Pulmonary embolism: computer-aided detection at multidetector row spiral computed tomography

BACKGROUND: We aimed to evaluate the feasibility and performance of a computer-aided detection (CAD) tool for automated detection of segmental and subsegmental pulmonary emboli. METHODS: A CAD tool (ImageChecker CT, R2 Technology, Inc) for automated detection of pulmonary emboli was evaluated on multidetector-row CT studies of varying diagnostic quality in 23 patients (13 female, mean age 52 y) with pulmonary embolism (PE) and of 13 patients (all female, mean age 49 y) without PE. A collimation of 16 x 1 mm and a reconstructed section width of 1.25 mm had been used in each patient. The performance of the CAD tool for the detection of emboli in the segmental and subsegmental pulmonary arterial tree was assessed. Consensus reading of the same studies by 2 radiologists, with a third for adjudication, for the identification of segmental and subsegmental pulmonary emboli was used as the standard of reference. RESULTS: Consensus reading revealed 130 segmental pulmonary emboli and 107 subsegmental pulmonary emboli in the 23 patients with PE. All 23 patients with PE were correctly identified as having PE by the CAD system. In a vessel-by-vessel analysis, the sensitivity of the CAD algorithm was 92% (119/130) for the detection of segmental pulmonary emboli and 90% (92/107) for subsegmental pulmonary emboli. The overall specificity, positive predictive value (95% confidence interval) and negative predictive value (95% confidence interval) of the algorithm were 89.9%, 63.2% (57.9%-68.2%) and 97.7% (96.7%-98.4%), respectively. The average false positive rate of the CAD algorithm was 4.8 (range 1 to 9) false positive detection marks per case. CONCLUSION: CAD of segmental and subsegmental pulmonary emboli based on 1-mm multidetector-row CT studies is feasible. Application of CAD tools may improve the diagnostic accuracy and decrease the interpretation time of computed tomographic angiography for the detection of pulmonary emboli in the peripheral arterial tree and further enhance the acceptance of this test as the first line diagnostic modality for suspected PE.     

Diagnosis of subsegmental pulmonary emboli: a multi-center study using a porcine model

We measured sensitivity, positive predictive value, and free-response receiver operating characteristic (FROC) of 20 radiologists detecting subsegmental-sized pulmonary emboli in a porcine model using either contrast-enhanced computed tomography (CT) or digital subtraction (DS) pulmonary angiography. Colored methacrylate beads (4.2 and 3.8 mm diameter) were injected into 9 anesthetized juvenile pigs. CT and DS pulmonary angiography images were obtained before and after a pulmonary infiltrate was introduced into the lower lobes. Following imaging, the pigs were euthanized, and the pulmonary arterial tree was cast using clear methacrylate allowing direct visualization of emboli. The 20 radiologists used a custom-made computer application to display the images on their personal computer and record their diagnoses. The results were mailed electronically to the coordinating center for comparison with the cast of the pulmonary vasculature. Twenty-three emboli were included in the statistical analysis. Overall sensitivity for spiral CT and angiography, respectively, was: 60 +/- 18% and 72 +/- 11% (P = 0.06). Positive predictive value for spiral CT and angiography, respectively, was: 49 +/- 24% and 58 +/- 23% (P = 0.25). There was a large variation in both sensitivity and positive predicted values between Readers. There was no difference in sensitivity or positive predictive value between radiologists from community or academic centers (P > 0.27). FROC analysis showed no significant difference between CT or DS (P = 0.27). In conclusion, in this porcine model, there is no overall diagnostic advantage to using DS pulmonary angiography rather than contrast-enhanced spiral CT for the diagnosis of PE when images are interpreted by radiologists located in either academic or community hospital settings.     

Computer-aided diagnosis as a second reader: spectrum of findings in CT studies of the chest interpreted as normal

STUDY OBJECTIVES: To assess the performance of an automated computer-aided detection (CAD) system as a second reader on chest CT studies interpreted as normal at routine clinical interpretation. DESIGN: Chest CT studies were processed using a prototype CAD system for automated detection of lung lesions. Three experienced radiologists analyzed each CAD finding and confirmed or dismissed the marked image features as lung lesions. Noncalcified, focal lung lesions were classified according to size as being of high (> or = 10 mm), intermediate (5 to 9 mm), or low (< or = 4 mm) significance. SETTING: Two sub-specialized academic tertiary referral centers in the United States and Germany. PATIENTS: Chest CT studies were performed in 100 patients, with results initially reported as normal at clinical double reading. Indications for chest CT were suspected pulmonary embolism (PE) [n = 33], lung cancer screening in a high-risk population (n = 28), or follow-up for a cancer history (n = 39). INTERVENTIONS: Reevaluation of all chest CT studies for focal lung lesions with the CAD system as a second reader. MEASUREMENTS: Prevalence and spectrum of lung lesions missed at routine clinical interpretation but found by the CAD system. RESULTS: In 33% (33 of 100 patients), CAD detected significant lung lesions that were not previously reported. Fifty-three significant lesions were detected (mean, 1.6 lesions per case), of which 5 lesions (9.4%) were of high significance, 21 lesions (39.6%) were of intermediate significance, and 27 lesions (50.9%) were of low significance. In the PE group, the lung cancer screening group, and the group with a cancer history, four patients (12.1%), six patients (21.4%), and nine patients (23.1%), respectively, had focal lung lesions of high and/or intermediate significance. The false-positive rate of the CAD system was an average of 1.25 per case (range, 0 to 11). CONCLUSIONS: Significant lung lesions are frequently missed at routine clinical interpretation of chest CT studies but may be detected if CAD is used as an additional reader.     

Diagnostic accuracy of three-dimensional contrast-enhanced MR angiography at 3-T for acute pulmonary embolism detection: Comparison with multidetector CT angiography

Background

Three-dimensional contrast-enhanced MR pulmonary angiography (MRPA) is a suitable option for pulmonary embolism (PE) detection. However, there have been few reports on the diagnostic accuracy of MRPA for PE detection in a 3-T MR system. The purpose of this study was to evaluate the accuracy of MRPA in a 3-T MR system to detect acute PE with multidetector CT pulmonary angiography (CTPA) as reference standard.

Methods

Twenty-seven patients (18 males and 9 females, mean age 38.9 ± 14.4 years) underwent both MRPA and CTPA within 3 days (range, 0–3 days) for evaluating PE. Pulmonary emboli in MRPA were independently analyzed on a per-patient and per-lobe basis by two radiologists. CTPA was regarded as reference standard, which was evaluated by another two radiologists in consensus. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for PE detection were calculated. Weighted κ values were calculated to evaluate agreement between readers.

Results

Twenty-four patients had PE in 55 lung lobes in CTPA, while 3 patients had no PE detected. Readers 1 and 2 correctly detected 47 and 46 lung lobes having clots in 24 and 23 patients, corresponding to sensitivities, specificities, PPV, NPV, and accuracies of 100%, 100%, 100%, 100%, 100%; 100%, 66.7%, 96.0%, 100%, 96.4% on a per-patient basis and 85.5%, 100%, 100%, 90.9%, 94.1%; 83.6%, 93.7%, 90.2%, 89.2%, 89.6% on a per-lobe basis; respectively. Excellent inter-reader agreement (κ values = 1.00 and 0.934; both P < 0.001) were found for detecting PE on a per-patient and per-lobe analysis.

Conclusion

Three-dimensional contrast-enhanced MRPA with a 3-T MR system is a suitable alternative modality to CTPA to detect PE on a per-patient basis based on this small cohort study.     

Thoracic ultrasound for diagnosing pulmonary embolism: a prospective multicenter study of 352 patients

BACKGROUND: Pulmonary embolism (PE) continues to be a major challenge in terms of diagnosis, as evidenced by the fact that many patients die undiagnosed and/or untreated. The aim of this multicenter study was to determine the accuracy of thorax ultrasound (TUS) in the diagnosis of PE (TUSPE). METHODS: From January 2002 through September 2003, 352 patients with suspected PE were examined in seven clinics. The patients were investigated prospectively by TUS according to the following criteria: (1) PE confirmed: two or more typical triangular or rounded pleural-based lesions; (2) PE probable: one typical lesion with pleural effusion; (3) PE possible: small (< 5 mm) subpleural lesions or a single pleural effusion alone; or (4) normal TUS findings. In all cases, CT pulmonary angiography (CTPA) was used as the reference method. In the event of discrepant findings, a combination of duplex sonography of the leg veins, echocardiography, ventilation/perfusion scintigraphy, and a quantitative enzyme-linked immunosorbent assay or latex d-dimer, or a biopsy/autopsy was performed.Findings: PE was diagnosed in 194 patients. On TUS, 144 patients had a total of 333 subpleural lesions (mean, 2.3 lesions per patient) averaging 15.5 x 12.4 mm in size. Additionally, a narrow pleural effusion was found in 49% of the patients. TUS yielded the following results under application of the strict criteria 1 and 2: PE true-positive, n = 144; PE false-positive, n = 8; PE true-negative, n = 150; and PE false-negative, n = 50. The sensitivity was 74%, specificity was 95%, positive predictive value was 95%, negative predictive was value 75%, and accuracy was 84%, at a prevalence of 55%. The sensitivity in patients with criterion 1 was 43% and a specificity of 99%.Interpretation: TUS is a noninvasive method to diagnose peripheral PE. In the absence of CTPA, TUS is a suitable tool to demonstrate a PE at the bedside and in the emergency setting.     

Sonography of lung and pleura in pulmonary embolism: sonomorphologic characterization and comparison with spiral CT scanning.

STUDY OBJECTIVES: Despite the widespread use of lung scanning and angiography, pulmonary embolisms (PEs) remain undiagnosed in the majority of patients, suggesting the need for alternative diagnostic approaches. The present study investigates the clinical utility of transthoracic sonography (TS) for the diagnosis of PE and compares the data obtained with the technique to those obtained by spiral CT (sCT) scanning. DESIGN: This prospective study was performed using 69 patients with suspected PEs. TS was performed in all patients. In addition, sCT scanning was carried out in 62 patients. Other diagnostic procedures included the estimation of d-dimers, echocardiography, venous duplex sonography of the legs, pulmonary angiography, and ventilation/perfusion scanning. The diagnosis of PE was accepted when there was a conclusive result of these investigations or when an embolus could be visualized on a CT scan. SETTING: The Department of Pneumology in Friedrich-Schiller-University Hospital (Jena, Germany). PATIENTS: Sixty-nine patients (27 women and 42 men) with suspected PEs. RESULTS: A diagnosis of PE was established in 44 patients. Ninety-one peripheral parenchymal lesions (mean, 2.6 lesions per patient; range 1 to 9 lesions per patient) that are associated with PE were detected by TS in 35 patients (80%). Multiple, triangular, hypoechoic, and pleural-based parenchymal lesions with a localized and/or basal effusion were typical of the PEs as shown by TS. In nine patients with central PEs that had been diagnosed by CT scanning, no peripheral lesions could be detected by sonography. One patient with sonographic signs of PEs had a diffuse bronchogenic adenocarcinoma that was diagnosed at autopsy. In another patient with parenchymal lesions, pneumonia was diagnosed by CT scanning. The sensitivity of TS for detecting PEs was 80% (sensitivity of CT scanning, 82%), and the specificity of TS for detecting pulmonary lesions was 92% (specificity of CT scanning, 100%). The positive and negative predictive values of TS for the detection of PEs were 95% and 72%, respectively (positive predictive value for CT scanning, 100%; negative predictive value for CT scanning, 77%). The accuracy of TS was 84% (accuracy of CT scanning, 89%). CONCLUSIONS: TS is a noninvasive technique that is used for diagnosing parenchymal alterations, and it may serve as an additional method in the strategy for diagnosing PE.     

Non-invasive exclusion and diagnosis of pulmonary embolism by sequential use of the rapid ELISA D-dimer assay, clinical score and spiral CT.

Pulmonary angiography is the gold standard for segmental pulmonary embolism (PE) but no longer for its subsegmental PE, because the inter-observer agreement for angiographically documented subsegmental PE is only 60%. Two non-invasive tools exclude PE with a negative predictive value of > 99%: a normal perfusion lung scan and a normal rapid ELISA VIDAS D-dimer test. The positive predictive value of a high probability ventilation-perfusion lung scan (VP-scan) is only 85% to 87%. The combination of a low clinical score and a non-diagnostic VP-scan safely exclude PE without the need of angiography. The prevalence of PE and that of an alternative diagnosis in symptomatic patients with a non-diagnostic VP-scan are 10% to 20% and 30% to 45%, respectively. Helical spiral computed tomography (CT) detects all clinically relevant PE and a large number of alternative diagnoses in symptomatic patients with a non-diagnostic or high probability VP-scan. The positive predictive value of the spiral CT is > 95%. Single-slice helical CT as the primary diagnostic test in patients with suspected PE in retrospective outcome studies and in prospective multicenter management studies indicate that the negative predictive value of a negative spiral CT preceded or followed by a negative compression ultrasonography (CUS) is > 99%. Therefore, a helical spiral CT can replace both the VP-scan and pulmonary angiography to safely rule in and out PE. A negative rapid ELISA VIDAS D-dimer test result will reduce the need for helical spiral CT by 25% to 35%.     

Diagnostic value of CT angiography in coronary arteries stenosis detection

BACKGROUND: Noninvasive imaging of coronary arteries is very important. CT angiography (multislice computed tomography and electron beam computed tomography -- MSCT and EBT) is most reliable method for noninvasive coronary visualization. PURPOSE: The aim of our study was to evaluate the diagnostic value of CT angiography in coronary arteries stenoses detection in patients with coronary arteries disease (CAD). MATERIALS AND METHODS: 140 patients with CAD who underwent EBT (n=97) or 4-slice CT (n=43) coronary angiography and conventional coronary angiography as a gold standard were included in the study. RESULTS: Sensitivity and specificity of CT angiography in coronary stenoses detection (proximal and mid segments) were 86% and 97%, respectively. Positive and negative predictive values were 90% and 96%, respectively. Overall accuracy was 95%. 6.2% of coronary segments were excluded from the study because of unsatisfactory image quality. CONCLUSIONS: CT angiography is noninvasive method for coronary stenoses detection with high sensitivity and specificity. Nevertheless EBT and 4-slice CT angiography can not replace conventional coronary angiography because of lower temporal and spatial resolution, artifacts in patients with arrhythmias and huge coronary calcification.     

Non-invasive coronary computed tomographic angiography for patients with suspected coronary artery disease: the Coronary Angiography by Computed Tomography with the Use of a Submillimeter resolution (CACTUS) trial.

BACKGROUND: Non-invasive coronary angiography by multislice spiral computed tomography (MSCT) is a promising method for the diagnosis of coronary artery disease (CAD). However, the clinical role of this method has not been established for specific patient cohorts. Therefore, the objective of the current prospective, blinded study was to investigate the diagnostic value of coronary MSCT angiography in patients with an intermediate pre-test probability for having CAD when compared with invasive angiography. METHODS AND RESULTS: A total of 243 patients with an intermediate pre-test probability for having CAD were asked to undergo coronary 16- or 64-slice CT angiography before planned invasive angiography from 12 September 2003 to 13 July 2005. The primary end point was defined as the diagnostic accuracy in the detection of significant coronary stenosis (> or =50% lumen diameter reduction) on a per-patient and an 'intention-to-diagnose'-based analysis. Secondary end points comprised per-artery and per segment-based analyses as well as the comparison of diagnostic accuracy of 16- vs. 64-slice MSCT angiography. Of 243 enrolled patients, 129 and 114 patients were studied by 16- and 64-slice CT angiography, respectively. The overall sensitivity, negative predictive value, and specificity for CAD detection by MSCT were 99% (95% CI, 94-99%), 99% (95% CI, 94-99%), and 75% (95% CI, 67-82%), respectively. On a per-segment basis, the use of 64-slice CT was associated with significantly less inconclusive segments (7.4 vs. 11.3%, P < 0.01), resulting in a trend to an improved specificity (92 vs. 88%, P = 0.09). CONCLUSION: In patients with an intermediate pre-test probability for having CAD this large, prospective trial demonstrates that non-invasive coronary CT angiography is a very sensitive method for CAD detection. Furthermore, this method allows ruling out CAD very reliably and safely. Finally, 64-slice CT appears to be superior for CAD detection when compared with 16-slice CT.     

Performance of helical computed tomography in unselected outpatients with suspected pulmonary embolism.

BACKGROUND: Helical computed tomography (CT) is commonly used to diagnose pulmonary embolism, although its operating characteristics have been insufficiently evaluated. OBJECTIVE: To assess the sensitivity and specificity of helical CT in suspected pulmonary embolism. DESIGN: Observational study. SETTING: Emergency department of a teaching and community hospital. PATIENTS: 299 patients with clinically suspected pulmonary embolism and a plasma D -dimer level greater than 500 microgram/L. INTERVENTION: Pulmonary embolism was established by using a validated algorithm that included clinical assessment, lower-limb compression ultrasonography, lung scanning, and pulmonary angiography. MEASUREMENTS: Sensitivity, specificity, and likelihood ratios of helical CT and interobserver agreement. Helical CT scans were withheld from clinicians and were read 3 months after acquisition by radiologists blinded to all clinical data. RESULTS: 118 patients (39%) had pulmonary embolism. In 12 patients (4%), 2 of whom had pulmonary embolism, results of helical CT were inconclusive. For patients with conclusive results, sensitivity of helical CT was 70% (95% CI, 62% to 78%) and specificity was 91% (CI, 86% to 95%). Interobserver agreement was high (kappa = 0.823 to 0.902). The false-negative rate was lower for helical CT used after initial negative results on ultrasonography than for helical CT alone (21% vs. 30%). Use of helical CT after normal results on initial ultrasonography and nondiagnostic results on lung scanning had a false-negative rate of only 5% and a false-positive rate of only 7%. CONCLUSION: Helical CT should not be used alone for suspected pulmonary embolism but could replace angiography in combined strategies that include ultrasonography and lung scanning.     

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.     

Virtual colonoscopy compared with conventional colonoscopy for stricturing postoperative recurrence in Crohn's disease

BACKGROUND: The place of virtual colonoscopy (VC) in patients with Crohn's disease (CD) requiring endoscopic follow-up after surgery is unknown. The authors compared findings from VC versus conventional colonoscopy (CC) for assessing the postoperative recurrence of CD. METHODS: Sixteen patients with ileocolonic anastomosis for CD were prospectively enrolled from January 2001 to January 2002. Recurrence was assessed by CC according to Rutgeerts et al. VC was performed with a computed tomography scanner, with images examined by three radiologists who were unaware of the endoscopic findings. RESULTS: CC showed perianastomotic recurrence in 15 of 16 patients. Perianastomotic narrowing or stenosis was detected by VC in 11 of these 15 patients. There were 11 true positive, 1 true negative, 0 false-positive, and 4 false-negative findings (73% sensitivity, 100% specificity, 100% positive predictive value, 20% negative predictive value, 75% accuracy). Among the eight patients showing a rigid stenosis of the anastomosis not allowing passage of the colonoscope, VC detected narrowing or stenosis in seven patients. CONCLUSIONS: The current findings suggest that although the widespread use of VC in CD is currently not indicated because of possible false-negative findings, this technique may represent an alternative to CC in noncompliant postsurgical patients with a rigid stenosis not allowing passage of the endoscope.     

Quantitative d-dimer levels and the extent of venous thromboembolism in CT angiography and lower limb ultrasonography

BACKGROUND: We evaluated the diagnostic yield of multidetector-row CT angiography and determined the clot burden within pulmonary vasculature as a measure of pulmonary embolism (PE) severity at different d-dimer levels and pretest clinical probabilities. PATIENTS AND METHODS: 254 consecutive patients referred to CT pulmonary angiography for suspected PE after d-dimer testing were grouped into clinical probability classes using Wells' score, and the frequency of PE was determined. A score representing clot burden within pulmonary vasculature was calculated from the number of obstructed segmental arteries in CT scans in a partly differing group of 96 PE positive patients. RESULTS: The prevalence of PE increases with the d-dimer level (7% at d-dimer levels of 0.5-1 microg/ml, reaching 90% at d-dimer levels > 9 microg/ml; p < 0.001). D-dimer levels above 4 microg/ml are associated with a significantly higher clot burden in pulmonary arteries (median score 11 versus 5, and 53% versus 16% of patients in the subgroup with a score > 10 points; p < 0.001), and thrombus in a main pulmonary artery was detected more frequently (37% versus 9%, p = 0.003). Similar results were obtained for distal versus proximal deep venous thromboses, detected by ultrasonography of the lower limb in a separate group of 44 patients. CONCLUSIONS: High d-dimer levels are associated with an increased prevalence of CT radiographic findings indicating extended clinically severe PE or lower limb venous thrombosis.     

Identification of chronic thromboembolic pulmonary hypertension on CTPAs performed for diagnosing acute pulmonary embolism depending on level of expertise

BackgroundExpert reading often reveals radiological signs of chronic thromboembolic pulmonary hypertension (CTEPH) or chronic PE on computed tomography pulmonary angiography (CTPA) performed at the time of acute pulmonary embolism (PE) presentation preceding CTEPH. Little is known about the accuracy and reproducibility of CTPA reading by radiologists in training in this setting.ObjectivesTo evaluate 1) whether signs of CTEPH or chronic PE are routinely reported on CTPA for suspected PE; and 2) whether CTEPH-non-expert readers achieve comparable predictive accuracy to CTEPH-expert radiologists after dedicated instruction.MethodsOriginal reports of CTPAs demonstrating acute PE in 50 patients whom ultimately developed CTEPH, and those of 50 PE who did not, were screened for documented signs of CTEPH. All scans were re-assessed by three CTEPH-expert readers and two CTEPH-non-expert readers (blinded and independently) for predefined signs and overall presence of CTEPH.ResultsSigns of chronic PE were mentioned in the original reports of 14/50 cases (28%), while CTEPH-expert radiologists had recognized 44/50 (88%). Using a standardized definition (≥3 predefined radiological signs), moderate-to-good agreement was reached between CTEPH-non-expert readers and the experts’ consensus (k-statistics 0.46; 0.61) at slightly lower sensitivities. The CTEPH-non-expert readers had moderate agreement on the presence of CTEPH (κ-statistic 0.38), but both correctly identified most cases (80% and 88%, respectively).ConclusionsConcomitant signs of CTEPH were poorly documented in daily practice, while most CTEPH patients were identified by CTEPH-non-expert readers after dedicated instruction. These findings underline the feasibility of achieving earlier CTEPH diagnosis by assessing CTPAs more attentively.     

Computer-aided detection (CAD) in lung cancer screening at chest MDCT: ROC analysis of CAD versus radiologist performance

To evaluate the performance of a computer-aided detection (CAD) algorithm in the detection of pulmonary nodules on high-resolution multidetector row computed tomography images in a large, homogeneous screening population, and to evaluate the effect of the system output on the performance of radiologists, using receiver operating characteristic analysis. Three radiologists with variable experience (1 to 7 y), independently read the 200 computed tomography scans and assigned each nodule candidate a confidence score (1-2-3: unlikely, probably, and definitely a nodule). CAD was applied to all scans; successively readers reevaluated all findings of the CAD, assigning, in consensus, a confidence score (1 to 3). The reference standard was established by the consensus of 2 experienced radiologists with 30 and 15 years of experience. Results were used to generate an free-response receiver operating characteristic analysis. The reference standard showed 125 nodules. Sensitivity for readers I-II-III was 57%, 68%, and 46%. A double reading resulted in an increase in sensitivity up to 75%. With CAD, sensitivity was increased to 94%, 96%, and 94% for readers I, II, and III. The area under the free-response receiver operating characteristic curve (Az) was 0.72, 0.82, 0.55, and 0.84 for readers I, II, III, and the CAD, when considering all nodules. Differences between readers I-II and CAD were not significant (P=0.9). There was a significant difference between reader III and the CAD. For nodules <6-mm Az was 0.40, 0.47, 0.14, and 0.72 for readers I, II, III, and the CAD. Differences between all readers and the CAD were significant (P<0.05). CAD can aid in daily radiologic routine detecting a substantial number of nodules unseen by radiologists. This is true for both board-certified radiologists and for less experienced readers especially in the detection of small nodules.     

Impact of spiral computed tomography on the diagnosis of pulmonary embolism in a community hospital setting

BACKGROUND: While the optimal role of spiral CT angiography (CTA) in the diagnosis of pulmonary embolism (PE) remains controversial, this technology is already being widely utilized in the community setting. OBJECTIVES: To assess the impact CTA has had on angiography utilization rates and the overall diagnostic rate of PE. METHODS: All patients evaluated for PE during a 4-year period were studied. PE was defined as either a high-probability V/Q scan, a positive conventional angiogram, or a CTA with emboli in the segmental or larger pulmonary vessels. Diagnostic rates of PE per 1,000 hospital admissions were determined and analyzed for time periods before and after the introduction of CTA. CT reports were compared with their concurrent chest radiograph (CXR) reports and additional findings that were not apparent on CXR were abstracted. RESULTS: The diagnostic rate of PE per 1,000 hospital admissions was 1.8 prior to the introduction of CTA and increased to 2.8 per 1,000 admissions after the introduction of CTA (p < 0.0001). Total costs for diagnostic testing per PE diagnosis made went from US 2,518 dollars to US 2,572 dollars. While the number of PE diagnosed by V/Q scan remained constant, the number of PE diagnosed by conventional angiography decreased while the number diagnosed by CTA increased. In patients with intermediate probability V/Q scan results, the percentage of patients receiving subsequent angiography (conventional or CTA) increased from 17 to 26% (p = 0.043). When conventional angiography was performed, CT imaging of the chest still had to be ordered for other reasons 38% of the time. Additional information was obtained in 78% of cases when CTA was performed. CONCLUSIONS: Increased utilization of CTA was associated with an increase in angiography utilization rates and diagnostic rates of PE, was cost effective, and often provided additional, useful, and unanticipated diagnostic information.     

A negative SimpliRED D-dimer assay result does not exclude the diagnosis of deep vein thrombosis or pulmonary embolus in emergency department patients

STUDY OBJECTIVE: To determine whether a negative SimpliRED D-dimer assay result excludes the diagnosis of deep vein thrombosis (DVT) or pulmonary embolus (PE) in emergency department patients. METHODS: This prospective, institutional review board-approved, clinical trial enrolled consecutive adult ED patients with the suspected diagnosis of venous thromboembolism (VTE) (DVT or PE). Initial ED evaluation included the SimpliRED D-dimer assay (American Diagnostica Inc, Greenwich, CT). Physicians were blinded to assay results. The diagnosis of DVT was made with positive findings on lower-extremity ultrasonography. PE was confirmed by a high-probability ventilation/perfusion (V/Q) scan, a positive pulmonary angiogram, or a positive finding on lower-extremity ultrasonography. A presumptive diagnosis of VTE was made in patients who had VTE at follow-up or unexplained death during the study period. RESULTS: One hundred ninety-eight patients were enrolled during the study period. Twenty-five patients were excluded from data analysis; 9 had no diagnostic testing and 16 were lost to follow-up. Of the 173 patients analyzed, 57 (33%) had VTE-16 of 48 evaluated for DVT and 41 of 125 for suspected PE. The SimpliRED assay had a sensitivity of 65% and a negative predictive value of 81% for detection of VTE. In patients evaluated for DVT alone, the sensitivity was 56% and the negative predictive value was 77%. For patients with suspected PE, the sensitivity and negative predictive value were 68% and 83%, respectively. CONCLUSION: In contrast to earlier reports on the SimpliRED D-dimer assay, a negative result failed to exclude the diagnosis of VTE in our ED population.     

老年肺栓塞的螺旋CT肺动脉造影诊断研究

目的探讨螺旋CT肺动脉造影在老年肺动脉栓塞(PE)诊断中的临床应用价值。方法采用螺旋CT对66例老年PE患者行肺动脉增强扫描,其中多层、单层螺旋CT(MSCT,SCT)肺动脉造影检查者各为21和45例。结果分析66例老年PE患者的2728支肺动脉,MSCT、SCT肺动脉造影共显示926支肺动脉受累。直接征象为中心型充盈缺损、部分型充盈缺损、完全性阻塞、附壁性充盈缺损,约占33.9%;1206支段以上肺动脉中,依据直接征象MSCT、SCT分别检出240支/384支(62.5%)和481支/822支(58.5%),共721支/1206支,两者检出率无明显差别(P=0.037);1522支亚段肺动脉中,MSCT、SCT分别检出121支/484支(25.0%)和84支/1038支(8.1%),共205支/1522支,前者检出率明显高于后者(P=0.632)。平扫示间接征象共125例次。结论MSCT、SCT对段以上PE的诊断二者均有较高的准确度,MSCT对亚段PE的诊断有其优势。     

64排螺旋CT冠脉成像与冠脉造影对冠心病诊断的比较

目的：探讨64排螺旋CT冠脉成像对冠心病的诊断价值。方法：以冠脉造影（CAG）结果为金指标，采用64排螺旋CT对100例疑诊冠心病患者的冠脉主干及主要分支400节段进行重建和分析，评价其诊断冠心病的灵敏性和特异性。结果：64排螺旋CT能清晰显示冠脉主干及分支狭窄、钙化、开口起源异常及桥血管病变，对冠脉狭窄性病变的诊断准确性高，诊断冠脉病变的灵敏度96.37％，特异度96．14％，阳性预测值95．88％，阴性预测值96．6％。但对慢性闭塞性病变诊断性的准确率稍差，灵敏度50％，特异度96．77％，阳性预测值62．5％，阴性预测值94．73％。结论：64排螺旋CT冠脉成像对冠脉狭窄病变、桥血管、心肌桥、支架管腔均显影良好，对钙化病变诊断率优于冠脉造影，可以作为冠心病高危人群无创性筛选检查及冠脉支架、搭桥术后随访手段。     

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.