Eun Jin Chae

Clinical Utility of Dual-Energy CT in the Evaluation of Solitary Pulmonary Nodules: Initial Experience

PURPOSE To determine the clinical utility of dual-energy computed tomography (CT) in evaluating solitary pulmonary nodules (SPNs). MATERIALS AND METHODS This study was approved by the institutional review board, and informed consent was obtained. CT scans were obtained before and 3 minutes after contrast material injection in 49 patients (26 men, 23 women; mean age, 60.39 years +/- 12.24 [standard deviation]) by using a scanner with a dual-energy technique. Image sets that included nonenhanced weighted average, enhanced weighted average, virtual nonenhanced, and iodine-enhanced images were reconstructed. CT numbers of SPNs on virtual nonenhanced and nonenhanced weighted average images were compared, and CT numbers on iodine-enhanced image and the degree of enhancement were compared. Diagnostic accuracy for malignancy by using CT number on iodine-enhanced image and the degree of enhancement were compared. On the virtual nonenhanced image, the number and size of calcifications were compared with those on the nonenhanced weighted average image. Radiation dose was compared with that of single-energy CT. RESULTS CT numbers on virtual nonenhanced and nonenhanced weighted average images and CT numbers on the iodine-enhanced image and the degree of enhancement showed good agreements (intraclass correlation coefficients: 0.83 and 0.91, respectively). Diagnostic accuracy for malignancy by using CT numbers on iodine-enhanced image was comparable to that by using the degree of enhancement (sensitivity, 92% and 72%; specificity, 70% and 70%; accuracy, 82.2% and 71.1%, respectively). On virtual nonenhanced image, 85.0% (17 of 20) of calcifications in the SPN and 97.8% (44 of 45) of calcifications in the lymph nodes were detected, and the apparent sizes were smaller than those on the nonenhanced weighted average image. Radiation dose (average dose-length product, 240.77 mGy cm) was not significantly different from that of single-energy CT (P = .67). CONCLUSION Dual-energy CT allows measurement of the degree of enhancement and detection of calcifications without additional radiation dose.

Xenon Ventilation CT with a Dual-Energy Technique of Dual-Source CT: Initial Experience

Institutional review board approval and written informed consent were obtained. Although xenon (Xe) ventilation CT has been introduced as a potential method with which to depict regional ventilation, quantification of Xe enhancement has been limited by the variability of lung attenuation caused by different lung volumes between scans. The purpose of this study was to assess the feasibility of Xe ventilation CT with a dual-energy technique. Dual-energy CT was performed in 12 subjects after Xe inhalation. With use of a dual-energy technique, the Xe component could be extracted without any influence from lung volume. Dynamic and static regional ventilation function can be displayed with an exact match to the thin-section CT image.

Dual-Energy CT for Assessment of the Severity of Acute Pulmonary Embolism: Pulmonary Perfusion Defect Score Compared With CT Angiographic Obstruction Score and Right Ventricular/Left Ventricular Diameter Ratio

OBJECTIVE The purpose of this study was to prospectively evaluate the usefulness of scoring perfusion defects on perfusion images at dual-energy CT for assessment of the severity of pulmonary embolism. SUBJECTS AND METHODS Thirty patients (13 men, 17 women; mean age, 55 +/- 15 [SD] years; range, 26-81 years) with pulmonary thromboembolism underwent dual-source CT at two voltages (140 and 80 kV). The weighted average image of two acquisitions was used for CT angiograms, and a color-coded iodine image was used for perfusion images. Two thoracic radiologists with 15 and 6 years of clinical experience independently assigned perfusion defect scores to perfusion images and both a CT angiographic (CTA) obstruction score and right ventricular-to-left ventricular (RV/LV) diameter ratio to CT angiograms. The CTA obstruction score was based on the Qanadli method. The perfusion defect score was defined as Sigma (n . d) / 40 x 100, where n is the number of segments and d is the degree of perfusion from 0 to 2. Correlations between perfusion defect score, CTA obstruction score, and RV/LV diameter ratio were evaluated. Agreement between perfusion defect score and CTA score was assessed per patient and per segment. Interobserver agreement regarding perfusion defect and CTA obstruction scores was analyzed. RESULTS Perfusion defect and CTA obstruction scores had good correlation with RV/LV diameter ratio (r = 0.69, r = 0.66; all p < 0.001). Per patient, correlation between perfusion defect score and CTA obstruction score also was good (reader 1, r = 0.87; reader 2, r = 0.85; all p < 0.001). Per segment, moderate agreement was found between perfusion defect score and CTA obstruction score (reader 1, kappa = 0.56; reader 2, kappa = 0.51; all p < 0.05). Both readers were in strong agreement on perfusion defect score and CTA obstruction score. CONCLUSION The proposed perfusion defect score had good correlation with RV/LV diameter ratio and CTA obstruction score. Therefore, acquisition of perfusion images at dual-energy CT may be helpful for assessing the severity of acute pulmonary embolism.

Radiologic and clinical findings of Behçet disease: comprehensive review of multisystemic involvement.

Behçet disease is a chronic, relapsing, systemic disorder of unknown etiology, characterized by recurrent oral and genital ulcers, uveitis, and other clinical manifestations in multiple organ systems. Although the diagnosis is made on the basis of the combination of typical clinical symptoms, radiologic findings of Behçet disease show characteristic features of its involvement in the gastrointestinal, neurologic, cardiovascular, and thoracic organ systems. In the gastrointestinal tract, Behçet disease may produce various types of ulcers in the esophagus, stomach, and small and large intestines, as well as deeply penetrating ulcerations in the ileocecal region, with frequently accompanying enteric fistulas. Neurologic involvement includes typical and atypical parenchymal neurobehcet disease, dural sinus thrombosis, cerebral arterial aneurysm, occlusion, dissection, and meningitis. Vascular involvement is divided into three subsets including venous occlusion, arterial occlusion, and arterial aneurysm. Cardiac manifestations include intracardiac thrombus, endomyocardial fibrosis, periaortic pseudoaneurysm, and rupture of the sinus of Valsalva. Manifestations of Behçet disease in the thorax include pulmonary arterial aneurysm, pulmonary arterial thromboembolism, thrombosis in the superior vena cava, pulmonary infarction, hemorrhage, and vasculitis of the pleura and pericardium. These various manifestations of Behçet disease respond to steroid treatment; however, one of the characteristics of Behçet disease is the high rate of complications and recurrence after surgery. Familiarity with its various radiologic and clinical characteristics is essential in making an accurate early diagnosis and for prompt treatment of patients with Behçet disease.

Texture-based quantification of pulmonary emphysema on high-resolution computed tomography: comparison with density-based quantification and correlation with pulmonary function test.

Purpose:To develop a system for texture-based quantification of emphysema on high-resolution computed tomography (HRCT) and to compare it with density-based quantification in correlation with pulmonary function test (PFT). Materials and Methods:Two hundred sixty-one circular regions of interest (ROI) with 16-pixel diameter [66 ROIs representing typical area of normal lung; 69 representing bronchiolitis obliterans (BO); 64, mild emphysema (ME); and 62, severe emphysema (SE)] were used to train the automated classification system based on the Support Vector Machine classifier and on variable texture and shape features. An automated quantification system was developed with a moving ROI in the lung area, which classified each pixel into 4 categories. To validate the system, the HRCT and standard-kernel-reconstructed volumetric CT data of 39 consecutive patients with emphysema were included. Using this system, the whole lung area was evaluated, and the area fractions of each class were calculated (normal lung%, BO%, ME%, SE%, respectively). The emphysema index (EI) of texture-based quantification was defined as follows: (0.3 × ME% + SE%) (TEI). EIs from density-based quantification with a threshold of −950 Hounsfield Units, were measured on both HRCT (DEI_HR_2D) and on volumetric CT (DEI_standard_3D). The agreement between TEI, DEI_HR_2D, and DEI_standard_3D was assessed using interclass correlation coefficients (ICC). Correlation of the results on the TEI with the PFT results was compared with the results of the DEI_standard_3D and the DEI_HR_2D with Spearmans correlation test. To evaluate the contribution of each texture-based quantification lesion (BO%, ME%, SE%) on PFT, multiple linear regression analysis was performed. Results:The calculated TEI (19.71% ± 17.98%) was well correlated with the DEI_standard_3D (19.42% ± 14.30%) (ICC = 0.95), whereas the ICC with DEI_HR_2D (37.22% ± 9.42%) was 0.43. TEI showed better correlation with PFT than DEI_standard_3D or DEI_HR_2D did [R = 0.71 vs. 0.67 vs. 0.61 for forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC); 0.54 vs. 0.50 vs. 0.43 for diffusing capacity (DLco), respectively]. Multiple linear regression analysis revealed that the BO% and SE% areas were independent determinants of FEV1/FVC, whereas the ME% and the SE% were determinants of DLco. Conclusion:Texture-based quantification of emphysema using an automated system showed better correlation with the PFT results than density-based quantification. Separate quantification of the BO, ME, and SE areas showed a different contribution of each component to the FEV1/FVC and the DLco. The proposed system can be successfully used for detailed regional and global evaluation of lung lesions on HRCT scanning for emphysema.

Xenon ventilation imaging using dual-energy computed tomography in asthmatics: initial experience.

Purpose:To assess the feasibility of xenon ventilation computed tomography (CT) for evaluating ventilation abnormality in asthmatics. Materials and Methods:Twenty-two, stable asthmatics (M:F = 10:12; mean age, 57.6) were included. Single-phase, whole-thorax, dual-energy CT was performed using dual-source CT (Somatom Definition, Siemens) after subjects had inhaled 30% xenon for 90 seconds. Parameters include 512 × 512 matrix; 14 × 1.2 mm collimation; 40/140 eff. mAs at 140/80 kV; 0.45 pitch; and 0.33 seconds rotation time. On the color-coded xenon map, the extent of the ventilation defect was visually assessed using a 5-point scale in each lobe (0, absent defect; 1, 0%–25%; 2, 25%–50%; 3, 50%–75%; and 4, 75%–100%), which was defined as defect score. On the weighted average image, airway wall dimensions were measured at 4 segmental bronchi in both upper and lower lobes. Patients were classified into a defect group and a defect-free group based on the presence of defects shown on the xenon map. Pulmonary function test parameters and airway wall dimensions were compared in those 2 groups. Correlation analyses between the defect score, pulmonary function test, and airway wall dimensions were performed. Results:Sixteen asthmatics showed peripheral ventilation defects on the xenon map (defect score, 6.6 ± 4.2). The defect group had a significantly lower forced expiratory volume in 1 second (FEV1) and thicker airway wall than that of the defect-free group (P = 0.04 and 0.02, respectively). The defect score correlated negatively with a ratio of FEV1 and forced vital capacity (FEV1/FVC) (r = −0.44, P = 0.04) and corrected diffusing capacity (r = −0.76, P = 0.04) and correlated positively with total lung capacity, functional residual volume, and residual volume (r = 0.90, P = 0.005; r= 0.99, P < 0.001; r = 0.88, P = 0.008, respectively). Conclusions:The ventilation defects appeared on xenon ventilation CT in asthmatics with more severe airflow limitation and airway wall thickening. The extent of the ventilation defects showed correlations with parameters of pulmonary function test.

Quantitatively assessed dynamic contrast-enhanced magnetic resonance imaging in patients with chronic obstructive pulmonary disease: correlation of perfusion parameters with pulmonary function test and quantitative computed tomography.

Objectives:The purpose of this study is to evaluate the correlation of the perfusion parameters of 3-dimensional, contrast-enhanced magnetic resonance (MR) imaging (3D CEMRI) with pulmonary function test (PFT) and quantitative computed tomography (CT) parameters in patients with chronic obstructive pulmonary disease (COPD). Materials and Methods:In 14 patients with COPD, 3D CEMRI was performed. From the signal intensity-time curves, pulmonary blood flow (PBF), pulmonary blood volume (PBV), and mean transit time of each pixel was calculated. From the volumetric CT data, the quantitative parameters including the volume fraction of the lung below −950 Housefield Units (V−950) and mean lung density were assessed. The correlation between the MR perfusion parameters and the parameters from quantitative CT and PFT was assessed using Spearman correlation analysis. The correspondence of the regional impairment of perfusion on MR perfusion maps to the areas of emphysema on quantitative CT maps in each patient was assessed qualitatively using a 4-class visual scoring method by 2 readers. Results:All 3D CEMRI examinations were successfully completed and MR perfusion parameters were obtained in all patients. The Spearman correlation test showed that PBF positively correlated with forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) (R = 0.49, P = 0.044), PBV positively correlated with FEV1/FVC (R = 0.69, P = 0.006) and negatively correlated with V−950 (R = −0.61, P = 0.020), and mean transit time positively correlated with FEV1 (R = 0.63, P = 0.017) and FEV1/FVC (R = 0.76, P = 0.002). The areas of perfusion impairment on PBF and PBV maps were relatively well correlated with the areas of emphysema on CT maps [very good or good: PBF 71.5% (reader 1) and 64.3% (reader 2) of the patients, &kgr; = 0.47 (P < 0.001); PBV 78.6% (reader 1) and 78.6% (reader 2) of the patients, &kgr; = 0.89 (P < 0.001)]. Conclusions:This study shows that the deterioration of perfusion parameters measured on MR in patients with COPD, correlates with worsening of airflow limitation on PFT and emphysema index on CT. Regional heterogeneity of emphysema on CT matches with the decreased perfusion on MR.

Dual-energy computed tomography characterization of solitary pulmonary nodules.

For the assessment of solitary pulmonary nodules (SPNs), a chest computed tomography (CT) is often performed as a combination of a nonenhanced and an enhanced scan. A nonenhanced scan is used for the detection of calcification in the SPN or lymph node, as the presence of calcification is one of the important determinants of benignity. An enhanced scan is informative in providing the degree and pattern of enhancement. In particular, the degree of enhancement of an SPN after iodine injection has been shown to be helpful in distinguishing malignant from benign nodules. Recently introduced dual-energy applications of dual-source CT simultaneously provide a virtual nonenhanced and an iodine-enhanced image from a single scan, after the administration of iodine contrast material. Therefore, a single enhanced dual-energy CT scan allows both measurement of the degree of enhancement and detection of calcifications. It may reduce radiation exposure to patients by avoiding baseline nonenhanced scans and may also reduce measurement error due to different regions of interest during the subtraction of a nonenhanced image from an enhanced image. This technique may have applications in contrast-enhanced dynamic CT and perfusion CT for the differentiation between benign and malignant lesions and the assessment of tumor angiogenesis. In this review article, we sought to address the usefulness of dual-energy CT for the assessment of SPN. In addition, we briefly review the physical principles of dual-energy CT and discuss potential future applications in patients with lung nodules.

Evaluation of computer-aided detection and dual energy software in detection of peripheral pulmonary embolism on dual-energy pulmonary CT angiography

PurposeTo evaluate the sensitivity of computer-aided detection(CAD) and dual-energy software(‘Lung PBV’, ‘Lung Vessels’) for detecting peripheral pulmonary embolism(PE).Materials and methodsBetween Jan-2007 and Jan-2008, 309 patients underwent dual-energy CT angiography(DECTA) for the evaluation of suspected PE. Among them, 37 patients were retrospectively selected; 21 with PE at segmental-or-below levels and 16 without PE according to clinical reports. A standard computer assisted detection (CAD) package and two new types of software(‘Lung PBV’, ‘Lung Vessels’) were applied on a dedicated workstation. This resulted in four alternative tests for detecting PE: DECTA alone and DECTA with CAD, ‘Lung Vessels’ and ‘Lung PBV’. Two radiologists independently read all cases at different reading sessions. Two thoracic radiologists set the reference standard by combining all information from DECTA and software. The sensitivity of detection for all, segmental and subsegmental-or-below PE were assessed.ResultsThe reference standard contained 136 PE(segmental 65, subsegmental-or-below 71). With DECTA alone, the sensitivity of detection for all, segmental and subsegmental-or-below pulmonary arteries was 54.5%/73.7%/34.4%; DECTA with CAD, 57.8%/76.8%/37.9%; DECTA with ‘Lung PBV’, 61.1%/79.9%/41.4%; DECTA with ‘Lung Vessels’, 64.0%/78.3%/48.5% respectively.ConclusionThe use of CAD, Lung Vessels and Lung PBV shows improved capability to detect peripheral PE.

Xenon ventilation CT using a dual-source dual-energy technique: dynamic ventilation abnormality in a child with bronchial atresia

Xenon ventilation CT using a dual-source dual-energy technique is a promising functional imaging method for the lung. We report the typical ventilation abnormalities, collateral ventilation and air trapping in the affected lung segment demonstrated on xenon ventilation CT in a child with bronchial atresia.