James G. Ravenel

CT Signs of Right Ventricular Dysfunction: Prognostic Role in Acute Pulmonary Embolism

OBJECTIVES The purpose of this study was to compare the prognostic role of various computed tomography (CT) signs of right ventricular (RV) dysfunction, including 3-dimensional ventricular volume measurements, to predict adverse outcomes in patients with acute pulmonary embolism (PE). BACKGROUND Three-dimensional ventricular volume measurements based on chest CT have become feasible for routine clinical application; however, their prognostic role in patients with acute PE has not been assessed. METHODS We evaluated 260 patients with acute PE for the following CT signs of RV dysfunction obtained on routine chest CT: abnormal position of the interventricular septum, inferior vena cava contrast reflux, right ventricle diameter (RVD) to left ventricle diameter (LVD) ratio on axial sections and 4-chamber (4-CH) views, and 3-dimensional right ventricle volume (RVV) to left ventricle volume (LVV) ratio. Comorbidities and fatal and nonfatal adverse outcomes according to the MAPPET-3 (Management Strategies and Prognosis in Pulmonary Embolism Trial-3) criteria within 30 days were recorded. RESULTS Fifty-seven patients (21.9%) had adverse outcomes, including 20 patients (7.7%) who died within 30 days. An RVD(axial)/LVD(axial) ratio >1.0 was not predictive for adverse outcomes. On multivariate analysis (adjusting for comorbidities), abnormal position of the interventricular septum (hazard ratio [HR]: 2.07; p = 0.007), inferior vena cava contrast reflux (HR: 2.57; p = 0.001), RVD(4-CH)/LVD(4-CH) ratio >1.0 (HR: 2.51; p = 0.009), and RVV/LVV ratio >1.2 (HR: 4.04; p < 0.001) were predictive of adverse outcomes, whereas RVD(4-CH)/LVD(4-CH) ratio >1.0 (HR: 3.68; p = 0.039) and RVV/LVV ratio >1.2 (HR: 6.49; p = 0.005) were predictive of 30-day death. CONCLUSIONS Three-dimensional ventricular volume measurement on chest CT is a predictor of early death in patients with acute PE, independent of clinical risk factors and comorbidities. Abnormal position of the interventricular septum, inferior vena cava contrast reflux, and RVD(4-CH)/LVD(4-CH) ratio are predictive of adverse outcomes, whereas RVD(axial)/LVD(axial) ratio >1.0 is not.

Reproducibility of CT Signs of Right Ventricular Dysfunction in Acute Pulmonary Embolism

OBJECTIVE The purpose of our study was to determine the interobserver reproducibility of CT findings of right ventricular (RV) dysfunction in pulmonary embolism (PE). MATERIALS AND METHODS Two experienced observers independently and retrospectively evaluated pulmonary CT angiography (CTA) studies of 50 patients with acute PE for the following signs: bowing of the interventricular septum, inferior vena cava (IVC) contrast medium reflux, RV diameter (RVD)/left ventricular diameter (LVD) ratio on axial sections and four-chamber (4-CH) views, and RV volume (RVV)/left ventricular volume (LVV) ratio. Analysis used kappa statistics, Spearmans rank correlation, and Bland-Altman statistics. RESULTS The two observers had fair to moderate agreement (kappa = 0.32-0.44) for septal bowing and moderate to good agreement (kappa = 0.57-0.68) for diagnosing IVC reflux. The Spearmans rank correlation coefficients for RVD(axial)/LVD(axial) ratio and RVD(4-CH)/LVD(4-CH) ratio between the two observers were 0.88 (p < 0.001) and 0.85 (p < 0.001), respectively. On Bland-Altman analysis, the mean differences for RVD(axial)/LVD(axial) ratio and RVD(4-CH)/LVD(4-CH) ratio were 0.014 (+/- 0.195) and 0.001 (+/- 0.242), respectively. The correlation coefficient for RVV/LVV ratio was 0.93 (p < 0.001), and the mean difference was 0.033 (+/- 0.229). CONCLUSION Considerable differences exist in the interobserver reproducibility of CT findings of RV dysfunction on pulmonary CTA in patients with acute PE. Cardiac chamber measurements are more reproducible than septal bowing and IVC reflux. Volumetric determination of the RVV/LVV ratio is the least user dependent and most reproducible.

Iso-Osmolality versus Low-Osmolality Iodinated Contrast Medium at Intravenous Contrast-enhanced CT: Effect on Kidney Function

PURPOSE To determine the effects of iso-osmolality contrast medium compared with a low-osmolality agent on renal function (serum creatinine [SCr] and glomerular filtration rate [GFR]) in high-risk patients undergoing intravenous contrast material-enhanced CT. MATERIALS AND METHODS This HIPAA-compliant study was IRB-approved; formal consent was obtained. One hundred seventeen patients (83 men, 34 women; mean age, 64.3 years; range, 18-86 years) with decreased renal function underwent contrast-enhanced CT with either iso-osmolality iodixanol (n = 61) or low-osmolality iopromide (n = 56). Outcome measures were of SCr increase or GFR decrease for 3 days after CT, a SCr increase (of >or=0.5 mg/dL [44.2 micromol/L, 25%] or >or=1.0 mg/dL [88.4 micromol/L, 50%]), a GFR reduction (of >or=5 mL/min), and patient outcome at 30- and 90-day follow-up. RESULTS Iodixanol decreased SCr (mean +/- standard deviation) from 1.77 mg/dL +/- 0.24 (156.47 micromol/L +/- 21.22) at baseline to 1.65 mg/dL +/- 0.35 (145.86 micromol/L +/- 30.94, P = .046) at day 1, 1.73 mg/dL +/- 0.53 (152.93 micromol/L +/- 46.85, not significant) at day 2, and 1.73 mg/dL +/- 0.55 (152.93 micromol/L +/- 48.62, not significant) at day 3 (not significant). Iopromide increased SCr from 1.75 mg/dL +/- 0.32 (154.7 micromol/L +/- 28.29) at baseline to 1.8 mg/dL +/- 0.42 (159.12 micromol/L +/- 15.59) at day 1, 1.77 mg/dL +/- 0.49 (156.47 micromol/L +/- 43.32) at day 2, and 1.77 mg/dL +/- 0.62 (156.47 micromol/L +/- 54.81) at day 3 (not significant). Iodixanol increased and iopromide decreased GFR on all 3 days after CT (not significant). Fewer patients in the iodixanol group (8.5%) than in the iopromide group (27.8%) had SCr increase 0.5 mg/dL or higher (>or=25%, P = .012). Two patients in each group had SCr increase of 1.0 mg/dL or more (not significant). More patients in the iopromide group (42.3%) than in the iodoxanol group (24.1%) had a GFR reduction of 5 mL/min or higher (P = .0426). No patient had a contrast material-related adverse event at 30- or 90-day follow-up. CONCLUSION Intravenous contrast material application in high-risk patients is unlikely to be associated with permanent adverse outcomes. SCr levels after contrast material administration are lower in iodixanol than iopromide groups.

Right Heart: Split-Bolus Injection of Diluted Contrast Medium for Visualization at Coronary CT Angiography

PURPOSE To retrospectively compare a split-bolus contrast medium injection protocol with a biphasic and a monophasic protocol in terms of visualization of the right and left heart, contrast medium-related streak artifacts, and level of attenuation in the cardiac chambers and coronary arteries at coronary computed tomographic (CT) angiography. MATERIALS AND METHODS The human research committee approved this HIPAA-compliant study and waived informed consent. Seventy-five patients had undergone 64-section coronary CT angiography: 25 were injected by using a monophasic, contrast-medium-only protocol with a single-syringe injector; 25 were injected by using a biphasic protocol with a dual-syringe injector; and 25 were injected by using a split-bolus protocol with a dual-syringe injector and an initial bolus of contrast medium followed by 50 mL of a 70%:30% saline-to-contrast medium mixture and a 30-mL saline chaser. Two radiologists rated the visualization of right and left heart structures and the degree of streak artifacts. One observer performed attenuation measurements of the cardiac chambers and of the coronary arteries. Data were analyzed with one-way analysis of variance and Duncan post-hoc multiple comparison procedures. RESULTS Data for 27 women and 48 men (mean age, 62 years) were included. Mean contrast medium attenuation in the right heart was significantly (P < .001) higher in the split-bolus group than in the biphasic injection group but was significantly (P < .001) lower than in the monophasic injection group. For the left heart and the coronary arteries, there were no significant differences among the three groups. Artifacts occurred less frequently (P < .001) in the biphasic and split-bolus groups than in the monophasic group. Visualization of right heart structures was rated significantly (P < .05) better in the split-bolus group than in the two other groups, while there was no difference for visualization of left heart structures. CONCLUSION Split-bolus injection provides sufficient attenuation for visualization of the right heart, while streak artifacts from high-attenuation contrast material can generally be avoided and arterial attenuation is maintained.

Acute Traumatic Aortic Injury: Imaging Evaluation and Management

Despite recent advances in prehospital care, multidetector computed tomographic (CT) technology, and rapid definitive therapy, trauma to the aorta continues to be a substantial source of morbidity and mortality in patients with blunt trauma. The imaging evaluation of acute aortic injuries has undergone radical change over the past decade, mostly due to the advent of multidetector CT. Regardless of recent technologic advances, imaging of the aorta in the trauma setting remains a multimodality imaging practice, and thus broad knowledge by the radiologist is essential. Likewise, the therapy for acute aortic injuries has changed substantially. Though open surgical repair continues to be the mainstay of therapy, percutaneous endovascular repair is becoming commonplace in many trauma centers. Here, the historical and current status of imaging and therapy of acute traumatic aortic injuries will be reviewed.

Pulmonary Nodule Volume: Effects of Reconstruction Parameters on Automated Measurements—A Phantom Study

PURPOSE To prospectively evaluate in a phantom the effects of reconstruction kernel, field of view (FOV), and section thickness on automated measurements of pulmonary nodule volume. MATERIALS AND METHODS Spherical and lobulated pulmonary nodules 3-15 mm in diameter were placed in a commercially available lung phantom and scanned by using a 16-section computed tomographic (CT) scanner. Nodule volume (V) was determined by using the diameters of 27 spherical nodules and the mass and density values of 29 lobulated nodules measured by using the formulas V = (4/3)pi r(3) (spherical nodules) and V = 1000 x (M/D) (lobulated nodules) as reference standards, where r is nodule radius; M, nodule mass; and D, wax density. Experiments were performed to evaluate seven reconstruction kernels and the independent effects of FOV and section thickness. Automated nodule volume measurements were performed by using computer-assisted volume measurement software. General linear regression models were used to examine the independent effects of each parameter, with percentage overestimation of volume as the dependent variable of interest. RESULTS There was no substantial difference in the accuracy of volume estimations across the seven reconstruction kernels. The bone reconstruction kernel was deemed optimal on the basis of the results of a series of statistical analyses and other qualitative findings. Overall, volume accuracy was significantly associated (P < .0001) with larger reference standard-measured nodule diameter. There was substantial overestimation of the volumes of the 3-5-mm nodules measured by using the volume measurement software. Decreasing the FOV facilitated no significant improvement in the precision of lobulated nodule volume measurements. The accuracy of volume estimations--particularly those for small nodules--was significantly (P < .0001) affected by section thickness. CONCLUSION Substantial, highly variable overestimation of volume occurs with decreasing nodule diameter. A section thickness that enables the acquisition of at least three measurements along the z-axis should be used to measure the volumes of larger pulmonary nodules.

Accuracy of EUS in staging of T4 lung cancer

BACKGROUND Increasingly, EUS is being used to stage lung cancer. Direct mediastinal invasion (T4) by lung cancer is stage IIIb disease. Patients in this stage have a 5-year survival of less than 5% and generally are offered chemotherapy without surgery. This study evaluated the accuracy of EUS in detecting T4 lung cancer. METHODS The study included all patients with lung cancer who had EUS staging and subsequent staging at surgery, or for whom there was unequivocal confirmation of unresectability (T4) by thoracoscopy, thoracotomy or presence of malignant pleural effusion, or definite invasion of great vessels/adjacent organs on CT. RESULTS A total of 175 of 308 patients with lung cancer who underwent EUS over a 5-year period (1997-2002) had subsequent confirmatory tumor staging. Ten patients were found by EUS to have stage T4 tumors; 7 were confirmed to be T4 by either surgical exploration (2), CT demonstration of aortic invasion (3), or documentation of malignant pleural effusion (2). Three of the 10 (30%) patients found to have stage T4 tumors by EUS had T2 disease at surgery and underwent curative resection. Of the remaining 165 patients without evidence of T4 disease at EUS, only one was found to have aortic invasion (T4) at surgery. EUS had a sensitivity of 87.5%, specificity of 98%, positive predictive value of 70%, and a negative predictive value of 99% for detecting T4 disease. CONCLUSIONS Caution is warranted when unresectability of lung cancer is based solely on tumor invasion into mediastinal soft tissue at EUS. Overstaging occurs when a tumor appears to invade the pleural layer without mediastinal organ invasion. Confirmation of unresectability by other diagnostic modalities is warranted in such instances.

Multidimensional imaging of the thorax: practical applications.

Over the past decade, faster CT scan times, thinner collimation, and the development of multirow detectors, coupled with the increasing capability of computers to process large amounts of data in short periods of time, have lead to an expansion in the ability to create diagnostically useful two-dimensional (2D) and three-dimensional (3D) images within the thorax. Applications within the thorax include, but are not limited to, evaluation of pulmonary and systemic vasculature, evaluation of the tracheobronchial tree, and delineation of diffuse lung disease. Pulmonary nodule volume and growth can be more accurately predicted, and represents an improvement in the evaluation of the solitary pulmonary nodule. Multiplanar images increase our understanding of thoracic anatomy and can help to guide bronchoscopic procedures. Because there are strengths and weaknesses to all the reconstruction algorithms, the utility of any given technique is dependent on the clinical question to be answered. For instance, although maximum intensity projection imaging (MIP) is helpful in the evaluation of micronodular lung disease, it is of little value in the diagnosis of aortic dissection. As the ability to generate faster and more precise multidimensional images grow, the demand for such imaging is likely to increase. In this review, the authors discuss the various reconstruction techniques available, followed by a discussion of the clinical applications.

How Do Radiographic Techniques Affect Image Quality and Patient Doses in CT

The radiation dose received by patients who undergo CT examinations has become a subject of considerable interest. Adult effective doses for head CT examinations are of the order of 1 to 2 mSv, and for single body examinations, patient doses are typically between 4 and 6 mSv. These doses are high in comparison to most other types of radiological examinations that use ionizing radiation. Patient CT doses may also be compared with natural background (3 mSv/year), dose limits to members of the public (1 mSv/year), and the highest level of occupational exposure, which is about 5 mSv/year. The advent of multi-slice technology will serve to increase CT utilization, as well as individual doses for any given examination. Radiologists are responsible for medical radiation doses to their patients, and it is imperative that they understand the relationship between radiation dose and image quality. In this review, we address the impact that variations in radiographic techniques (ie, selected values of X-ray kVp and mAs) have on patient doses as well as the quality of the resultant CT images.

Association of Coronary Artery Calcification and Mortality in the National Lung Screening Trial: A Comparison of Three Scoring Methods

PURPOSE To evaluate three coronary artery calcification (CAC) scoring methods to assess risk of coronary heart disease (CHD) death and all-cause mortality in National Lung Screening Trial (NLST) participants across levels of CAC scores. MATERIALS AND METHODS The NLST was approved by the institutional review board at each participating institution, and informed consent was obtained from all participants. Image review was HIPAA compliant. Five cardiothoracic radiologists evaluated 1575 low-dose computed tomographic (CT) scans from three groups: 210 CHD deaths, 315 deaths not from CHD, and 1050 participants who were alive at conclusion of the trial. Radiologists used three scoring methods: overall visual assessment, segmented vessel-specific scoring, and Agatston scoring. Weighted Cox proportional hazards models were fit to evaluate the association between scoring methods and outcomes. RESULTS In multivariate analysis of time to CHD death, Agatston scores of 1-100, 101-1000, and greater than 1000 (reference category 0) were associated with hazard ratios of 1.27 (95% confidence interval: 0.69, 2.53), 3.57 (95% confidence interval: 2.14, 7.48), and 6.63 (95% confidence interval: 3.57, 14.97), respectively; hazard ratios for summed segmented vessel-specific scores of 1-5, 6-11, and 12-30 (reference category 0) were 1.72 (95% confidence interval: 1.05, 3.34), 5.11 (95% confidence interval: 2.92, 10.94), and 6.10 (95% confidence interval: 3.19, 14.05), respectively; and hazard ratios for overall visual assessment of mild, moderate, or heavy (reference category none) were 2.09 (95% confidence interval: 1.30, 4.16), 3.86 (95% confidence interval: 2.02, 8.20), and 6.95 (95% confidence interval: 3.73, 15.67), respectively. CONCLUSION By using low-dose CT performed for lung cancer screening in older, heavy smokers, a simple visual assessment of CAC can be generated for risk assessment of CHD death and all-cause mortality, which is comparable to Agatston scoring and strongly associated with outcome.