Computed tomographic angiography in acute pulmonary embolism: do we need multiplanar reconstructions to evaluate the right ventricular dysfunction?

PURPOSE: To compare the indices of right ventricular dysfunction (RVD) obtained from axial transverse images with those derived from the reconstructed 4-chamber and short-axis views in patients with acute pulmonary embolism (PE). MATERIALS AND METHODS: Eighty-eight patients with acute PE were retrospectively enrolled. For each patient, axial transverse images and reconstructed 4-chamber and short-axis views were reviewed. Measurements of the ratios of right ventricle to left ventricle (RV/LV) diameters and RV/LV areas were then obtained from all series. Values derived from each method were compared and correlated to arterial obstruction index. RESULTS: In the studied cohort, RV/LV diameters and RV/LV areas obtained from axial transverse images and the reconstructed 4-chamber views were not statistically different. In contrast, a statistically significant difference was observed between the values of RV/LV areas derived from both axial transverse and 4-chamber views and those obtained from short-axis views (P < 0.0001). There was a weak to moderate correlation between both RV/LV diameters and RV/LV areas and the computed tomographic obstruction index. However, when the study cohort was divided into 3 subgroups with an arterial obstruction index of less than 15% (n = 26), 15% to 30% (n = 21), and greater than 30% (n = 41), those who had values greater than 30% revealed the highest correlation with the indices of RVD. CONCLUSIONS: In patients with acute PE, the indices of RVD derived from axial transverse images and the reconstructed 4-chamber views yield comparative values. Given the simplicity of the former analysis, it should be taken into consideration for risk stratification in acute PE.     

Thrombus load and acute right ventricular failure in pulmonary embolism: correlation and demonstration of a “tipping point” on CT pulmonary angiography

Objectives

The aim of this study was to determine the correlation between increasing pulmonary embolism thrombus load and right ventricular (RV) dilatation as demonstrated by CT pulmonary angiography (CTPA) and to assess the thrombus load threshold which indicates impending RV decompensation.

Methods

2425 consecutive CTPAs were retrospectively analysed. Thrombus load using a modified Miller score (MMS), RV to left ventricular (RV:LV) ratio, presence of septal shift, and pulmonary artery and aorta size were analysed in 504 positive CTPA scans and a representative cohort of 100 negative scans. Results were correlated using non-parametric analysis (two-tailed t-test or χ² test) and Pearson’s rank correlation.

Results

Increasing thrombus load correlated with a higher RV:LV ratio, with a statistically significant difference in RV:LV ratios between the negative and positive pulmonary embolism (PE) cohorts. Larger thrombus loads (MMS ≥12 vs MMS <12) were strongly correlated with RV strain (mean RV:LV ratio, 1.323 vs 0.930; p<0.0001). Smaller thrombus loads had no significant influence on RV strain. Septal shift was also more likely with an MMS of ≥12, as was an increase in pulmonary artery diameter (r=0.221, p<0.001).

Conclusion

With increasing thrombus load in PE, there is CTPA evidence of RV decompensation with an MMS threshold of 12. This suggests a “tipping point” beyond which RV decompensation is more likely to occur. This is the first study to describe this tipping point between a thrombus load of MMS >12 and an increase in RV:LV ratio. This finding may help to improve risk stratification in patients with acute PE diagnosed by CTPA.Acute pulmonary embolism (PE) remains a diagnostic challenge for physicians and accounts for significant morbidity and mortality in hospitalised patients. In the United Kingdom, the incidence of proven PE is 60–70 per 100 000 in the population and mortality rates range from 6% to 15%. Clinical manifestations vary widely, from asymptomatic patients with small peripheral emboli to patients who present with circulatory collapse and large thromboembolic loads who may warrant thrombolysis. Between these extremes, there is a significant group presenting with PE who have apparent clinical haemodynamic stability but demonstrate radiological findings (e.g. via echocardiography or CT pulmonary angiography) or biomarkers [such as B-type natriuretic peptide (BNP) or troponin] of right heart strain, in whom the prognosis may be poorer and for whom the role of thrombolysis has not been established [1-4]. Studies to date have demonstrated that right heart strain is associated with higher mortality than no right heart strain [5,6], and CT assessment of right heart strain correlates with echocardiographic findings [7].CT pulmonary angiography (CTPA) has been established as the imaging modality of choice for the initial diagnosis of pulmonary thromboembolism [8,9], and is also used for assessing right ventricular (RV) afterload [10,11]. In addition, it enables quantification of thrombus load, for which a variety of scoring systems are available. These include the modified Miller score (MMS), a catheter pulmonary angiography score [12] adapted for CTPA by Bankier et al [13], and more complex systems such as the Qanadli and Mastora scores [14,15]. The aim of this study was to determine if there is a correlation between increasing thrombus load using MMS and RV dilatation as a predictor of RV failure according to CTPA findings.     

Dual energy CT pulmonary blood volume assessment in acute pulmonary embolism �C correlation with D-dimer level, right heart strain and clinical outcome

Objective  

To investigate the role of perfusion defect (PD) size on dual energy CT pulmonary blood volume assessment as predictor of right heart strain and patient outcome and its correlation with d-dimer levels in acute pulmonary embolism (PE).     

Does lung perfusion scintigraphy continue to have a role in the clinical management of patients suspected of pulmonary embolism in the CT pulmonary angiography era?

Objective

Acute pulmonary embolism (PE) is a life-threatening disorder with high mortality. A prompt diagnosis and treatment is essential for reducing the mortality rate. The purpose of the study is to evaluate if lung perfusion scintigraphy (LPS) continues to have a role in the clinical management of patients suspected of pulmonary embolism in the CT pulmonary angiography (CTPA) era.

Methods

For this study, 1183 patients who had been subjected to LPS were retrospectively evaluated and classified into the following groups: A (positive LPS), B (negative LPS) and C (indeterminate LPS). Patients were further classified into A1 (‘PE likely’ and LPS-negative), B1 (PE unlikely and LPS-positive) and C1 (PE likely and indeterminate LPS) by combining the LPS findings and the clinical pretest probability (cpp). Subgroups A1, B1 and C1 underwent additional CTPA.

Results

Groups A, B, and C included 1086/1183, 69/1183 and 28/1183 patients, respectively. The proportion of patients with inconsistent cpp LPS findings who underwent additional CTPA was 106/1183 patients: subgroup A1 (n?=?73), B1 (n?=?21), and C1 (n?=?12). In subgroup A1, CTPA was negative in 61/73, non-diagnostic in 12/73 and positive in 0/73 patients. In subgroup B1, CTPA excluded PE in 2/21, non-diagnostic in 3/21 and positive in 16/21 patients. In group C1, CTPA was negative in 8/12, positive in 2/12 and non-diagnostic in 2/12 patients.

Conclusion

In the CTPA era, LPS continues to have a role in the clinical management of patients suspected of PE.

     

Dual-energy CT angiography of chronic thromboembolic disease: Can it help recognize links between the severity of pulmonary arterial obstruction and perfusion defects?

Purpose

To evaluate whether dual-energy CT angiography (DE-CTA) could identify links between morphologic and functional abnormalities in chronic pulmonary thromboembolism (CPTE).

Materials and methods

Seventeen consecutive patients with CPTE without underlying cardio-respiratory disease were investigated with DE-CTA. Two series of images were generated: (a) transverse diagnostic scans (i.e., contiguous 1-mm thick averaged images from both tubes), and (b) perfusion scans (i.e., images of the iodine content within the microcirculation; 4-mm thick MIPs). Two radiologists evaluated by consensus the presence of: (a) pulmonary vascular features of CPTE and abnormally dilated systemic arteries on diagnostic CT scans, and (b) perfusion defects of embolic type on perfusion scans.

Results

Diagnostic examinations showed a total of 166 pulmonary arteries (166/833; 19.9%) with features of CPTE, more frequent at the level of peripheral than central arteries (8.94 vs 0.82; p < 0.0001), including severe stenosis with partial (97/166; 58.4%) or complete (20/166; 12.0%) obstruction, webs and bands (37/166; 22.3%), partial filling defects without stenosis (7/166; 4.2%), focal stenosis (4/166; 2.4%) and abrupt vessel narrowing (1/166; 0.6%). Perfusion examinations showed 39 perfusion defects in 8 patients (median number: 4.9; range: 1-11). The most severe pulmonary arterial features of CPTE were seen with a significantly higher frequency in segments with perfusion defects than in segments with normal perfusion (p < 0.0001). Enlarged systemic arteries were observed with a significantly higher frequency ipsilateral to lungs with perfusion defects (9/12; 75%) compared with lungs without perfusion defects (5/22; 22.7%) (p = 0.004).

Conclusion

Dual-energy CTA demonstrates links between the severity of pulmonary arterial obstruction and perfusion impairment, influenced by the degree of development of the systemic collateral supply.     

Chest ultrasound in the evaluation of complicated pneumonia in the ICU patients: Can be viable alternative to CT?

Objective

To compare ultrasound (US) and computed tomography (CT) for evaluating patients with complicated pneumonia admitted to the intensive care unit (ICU) to assess if US can be an alternative to CT.

Subjects and methods

We prospectively compared US and CT findings in 48 patients admitted to the ICU with complicated pneumonia with their final diagnosis at discharge. Images were evaluated for parenchymal findings (consolidation, necrosis, and abscess) and pleural findings (effusion, loculation or fibrin strands in the pleural fluid).

Results

US was similar to CT in the evaluation of parenchymal and pleural abnormalities except for two patients with consolidation and effusion, three patients with loculated effusion, one patient with pulmonary necrosis and another patient with lung abscess. US was superior to CT in detection of fibrin strands within pleural effusion.

Conclusion

Chest US provides an accurate evaluation of the pleural and parenchymal abnormalities associated with complicated pneumonia in the ICU patients. Considering that chest US is a bedside and avoids transportation of the patient outside ICU, free of radiation exposure and easily repeatable, chest US appears to be an attractive alternative to CT.     

Oral contrast for CT in patients with acute non-traumatic abdominal and pelvic pain: what should be its current role?

Positive oral contrast agents, including barium suspensions and water-soluble iodinated solutions, have traditionally been used in conjunction with the CT evaluation of patients with abdominal and pelvic pain. Due to continued advancements in CT technology, and due to increasing obesity and correspondingly a general increase in the intra-abdominal and intra-pelvic fat separating bowel loops in North American patients and in patients in other parts of the world over the past few decades, the ability of radiologists to accurately evaluate the cause of acute symptoms has substantially improved. Recent research and evolving imaging society guidelines/systematic reviews increasingly support performing CT scans of the abdomen and pelvis without the need for positive oral contrast in these types of adult patient populations, in most clinical situations. Increased patient throughput, patient preference, patient safety, and most importantly, retention of high diagnostic accuracy, are reasons for this recent change in practice to routinely omit the use of enteric contrast agents for the majority of patients presenting with acute abdominal and pelvic pain whom are undergoing emergency CT.     

Is TOMPOOL (gated blood-pool SPECT processing software) accurate to diagnose right and left ventricular dysfunction in a clinical setting?

Background

The assessment of right ventricular function is crucial for management of heart disease. TOMPOOL is a software that processes data acquired with Tomographic Equilibrium Radionuclide Ventriculography. In this report, TOMPOOL’s diagnostic accuracy and inter-observer reproducibility were assessed in a cohort of patients with various etiologies of ventricular dysfunction.

Methods and Results

End-diastolic volume (EDV), ejection fraction (EF), and cardiac output (CO) were calculated for the right ventricle (RV) and the left ventricle (LV) using TOMPOOL in 99 consecutive patients. Thirty-five patients underwent cardiac magnetic resonance imaging (CMR) considered as the reference-standard to measure EDV and EF; the Spearman’s rho correlation coefficients were r = 0.73/0.80 and 0.67/0.73 for right/left EF and EDV, respectively. Twenty-one patients had thermodilution measurements of right CO (reference-standard), the correlation was r = 0.57. The best cut-off points (sensitivity/specificity) in order to diagnose a ventricular dysfunction or enlargement were 46% for RVEF (67%/89%), 62% for LVEF (100%/90%), 94 mL for RVEDV (77%/73%), and 84 mL for LVEDV (100%/91%). The areas under the ROC curve were, respectively, 0.79, 0.91, 0.83, and 0.99. Inter-observer reproducibility was r = 0.81/0.94, 0.77/0.90, and 0.78/0.75 for Right/Left EF, EDV, and CO, respectively.

Conclusion

TOMPOOL is accurate: measurements of EDV, EF, and CO are reproducible and correlate with CMR and thermodilution. However, thresholds must be adjusted.     

Radiologic-pathologic correlation in acute appendicitis: can we use it as a quality measure to assess interpretive accuracy of radiologists?

Radiologic–pathologic correlation was evaluated as a quality assurance tool by documenting error rates of 18 radiologists interpreting computed tomographic (CT) scans for acute appendicitis in 763 patients. The departmental error rate was 3.1%. Meaningful individual error rates could be determined in only the seven radiologists who interpreted ≥30 CT scans for acute appendicitis. Radiologic–pathologic correlation is an effective departmental monitor of interpretive accuracy, but individual accuracy can be assessed only for radiologists reading a large number of cases with pathologic proof.     

Can exercise renography be an alternative to ACE inhibitor renography in hypertensive patients who are suspicious for renal artery stenosis?

The aim of this study was to evaluate the value of Tc-99m ethylenedicysteine exercise renography in patients with hypertension who were suspicious for renal artery stenosis and compare the results with captopril renography. METHODS: Twenty-nine patients with hypertension who were highly suspect for having renal artery stenosis were included in the study. Basal captopril exercise renograms were performed within 1 week in all patients with Tc-99m EC. Exercise was performed with a bicycle ergometer as described in the literature. Interpretations of renograms were made according to the consensus report on angiotensin converting enzyme (ACE) inhibitor renography as high, low, or intermediate probability. The sensitivity, specificity, and positive and negative predictive values were also obtained on both the kidneys and a patient basis. The results were compared with renal angiography in 19 patients. RESULTS: Twenty of 29 patients had concordant results with both captopril and exercise studies. All discordant tests were normal with captopril but positive with exercise renograms. Nineteen patients with 38 kidneys were included for statistical data analysis. Nine kidneys, which were either atrophic or abnormal during the basal study, were excluded from the kidney-based analysis. With contrast angiography, 8 patients had renal artery stenosis. When evaluated on a kidney basis, the sensitivity, specificity, and positive and negative predictive values for captopril scans were 87%, 100%, 100%, and 95%, and for the exercise scans were 100%, 90%, 80%, and 100% respectively. When calculated on a patient basis with regard to the captopril scans, the sensitivity, specificity, and positive and negative predictive values were 87%, 81%, 77%, and 88%, and for exercise scans were 100%, 54%, 61%, and 100% respectively. There were 2 false-positive exercise scans that were found to be the result of dilated minor collecting systems and changes in kidney contours as a result of motion during exercise. CONCLUSIONS: These results indicate that exercise renography has a similar sensitivity but lower specificity compared with captopril scintigraphy in the diagnosis of renal artery stenosis. Because of the lower specificity, its use in the screening of renovascular hypertension may be limited. Exercise renography may be more useful as an investigative tool for essential hypertension.     

Does direct MR galactography have the potential to become an alternative diagnostic tool in patients with pathological nipple discharge?

Purpose

To compare direct magnetic resonance galactography (dMRG) and conventional galactography (CGal).

Materials and Methods

Thirty women underwent CGal and dMRG. Duct localization and the depth of the assumed underlying pathology in CGal and dMRG were analyzed.

Results

Comparing CGal and dMRG, there was no significant difference regarding sector localization, but for depth of pathology (P=.023).

Conclusion

Duct localization with dMRG was possible with the same reliability as with CGal. Thus, dMRG may have the potential to become an alternative method to CGal.     

Is body weight the most appropriate criterion to select patients eligible for low-dose pulmonary CT angiography? Analysis of objective and subjective image quality at 80 kVp in 100 patients

The objective of this retrospective study was to assess image quality with pulmonary CT angiography (CTA) using 80 kVp and to find anthropomorphic parameters other than body weight (BW) to serve as selection criteria for low-dose CTA. Attenuation in the pulmonary arteries, anteroposterior and lateral diameters, cross-sectional area and soft-tissue thickness of the chest were measured in 100 consecutive patients weighing less than 100 kg with 80 kVp pulmonary CTA. Body surface area (BSA) and contrast-to-noise ratios (CNR) were calculated. Three radiologists analyzed arterial enhancement, noise, and image quality. Image parameters between patients grouped by BW (group 1: 0–50 kg; groups 2–6: 51–100 kg, decadally increasing) were compared. CNR was higher in patients weighing less than 60 kg than in the BW groups 71–99 kg (P between 0.025 and <0.001). Subjective ranking of enhancement (P = 0.165–0.605), noise (P = 0.063), and image quality (P = 0.079) did not differ significantly across all patient groups. CNR correlated moderately strongly with weight (R = −0.585), BSA (R = −0.582), cross-sectional area (R = −0.544), and anteroposterior diameter of the chest (R = −0.457; P < 0.001 all parameters). We conclude that 80 kVp pulmonary CTA permits diagnostic image quality in patients weighing up to 100 kg. Body weight is a suitable criterion to select patients for low-dose pulmonary CTA.     

Can a state-of-the-art D-dimer test be used to determine the need for CT imaging in patients suspected of having pulmonary embolism?

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether a simple rapid blood test can obviate computed tomography (CT) in a sizable percentage of patients suspected of having pulmonary embolism, based on the hypothesis that negative D-dimer results could eliminate any further search for pulmonary embolism. MATERIALS AND METHODS: At the authors' institution, 2,121 sequential patients underwent a whole-blood antibody agglutination test for cross-linked fibrin degradation products (D-dimer). Of these patients, 844 had positive test results and were not further considered. A retrospective review included reports of all multisection combined CT venographic and pulmonary angiographic studies obtained within 48 hours of the D-dimer assay for the 1,277 patients with negative D-dimer results; 229 (18%) of these 1,277 patients underwent combined CT venography and pulmonary angiography, usually within 24 hours. RESULTS: Retrospective review of the imaging examinations that were discrepant with the D-dimer results revealed only three false-negative D-dimer results. Of the 229 patients in whom combined CT venography and pulmonary angiography was performed for suspected pulmonary embolism, 226 (98.7%) had no evidence of acute pulmonary embolism or deep venous thrombosis. The negative predictive value of a negative D-dimer result was therefore 98.7% (confidence interval, 96.2%-99.7%). CONCLUSION: The D-dimer assay is a simple rapid blood test that is sensitive to the presence of acute thrombosis. Very few patients with negative results have acute deep venous thrombosis or pulmonary embolism, with combined CT venography and pulmonary angiography used as the reference standard.     

Assessment of tumor heterogeneity by CT texture analysis: Can the largest cross-sectional area be used as an alternative to whole tumor analysis?

Objective

To determine if there is a difference between contrast enhanced CT texture features from the largest cross-sectional area versus the whole tumor, and its effect on clinical outcome prediction.

Methods

Entropy (E) and uniformity (U) were derived for different filter values (1.0–2.5: fine to coarse textures) for the largest primary tumor cross-sectional area and the whole tumor of the staging contrast enhanced CT in 55 patients with primary colorectal cancer. Parameters were compared using non-parametric Wilcoxon test. Kaplan–Meier analysis was performed to determine the relationship between CT texture and 5-year overall survival.

Results

E was higher and U lower for the whole tumor indicating greater heterogeneity at all filter levels (1.0–2.5): median (range) for E and U for whole tumor versus largest cross-sectional area of 7.89 (7.43–8.31) versus 7.62 (6.94–8.08) and 0.005 (0.004–0.01) versus 0.006 (0.005–0.01) for filter 1.0; 7.88 (7.22–8.48) versus 7.54 (6.86–8.1) and 0.005 (0.003–0.01) versus 0.007 (0.004–0.01) for filter 1.5; 7.88 (7.17–8.54) versus 7.48 (5.84–8.25) and 0.005 (0.003–0.01) versus 0.007 (0.004–0.02) for filter 2.0; and 7.83 (7.03–8.57) versus 7.42 (5.19–8.26) and 0.005 (0.003–0.01) versus 0.006 (0.004–0.03) for filter 2.5 respectively (p ≤ 0.001). Kaplan–Meier analysis demonstrated better separation of E and U for whole tumor analysis for 5-year overall survival.

Conclusion

Whole tumor analysis appears more representative of tumor heterogeneity.     

Can multimodality imaging using 18F-FDG/18F-FLT PET/CT benefit the diagnosis and management of patients with pulmonary lesions?

Purpose

Dual-tracer, ¹⁸F-fluorodeoxyglucose and ¹⁸F-fluorodeoxythymidine (¹⁸F-FDG/¹⁸F-FLT), dual-modality (positron emission tomography and computed tomography, PET/CT) imaging was used in a clinical trial on differentiation of pulmonary nodules. The aims of this trial were to investigate if multimodality imaging is of advantage and to what extent it could benefit the patients in real clinical settings.

Methods

Seventy-three subjects in whom it was difficult to establish the diagnosis and determine management of their pulmonary lesions were prospectively enrolled in this clinical trial. All subjects underwent ¹⁸F-FDG and ¹⁸F-FLT PET/CT imaging sequentially. The images were interpreted with different strategies as either individual or combined modalities. The pathological or clinical evidence during a follow-up period of more than 22?months served as the standard of truth. The diagnostic performance of each interpretation and their impact on clinical decision making was investigated.

Results

¹⁸F-FLT/¹⁸F-FDG PET/CT was proven to be of clinical value in improving the diagnostic confidence in 28 lung tumours, 18 tuberculoses and 27 other benign lesions. The ratio between maximum standardized uptake values of ¹⁸F-FLT and ¹⁸F-FDG was found to be of great potential in separating the three subgroups of patients. The advantage could only be obtained with the full use of the multimodality interpretation. Multimodality imaging induced substantial change in clinical management in 31.5% of the study subjects and partial change in another 12.3%.

Conclusion

Multimodality imaging using ¹⁸F-FDG/¹⁸F-FLT PET/CT provided the best diagnostic efficacy and the opportunity for better management in this group of clinically challenging patients with pulmonary lesions.     

Variability and accuracy of coronary CT angiography including use of iterative reconstruction algorithms for plaque burden assessment as compared with intravascular ultrasound—an ex vivo study

Objectives

To systematically assess inter-technique and inter-/intra-reader variability of coronary CT angiography (CTA) to measure plaque burden compared with intravascular ultrasound (IVUS) and to determine whether iterative reconstruction algorithms affect variability.

Methods

IVUS and CTA data were acquired from nine human coronary arteries ex vivo. CT images were reconstructed using filtered back projection (FBPR) and iterative reconstruction algorithms: adaptive-statistical (ASIR) and model-based (MBIR). After co-registration of 284 cross-sections between IVUS and CTA, two readers manually delineated the cross-sectional plaque area in all images presented in random order.

Results

Average plaque burden by IVUS was 63.7?±?10.7% and correlated significantly with all CTA measurements (r?=?0.45–0.52; P?P?>?0.05). Increased overestimation was associated with smaller plaques, eccentricity and calcification (P?P?P?>?0.05).

Conclusion

In ex vivo coronary arteries, plaque burden by coronary CTA had extremely low inter-/intra-reader variability and correlated significantly with IVUS measurements. Accuracy as well as reader reliability were independent of CT image reconstruction algorithm.

Key Points

? IVUS is deemed the gold standard in-vivo coronary plaque assessment ? But coronary CT angiography findings correlate strongly with IVUS results ? Coronary CT angiography now allows plaque quantification close to IVUS ? Iterative image reconstruction algorithms do not alter accuracy or reproducibility ? Plaque quantification is more challenging in smaller eccentric calcified lesions     

Can CT replace bronchoscopy in the detection of the site and cause of bleeding in patients with large or massive hemoptysis?

OBJECTIVE: We assessed the capacity of chest radiography and CT to determine the cause and site of bleeding in patients with either large or massive hemoptysis compared with bronchoscopy. MATERIALS AND METHODS: We reviewed the chest radiographs, CT scans, and bronchoscopic findings in 80 patients with either large or massive hemoptysis who were admitted to our intensive care unit between January 1995 and June 1999. RESULTS: Findings on chest radiography were normal in only 13% of patients, of whom 70% had bronchiectasis. The chest radiographs revealed the site of bleeding in 46% of the patients and the cause in 35%, most of whom had tuberculosis or tumors. CT was more efficient than bronchoscopy for identifying the cause of bleeding (77% vs 8%, respectively; p < 0.001), whereas the two methods were comparable for identifying the site of bleeding (70% vs 73%, respectively; p = not significant). CONCLUSION: These data suggest that CT could replace bronchoscopy as the first-line procedure for screening patients with large and those with massive hemoptysis. However, these results must be confirmed in a prospective multicenter study.