Lawrence R. Goodman

Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: A Multicenter Prospective Study (PIOPED III)

BACKGROUND The accuracy of gadolinium-enhanced magnetic resonance pulmonary angiography and magnetic resonance venography for diagnosing pulmonary embolism has not been determined conclusively. OBJECTIVE To investigate performance characteristics of magnetic resonance angiography, with or without magnetic resonance venography, for diagnosing pulmonary embolism. DESIGN Prospective, multicenter study from 10 April 2006 to 30 September 2008. SETTING 7 hospitals and their emergency services. PATIENTS 371 adults with diagnosed or excluded pulmonary embolism. MEASUREMENTS Sensitivity, specificity, and likelihood ratios were measured by comparing independently read magnetic resonance imaging with the reference standard for diagnosing pulmonary embolism. Reference standard diagnosis or exclusion was made by using various tests, including computed tomographic angiography and venography, ventilation-perfusion lung scan, venous ultrasonography, d-dimer assay, and clinical assessment. RESULTS Magnetic resonance angiography, averaged across centers, was technically inadequate in 25% of patients (92 of 371). The proportion of technically inadequate images ranged from 11% to 52% at various centers. Including patients with technically inadequate images, magnetic resonance angiography identified 57% (59 of 104) with pulmonary embolism. Technically adequate magnetic resonance angiography had a sensitivity of 78% and a specificity of 99%. Technically adequate magnetic resonance angiography and venography had a sensitivity of 92% and a specificity of 96%, but 52% of patients (194 of 370) had technically inadequate results. LIMITATION A high proportion of patients with suspected embolism was not eligible or declined to participate. CONCLUSION Magnetic resonance pulmonary angiography should be considered only at centers that routinely perform it well and only for patients for whom standard tests are contraindicated. Magnetic resonance pulmonary angiography and magnetic resonance venography combined have a higher sensitivity than magnetic resonance pulmonary angiography alone in patients with technically adequate images, but it is more difficult to obtain technically adequate images with the 2 procedures.

Acute pulmonary embolism: sensitivity and specificity of ventilation-perfusion scintigraphy in PIOPED II study.

PURPOSE To use Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II data to retrospectively determine sensitivity and specificity of ventilation-perfusion (V/Q) scintigraphic studies categorized as pulmonary embolism (PE) present or PE absent and the proportion of patients for whom these categories applied. MATERIALS AND METHODS The PIOPED II study had institutional review board approval at all participating centers. Patient informed consent was obtained; the study was HIPAA compliant. Approval and consent included those for future retrospective research. Patients in the PIOPED II database of clinical and imaging results were included if they had diagnosis at computed tomographic (CT) angiography, Wells score, and diagnosis at V/Q scanning. V/Q scan central readings were recategorized as PE present (PIOPED II reading = high probability of PE), PE absent (PIOPED II reading = very low probability of PE or normal), or nondiagnostic (PIOPED II reading = low or intermediate probability of PE). A composite reference standard was used: the PIOPED II digital subtraction angiographic (DSA) result, or if there was no definitive DSA result, CT angiographic results that were concordant with the Wells score (ie, positive CT angiographic result and Wells score > 2 or negative CT angiographic result and Wells score < 6). Sensitivity and specificity of recategorized central readings were computed. RESULTS With the exclusion of patients with intermediate or low probability, the sensitivity of a high probability (PE present) scan finding was 77.4% (95% confidence interval [CI]: 69.7%, 85.0%), while the specificity of very low probability or normal (PE absent) scan finding was 97.7% (95% CI: 96.4%, 98.9%). The percentage of patients with a PE present or PE absent scan finding was 73.5% (95% CI: 70.7%, 76.4%). CONCLUSION In a population similar to that in PIOPED II, results of V/Q scintigraphy can be diagnostically definitive in a majority of patients; thus, it can be considered an appropriate pulmonary imaging procedure in patients for whom CT angiography may be disadvantageous.

Inherent Variability of CT Lung Nodule Measurements In Vivo Using Semiautomated Volumetric Measurements

OBJECTIVE The objective of our study was to evaluate repeatability and reproducibility of lung nodule volume measurements using volumetric nodule-sizing software. MATERIALS AND METHODS Fifty nodules, less than 20 mm in diameter, in 29 patients were scanned with 1.25-mm collimation using MDCT (time 1 = T1). During the same session, two additional scans, using identical technique, were obtained through each nodule (T2, T3). Three observers working independently then obtained volumetric measurements using a semiautomated volumetric nodule-sizing software package. Qualitative nodule characterization was also performed. The Bland-Altman method for assessing measurement agreement was used to calculate the 95% limits for agreement for nodule volumes at T1, T2, and T3. RESULTS Automated nodule segmentation was successful in 438 (97%) of 450 measurements. Forty-three nodules were available for final evaluation. Twenty-six nodules had well-defined edges, and 17 had irregular or spiculated margins. Seventeen were freestanding, 16 were juxtapleural, and 10 were juxtavascular in location. Average nodule volume was 345.5 mm(3) (range, 49.3-1,434 mm(3)). The mean interobserver variability (repeatability) was 0.018% (SD = 0.73%), and the SD of the mean for the three contemporaneous scans (reproducibility) was 13.1% (confidence limits, +/- 25.6%). SD and confidence limits narrowed as volumes increased. CONCLUSION Volumetric measurements show minimal interobserver variability (0.018%) but an interscan SEM of 13.1% (confidence limits, +/- 25.6%). Repeatability and reproducibility of volumetric measurements are better than those of linear measurements reported in the literature.

CT Venography and Compression Sonography Are Diagnostically Equivalent: Data from PIOPED II

OBJECTIVE The purpose of this study was to compare the clinical value of CT venography (CTV) after MDCT angiography (CTA) with venous compression sonography for the diagnosis of venous thromboembolism (VTE). The Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) showed that lower extremity imaging detects about 7% more patients requiring anticoagulation than CTA alone. SUBJECTS AND METHODS PIOPED II was a prospective multicenter study investigating the accuracy of CTA alone and CTA and CTV together. A composite reference standard was used to confirm, or rule out, pulmonary embolus. Adequate quality CTV and sonographic images were obtained in 711 patients. RESULTS There was 95.5% concordance between CTV and sonography for the diagnosis or exclusion of deep venous thrombosis (DVT); the kappa statistic was 0.809. The sensitivity and specificity of combined CTA and CTV were equivalent to those of combined CTA and sonography. Diagnostic results in subgroups, including patients with signs or symptoms of DVT, asymptomatic patients, and patients with a history of DVT, were similar whether CTV or sonography was used. Patients with signs or symptoms of DVT were eight times more likely to have DVT, and patients with a history of DVT were twice as likely to have positive findings. CONCLUSION CTV and sonography showed similar results in diagnosing or excluding DVT. The incidence of positive studies in patients without signs, symptoms, or history of DVT is low. In terms of clinical significance, CT venography and lower extremity sonography yield equivalent diagnostic results; the incidence of positive studies in patients without signs, symptoms, or history of DVT is low; thus the choice of imaging technique can be made on the basis of safety, expense, and time constraints.

Enlarged Right Ventricle Without Shock in Acute Pulmonary Embolism: Prognosis

OBJECTIVE An unsettled issue is the use of thrombolytic agents in patients with acute pulmonary embolism (PE) who are hemodynamically stable but have right ventricular (RV) enlargement. We assessed the in-hospital mortality of hemodynamically stable patients with PE and RV enlargement. METHODS Patients were enrolled in the Prospective Investigation of Pulmonary Embolism Diagnosis II. Exclusions included shock, critical illness, ventilatory support, or myocardial infarction within 1 month, and ventricular tachycardia or ventricular fibrillation within 24 hours. We evaluated the ratio of the RV minor axis to the left ventricular minor axis measured on transverse images during computed tomographic angiography. RESULTS Among 76 patients with RV enlargement treated with anticoagulants and/or inferior vena cava filters, in-hospital deaths from PE were 0 of 76 (0%) and all-cause mortality was 2 of 76 (2.6%). No septal motion abnormality was observed in 49 patients (64%), septal flattening was observed in 25 patients (33%), and septal deviation was observed in 2 patients (3%). No patients required ventilatory support, vasopressor therapy, rescue thrombolytic therapy, or catheter embolectomy. There were no in-hospital deaths caused by PE. There was no difference in all-cause mortality between patients with and without RV enlargement (relative risk=1.04). CONCLUSION In-hospital prognosis is good in patients with PE and RV enlargement if they are not in shock, acutely ill, or on ventilatory support, or had a recent myocardial infarction or life-threatening arrhythmia. RV enlargement alone in patients with PE, therefore, does not seem to indicate a poor prognosis or the need for thrombolytic therapy.

Diagnosis and Management of Isolated Subsegmental Pulmonary Embolism: Review and Assessment of the Options

We assessed the potential safety of withholding treatment of pulmonary embolism (PE) limited to subsegmental branches. Literature review showed that untreated patients with mostly subsegmental PE had no fatal recurrences in 1 to 3 months and no nonfatal recurrences of PE in 3 months. Patients with suspected PE who had nondiagnostic ventilation/perfusion lung scans, adequate cardiorespiratory reserve or low or moderate clinical probability, and negative serial noninvasive leg tests were shown not to require treatment. It appears safe, therefore, to withhold treatment of subsegmental PE providing (1) pulmonary–respiratory reserve is good; (2) no evidence of deep venous thrombosis (DVT) on serial testing; (3) major risk factor for PE was transient and no longer present; (4) no history of central venous catheterization or atrial fibrillation; and (5) willingness to return for serial venous ultrasound. After fully informing patients, some may choose to be treated and some may choose not to be treated.

Pulmonary Embolism in Pregnancy: CT Pulmonary Angiography Versus Perfusion Scanning

OBJECTIVE The purpose of this study was to evaluate the equivalence of CT pulmonary angiography and perfusion scanning in terms of diagnostic quality and negative predictive value in the imaging of pulmonary embolism (PE) in pregnancy. MATERIALS AND METHODS Between 2000 and 2007 at a university hospital and a large private hospital, 199 pregnant patients underwent 106 CT pulmonary angiographic examinations and 99 perfusion scans. Image quality was evaluated, and the findings were reread by radiologists and compared with the original clinical readings. Three-month follow-up findings of PE and deep venous thrombosis were recorded. RESULTS PE was found in four of the 106 patients (3.7%) who underwent CT pulmonary angiography. The overall image quality was poor in 5.6% of cases, acceptable in 17.9%, and good in 76.4%. Fourteen CT and nine radiographic studies showed other clinically significant abnormalities. Six patients had indeterminate CT pulmonary angiographic findings, three had normal perfusion scans, and none underwent anticoagulation. All perfusion scan findings were normal. There was one incomplete study, and follow-up CT pulmonary angiography performed the same day showed PE. Two of 99 studies (2.02%) showed intermediate probability of the presence of PE; PE was not found at CT pulmonary angiography, but pneumonia was found. PE was found in one postpartum patient 9 weeks after she had undergone CT pulmonary angiography and ultrasound with normal findings. None of the patients died. CONCLUSION CT pulmonary angiography and perfusion scanning have equivalent clinical negative predictive value (99% for CT pulmonary angiography; 100% for perfusion scanning) and image quality in the care of pregnant patients. Therefore, the choice of study should be based on other considerations, such as radiation concern, radiographic results, alternative diagnosis, and equipment availability. Reducing the amount of radiation to the maternal breast favors use of perfusion scanning when the radiographic findings are normal and there is no clinical suspicion of an alternative diagnosis.

SPECT in acute pulmonary embolism

The purpose of this review was to evaluate the accuracy of SPECT in acute pulmonary embolism. Sparse data are available on the accuracy of SPECT based on an objective reference test. Several investigations were reported in which the reference standard for the diagnosis of pulmonary embolism was based in part on the results of SPECT or planar ventilation–perfusion (V/Q) imaging. The sensitivity of SPECT in all but one investigation was at least 90%, and specificity also was generally at least 90%. The sensitivity of SPECT in 4 of 5 investigations was higher than that of planar V/Q imaging. The specificity of SPECT was generally higher, equal, or only somewhat lower than that of planar V/Q imaging. Most investigators reported nondiagnostic SPECT V/Q scans in no more than 3% of cases. Methods of obtaining SPECT images, methods of obtaining planar V/Q images, and the criteria for interpretation varied. The general impression is that SPECT is more advantageous than planar V/Q imaging.

Challenges in the Diagnosis Acute Pulmonary Embolism

The state of the art of diagnostic evaluation of hemodynamically stable patients with suspected acute pulmonary embolism was reviewed. Diagnostic evaluation should begin with clinical assessment using a validated prediction rule in combination with measurement of D-dimer when appropriate. Imaging should follow only when necessary. Although with 4-slice computed tomography (CT) and 16-slice CT, the sensitivity for detection of pulmonary embolism was increased by combining CT angiography with CT venography, it is not known whether CT venography increases the sensitivity of 64-slice CT angiography. Methods to reduce the radiation exposure of CT venography include imaging only the proximal leg veins (excluding the pelvis) and obtaining discontinuous images. Compression ultrasound can be used instead. In young women, radiation of the breasts produces the greatest risk of radiation-induced cancer. It may be that scintigraphy is the imaging test of choice in such patients, but this pathway should be tested prospectively. A patient-specific approach to the diagnosis of pulmonary embolism can be taken safely in hemodynamically stable patients to increase efficiency and decrease cost and exposure to radiation.

Computed tomography of pulmonary thromboembolism and infarction

Computed tomographic findings in 18 patients with pulmonary thromboembolism are retrospectively reviewed. In the majority of patients, thromboembolism was not suspected clinically. The CT findings can be divided into two groups: vascular and parenchymal changes. The most frequent vascular findings is an intraluminal filling defect or defects due to thrombus. The most frequent parenchymal finding is a triangular (wedge-shaped) pleural-based soft tissue attenuation lesion. Although CT is not a primary diagnostic tool in the evaluation of pulmonary thromboembolism, CT may be helpful in diagnosis of pulmonary embolism, when evaluating an undiagnosed parenchymal density.