonary embolism.     

Multidetector computed tomography for the diagnosis of acute pulmonary embolism

PURPOSE OF REVIEW: This review describes the accuracy of multidetector contrast-enhanced computed tomography (CT) for the diagnosis of acute pulmonary embolism, the role of clinical assessment and of venous phase imaging in combination with it, and the approach to the diagnosis. RECENT FINDINGS: The sensitivity of CT angiography was 83%, specificity 96% and positive predictive value 86%. Positive predictive values were 97% for pulmonary embolism in a main or lobar artery, 68% for a segmental vessel, and 25% for a subsegmental branch. A CT angiogram with concordant clinical probability assessment resulted in high predictive values, but with a discordant clinical probability, predictive value was low. The sensitivity for pulmonary embolism increased to 90% by using CT venography in combination with CT angiography.A negative D-dimer by the rapid enzyme-linked immunosorbent assay method with a low or moderate probability clinical assessment can safely exclude pulmonary embolism. Clinical probability assessment and D-dimer are recommended. In general, CT angiography in combination with CT venography is recommended, but the choice of diagnostic tests depends on the clinical situation. SUMMARY: The reliability of multislice CT angiography is enhanced by clinical assessment and CT venography used with it. Clinical assessment and D-dimer are recommended before imaging.     

Spiral CT for pulmonary embolism

Radiologic imaging for pulmonary embolism has been problematic. Ventilation perfusion scanning is frequently inconclusive; pulmonary angiography has been traditionally underused. Now spiral computed tomographic (CT) angiography provides a readily available, noninvasive test for pulmonary embolism. The accuracy of this examination is exceedingly high, so it should become the first-line test for pulmonary embolism. Recent investigations reveal a high negative predictive value for spiral CT, further proving its value. In addition, spiral CT provides an alternative diagnosis in a high percentage of patients. This article reviews current literature regarding the sensitivity, specificity, reliability, consistency, and cost-effectiveness of spiral CT.     

Idiopathic pulmonary fibrosis: a composite physiologic index derived from disease extent observed by computed tomography

In idiopathic pulmonary fibrosis, the quantitation of disease severity using pulmonary function tests is often confounded by emphysema. We have identified the composite physiologic index (CPI) most closely reflecting the morphologic extent of pulmonary fibrosis. Consecutive patients with a clinical/computed tomography (CT) diagnosis of idiopathic pulmonary fibrosis (n = 212) were divided into group I (n = 106) and group II (n = 106). The CPI was derived in group I (by fitting pulmonary function tests against disease extent on CT) and was tested in Group II. The formula for the CPI was as follows: extent of disease on CT = 91.0 - (0.65 x percent predicted diffusing capacity for carbon monoxide [DLCO]) - (0.53 x percent predicted FVC) + (0.34 x percent predicted FEV1). In group II, the CPI correlated more strongly with disease extent on CT (r2 = 0.51) than the individual pulmonary function test (DLCO the highest value, r2 = 0.38). A subanalysis demonstrated that the better fit of the CPI was ascribable to a correction of the confounding effects of emphysema. Mortality was predicted more accurately by the CPI than by a pulmonary function test in all clinical subgroups, including a separate cohort of 36 patients with histologically proven usual interstitial pneumonia (CPI, p < 0.0005; FVC, p = 0.002; PO2, p = 0.002). In conclusion, a new CPI, derived against CT and validated using split sample testing, is a more accurate prognostic determinant in usual interstitial pneumonia than an individual pulmonary function test.     

多层螺旋CT在肺动脉栓塞诊断中的应用进展

着重介绍多层螺旋CT在肺动脉栓塞诊断中的应用,多层螺旋CT在诊断肺动脉栓塞中与其他辅助检查手段相比的优越性.研究表明多层螺旋CT可准确、直观的显示肺动脉的解剖结构及其与周围空间的关系,是诊断肺动脉栓塞快速、准确、有效、无创的手段和方法.     

Diagnostic pathways in acute pulmonary embolism: recommendations of the PIOPED II investigators

Purpose

To formulate comprehensive recommendations for the diagnostic approach to patients with suspected pulmonary embolism, based on randomized trials.

Methods

Diagnostic management recommendations were formulated based on results of the Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) and outcome studies.

Results

The PIOPED II investigators recommend stratification of all patients with suspected pulmonary embolism according to an objective clinical probability assessment. D-dimer should be measured by the quantitative rapid enzyme-linked immunosorbent assay (ELISA), and the combination of a negative D-dimer with a low or moderate clinical probability can safely exclude pulmonary embolism in many patients. If pulmonary embolism is not excluded, contrast-enhanced computed tomographic pulmonary angiography (CT angiography) in combination with venous phase imaging (CT venography), is recommended by most PIOPED II investigators, although CT angiography plus clinical assessment is an option. In pregnant women, ventilation/perfusion scans are recommended by many as the first imaging test following D-dimer and perhaps venous ultrasound. In patients with discordant findings of clinical assessment and CT angiograms or CT angiogram/CT venogram, further evaluation may be necessary.

Conclusion

The sequence for diagnostic test in patients with suspected pulmonary embolism depends on the clinical circumstances.     

Diagnosis with helical CT and echocardiography of patients with suspected chronic thromboembolic pulmonary hypertension

Chronic Thromboembolic Pulmonary Hypertension (CTEPH) is a serious disease with a very high mortality after variable periods of time. Early diagnosis of CTEPH is critical because thromboendarterectomy can improve survival, hemodimamics and functional capacity. Based on our experience we have performed a review of diagnostic techniques. Echocardiography, pulmonary angiography, fiberoptic angioscopy, helical CT an MRI. For each diagnostic procedure we have analysed its accuracy, invasiveness and easiness of use. We conclude that currently the most useful techniques are echocardiography (to asses pulmonary hypertension), and helical CT which is a good alternative to pulmonary angiography and can detect very specific findings such as dilatation of central pulmonary arteries, eccentric localized thrombi and mosaic attenuation of the pulmonary parenchyma. Even more accurate findings can be expected by the use of multislice CT, which could allow to asses the degree of narrowing of the pulmonary vessels and bronchial circulation.     

Strategies incorporating spiral CT for the diagnosis of acute pulmonary embolism: a cost-effectiveness analysis

OBJECTIVE: To assess the cost-effectiveness of spiral CT for the diagnosis of acute pulmonary embolism. DESIGN: Computer-based cost-effectiveness analysis. PATIENTS: Simulated cohort of 1,000 patients with suspected acute pulmonary embolism (PE), with a prevalence of 28.4%, as in the Prospective Investigation of Pulmonary Embolism Diagnosis study. INTERVENTIONS: Using a decision-analysis model, seven diagnostic strategies were compared, which incorporated combinations of ventilation-perfusion (V/Q) scans, duplex ultrasound of the legs, spiral CT, and conventional pulmonary angiography. MEASUREMENTS AND RESULTS: Expected survival and cost (in Canadian dollars) at 3 months were estimated. Four of the strategies yielded poorer survival at higher cost. The three remaining strategies were as follows: (1) V/Q +/- leg ultrasound +/- spiral CT, with an expected survival of 953.4 per 1,000 patients and a cost of $1,391 per patient; (2) V/Q +/- leg ultrasound +/- pulmonary angiography (the "traditional" algorithm), with an expected survival of 953.7 per 1,000 patients and a cost of $1,416 per patient; and (3) spiral CT +/- leg ultrasound, with an expected survival of 958.2 per 1,000 patients and a cost of $1,751 per patient. The traditional algorithm was then excluded by extended dominance. The cost per additional life saved was $70,833 for spiral CT +/- leg ultrasound relative to V/Q +/- leg ultrasound +/- spiral CT. CONCLUSIONS: Spiral CT can replace pulmonary angiography in patients with nondiagnostic V/Q scan and negative leg ultrasound findings. This approach is likely as effective as-and possibly less expensive than-the current algorithm for diagnosis of acute PE. When spiral CT is the initial diagnostic test, followed by leg ultrasound, expected survival improves but costs are also considerably higher. These findings were robust to variations in the assumed sensitivity and specificity of spiral CT.     

肺隔离症CTA所见一例报道

目的 探讨计算机体层摄影术(computerized tomography,CT)增强、计算机体层摄影血管造影术(computerized tomography aorta,CTA)诊断肺隔离症的应用价值.方法 分析本院1例经CTA确诊的肺隔离症患者的临床资料,并结合文献进行复习.结果 本院1例患者经CTA证实有异常增粗的迷走血管,明确诊断为肺隔离症.本病诊断的关键是证实来自体循环的异常供血动脉,本文探讨了CT增强、CTA诊断肺隔离症的优势,提供了一种无创的检查方法.结论 CTA检查出异常供血动脉的阳性率高,应成为诊断肺隔离症的首选检查方法.经异常供血动脉栓塞治疗肺隔离症安全,患者痛苦小,并发症少,是一种有效的治疗方法.     

采用160排螺旋扫描模式肺动脉成像技术的临床应用

目的:评价160排螺旋模式肺动脉成像(CTPA)的优势及临床应用价值。方法:70例临床怀疑肺动脉栓塞的受检者,行CTPA检查,按随机表分为2组,A组35例采用160排螺旋模式肺动脉成像;B组35例采用传统64排螺旋模式肺动脉成像。由2名有经验的放射科医师在同一工作站上阅读2组CTPA横断面图像,测量、记录参数包括主肺动脉CT值(CT value of pulmonary artery,PACTv)、主肺动脉CT值标准差(SD)、左心房CT值(CT value of left atrium,LACTv)、主肺动脉CT值与左心房CT值差值(PACTv-LACTv)、延迟时间(delay time,DT)、扫描时间(scan time,ST)、剂量长度乘积(dose length prod-uct,DLP)、有效辐射剂量(effective dose,ED)及对比噪声比(contrast to noise ratio,CRN),并进行统计学分析。结果:2组病例主肺动脉CTv(F=1.499,P=0.079)、主肺动脉SD(F=4.935,P=0.344)差异无统计学意义。而2组病例的左心房CT值(F=1.278,P=0.031)、主肺动脉CT值与左心房CT值差值(F=0.872,P=0.011)、延迟时间(F=1.829,P=0.001)、扫描时间(F=2.373,P=0.000)、对比噪声比(F=2.219,P=0.019)、剂量长度乘积(F=0.032,P=0.000)、有效辐射剂量(F=0.056,P=0.001)及对比剂剂量(F=1.705,P=0.000)差异均有统计学意义。结论:160排螺旋扫描模式CTPA成像的对比噪声比低于传统64排螺旋扫描模式,但160排螺旋扫描模式的扫描时间短,对比剂剂量、有效辐射剂量低,对于急、重症肺动脉栓塞患者临床应用价值更高。     

Sensitivity and specificity of helical computed tomography in the diagnosis of pulmonary embolism: a systematic review

PURPOSE: To determine the sensitivity and specificity of helical computed tomography (CT) for the diagnosis of pulmonary embolism and to determine the safety of withholding anticoagulant therapy in patients who have clinically suspected pulmonary embolism and negative results on helical CT. DATA SOURCES: The MEDLINE database was searched for all reports published from 1986 to October 1999 that evaluated the use of helical CT for the diagnosis of pulmonary embolism. Bibliographies of the retrieved articles were cross-checked to identify additional studies. STUDY SELECTION: All prospective English-language studies were selected. Retrospective studies, review articles, and case reports were excluded, and 5 of the 20 identified articles were excluded. The scientific validity of the remaining 15 articles was assessed. DATA EXTRACTION: Two of the authors used a priori, pre-defined criteria to independently assess each study. A third author resolved disagreements by adjudication. The pre-defined criteria were inclusion of a consecutive series of all patients with suspected pulmonary embolism, inclusion of patients with and those without pulmonary embolism, a broad spectrum of patient characteristics, performance of helical CT and pulmonary angiography (or an appropriate reference test) in all patients, and independent interpretation of the CT scan and pulmonary angiogram (or reference test). Specific data on sensitivity and specificity and the associated 95% CIs were recorded when available. DATA SYNTHESIS: No study met all of the predefined criteria for adequately evaluating sensitivity and specificity. The reported sensitivity of helical CT ranged from 53% to 100%, and specificity ranged from 81% to 100%. In no prospective study was anticoagulant therapy withheld without further testing for venous thromboembolism in consecutive patients with suspected pulmonary embolism. One prospective study reported the outcome of selected patients with negative results on helical CT who did not receive anticoagulant therapy. CONCLUSIONS: Use of helical CT in the diagnosis of pulmonary embolism has not been adequately evaluated. The safety of withholding anticoagulant treatment in patients with negative results on helical CT is uncertain. Definitive large, prospective studies should be done to evaluate the sensitivity, specificity, and safety of helical CT for diagnosis of suspected pulmonary embolism.     

原发性肺动脉肉瘤1例并文献复习

目的 提高对原发性肺动脉肉瘤的认识和诊断水平。方法 结合我院1例经手术病理证实的原发性肺动脉肉瘤患者的临床资料与国内外有关文献,对原发性肺动脉肉瘤的临床表现、影像学表现、实验室检查结果进行分析。结果 原发性肺动脉肉瘤的临床表现与肺动脉血栓栓塞相似,应用CT肺动脉造影鉴别有一定局限性,正电子发射型计算机断层扫描与CT合用有助于诊断。结论 原发性肺动脉肉瘤临床表现及常规影像特异性较少,正电子发射型计算机断层扫描与CT结合有更大的诊断价值。     

肺部孤立性结节的评估及诊断策略的选择

随着胸部CT的广泛应用,肺部孤立性结节的发现率越来越高.如何确认发现的肺部孤立性结节的性质成为临床上亟待解决的问题.少数结节的性质可以通过患者的临床特征及胸部CT特点得到确认,但绝大多数的结节的性质需要通过进一步的检查,包括经验性抗感染治疗、胸部CT定期随访观察、PET/CT检查、纤维支气管镜榆查、CT引导下经胸针吸肺...     

Helical computerized tomography of the thorax in the diagnosis of unresolved chronic pulmonary thromboembolism

We assessed the diagnostic usefulness of helical CT scan of the thorax in the setting of chronic thromboembolic pulmonary hypertension by prospectively comparing the results of helical CT scan to those of the pulmonary angiogram (gold standard). We studied 40 patients with diagnosis of pulmonary hypertension of diverse etiology (mean age: 40.7 +/- 12 y.o.; mean systolic pulmonary artery pressure: 91 +/- 33 mmHg)). Thirty of these patients fulfilled the diagnostic criteria of chronic thromboembolic pulmonary hypertension and the other ten were used as controls. Diagnosis in control patients included: primary pulmonary hypertension (4); patent ductus arteriosus (2); atrial septal defect (1); rheumatic valve disease (1); ischemic heart disease (1); and acute pulmonary embolism (1). Both helical CT scan and pulmonary angiogram were part of the routine diagnostic work up of these patients, and were, performed and interpreted almost simultaneously (within one week) by a different group of investigators in a blind manner. Only the diagnostic accuracy of the method regarding central (major arteries) vascular lesions was evaluated. Helical CT scan had an overall sensitivity of 100% (29/29), and a specificity of 91% (10/11). Positive predictive and negative predictive values were 96.6% (29/30) and 100% (10/10), respectively. Overall diagnostic accuracy was 97.5% (39/40). We conclude that helical CT scan of the thorax is an excellent alternative approach for the diagnosis of major arteries lesions in the setting of chronic thromboembolic pulmonary hypertension.     

A simple diagnostic strategy in hospitalized patients with clinically suspected pulmonary embolism

OBJECTIVES: Diagnostic strategies in patients with suspected pulmonary embolism have been extensively studied in outpatients; their value in hospitalized patients has not been well established. Our aim was to determine the safety and clinical utility of a simple diagnostic strategy in hospitalized patients with suspected pulmonary embolism. DESIGN: Prospective management study. SETTING: Twelve teaching hospitals (five academic, seven general hospitals). SUBJECT: A total of 605 hospitalized patients with clinically suspected pulmonary embolism. All patients completed the study. INTERVENTIONS: First the clinical decision rule (CDR)-score was calculated. An unlikely CDR-score in combination with a normal D-dimer excluded pulmonary embolism. All other patients underwent helical computed tomography (CT). CT either diagnosed or excluded pulmonary embolism, in which case anticoagulants were started or withheld. All patients were instructed to report symptoms of venous thrombosis. Objective tests were performed to confirm venous thromboembolism. The primary outcome was the incidence of symptomatic venous thrombosis during 3-month follow-up. RESULTS: The combination of an unlikely CDR-score and a normal D-dimer excluded pulmonary embolism in 60 patients (10% of all patients); no venous thromboembolic event occurred during follow-up (0%; 95% CI 0-6.7%). CT excluded pulmonary embolism in 380 patients; during follow-up venous thromboembolism occurred in five patients (1.4%; 95% CI 0.4-3.1%). CONCLUSIONS: An unlikely CDR-score in combination with a normal D-dimer appears to exclude pulmonary embolism safely in hospitalized patients. Before clinical implementation it is important this safety is confirmed by others. CT testing was obviated in only 10% of patients. CT can safely exclude pulmonary embolism in hospitalized patients.     

Chronic pulmonary thromboembolism diagnosed on the basis of characteristic mosaic patterns on lung computed tomograms]

We report on a 59-year-old woman who presented with characteristic findings on lung computed tomographic (CT) scans and was therefore suspected to have chronic pulmonary thromboembolism. She visited our hospital because of worsening exertional dyspnea over the preceding year, and because she was dissatisfied with an earlier diagnosis made by another institution. Chest roentgenograms disclosed nonhomogeneous hyperlucency in both lungs associated with linear and bundle shadows, dullness of the right costophrenic angle, and dilatation of the descending branch of the right pulmonary artery. The patient experienced moderate hypoxemia even at rest. Pulmonary function tests demonstrated a restrictive ventilatory pattern associated with reduced diffusion capacity. The lung CT scans disclosed a mosaic pattern of attenuation in the lung parenchyma, which probably reflected scattered areas of low perfusion. The unique characteristics of such CT findings drew our attention to chronic pulmonary thromboembolism as a possible diagnosis. We eventually confirmed the diagnosis on the basis of enhanced CT scans, pulmonary perfusion and ventilation scintigrams, and digital subtraction angiography. In our view, chronic pulmonary thromboembolism should be kept in mind as a possible differential diagnosis of the mosaic patterns of attenuation on lung CT scans.     

Normal perfusion scintigraphy in pulmonary embolism. Causes and diagnostic alternatives

Diagnosing pulmonary embolism (PE) is a challenge for many physicians as it is a frequently occurring disease with nonspecific symptoms and signs. Ventilation-perfusion (V/Q) scintigraphy is widely used as the first step in diagnosing PE since it is non-invasive and highly sensitive. With a normal perfusion scan, clinically relevant pulmonary thrombo-emboli are considered to be absent. In an ongoing study assessing the value of spiral CT in the diagnosis of PE, we encountered a patient who had a normal perfusion scan while a large partially occluding thrombus in the right lower lobe artery and its branches was depicted by spiral CT and pulmonary angiography. In this article, we discuss the significance of normal findings in perfusion scintigraphy, the causes of false-negative perfusion scans and the role of alternative techniques such as spiral CT and pulmonary angiography.     

肺内恶性孤立性小结节的CT征像特征分析与诊断

目的通过对肺内恶性孤立性小结节CT影像特征的分析,不断提高CT对恶性孤立性肺结节的检出率。方法全面、系统地回顾、分析134例肺内孤立性小结节患者的临床资料。结果 134例肺内孤立性小结节患者中,病检恶性80例(59.70%);病检和CT均诊断为恶性者78例,CT与病检符合率为97.5%,病检确诊为恶性而CT征像不支持者2例(2.50%),CT诊断为恶性,而首次病检不支持,再次病检支持者1例(1.25%);81例结节≥2.0 cm者,恶性75例(92.59%);53例结节2 cm者,恶性3例(5.66%);右肺结节恶性率为73.21%,明显高于左肺的43.59%(P0.05);恶性结节CT影像表现中胸膜凹陷征、引流线征、血管集束征、毛刺征、棘突征、分叶征、空泡和细支气管充气征,征像所占比例明显高于良性结节(P0.05);85.90%的恶性结节病例表现为3种以上基本影像征像并存。结论肺内孤立性结节恶性率高,其发病的部位和影像表现均具有其一定的特征性,CT诊断具有较高的检出率,在CT诊断过程中,要紧紧围绕结节的部位和影像征像进行仔细分析鉴别,对一时难以定论的结节要积极开展动态观察,以提高恶性孤立性肺结节的检出率,减少误诊和漏诊。     

Pulmonary endarteritis and subsequent pulmonary embolism associated with clinically silent patent ductus arteriosus

A 49-year-old man without heart murmur was admitted with fever because of bacteremia following a tooth extraction. Antibiotics rapidly alleviated the fever; however, a small nodule in the pulmonary artery was identified on computed tomography (CT). When the patient experienced chest discomfort with fever, CT demonstrated the absence of the nodule and the appearance of an abnormal lung opacity, and echocardiography showed turbulent retrograde flow in the pulmonary artery. We had the rare opportunity to follow a case of pulmonary bacterial endarteritis and subsequent pulmonary embolism with clinically silent patent ductus arteriosus (PDA) that was confirmed by 3-dimensional CT.     

Correlation of CT and pathologic findings of pulmonary lymphangioleiomyomatosis

The X-ray CT findings of two cases of pulmonary lymphangioleiomyomatosis were reported. The correlation between high-resolution CT findings and inflated biopsy specimens was studied. The X-ray CT findings are 1) multiple low attenuation areas, 2) diffuse areas of slightly increased density and 3) irregular enlargement of pulmonary vascular images. Each low attenuation are turned out to correspond to emphysematous lesions. Slightly increased densities on CT images seemed to be caused by a summation of many small nodules of a proliferation of smooth muscle cells located in the wall of respiratory bronchioles and alveolar ducts, with or without intraalveolar hemosiderosis. Some nodular lesions in bronchiolar walls were so close to neighboring vessels that they could not be separated from vascular images on CT, so peripheral vascular images were irregularly thickened. X-ray CT reflected more actual pathological findings than routine chest radiographs. As low attenuation areas on CT images have been reported to be representative of pulmonary emphysema, it is thought that the above CT findings must be differentiated from those of pulmonary emphysema. While pulmonary vascular images were thin and stretched on the CT in patients with emphysema, they were irregularly thickened on the CT of patients with LAM. Furthermore, while CT of emphysema often revealed overinflation or decreased density, diffuse areas of slightly increased density were never found in emphysema.