Clinical Focus

  • Diagnostic Radiology

Academic Appointments

  • Professor - Med Center Line, Radiology

Administrative Appointments

  • Associate Chair, Stanford University School of Medicine - Radiology (2004 - Present)

Professional Education

  • Internship:St Michaels Hospital (1987) Canada
  • Residency:The University of British Columbia (1992) Canada
  • Fellowship:L'Hopital Pitie-Salpetrieoe (1993) France
  • Medical Education:The University of British Columbia (1986) Canada
  • Board Certification: Diagnostic Radiology, American Board of Radiology (1992)
  • Board Certification: Diagnostic Radiology, Royal College of Physicians and Surgeons of Canada (1992)
  • BSc, McGill University, Biochemistry (1982)

Research & Scholarship

Current Research and Scholarly Interests

High-resolution computed tomography of the thorax,, particularly its application in the setting of acute lung disease in the immunocompromised host; quantitative assessment of abnormalities, using spiral CT; and enhancement characteristics of lung cancers on, CT and MRI

Clinical Trials

  • Pulmonary Interstitial Lymphography in Early Stage Lung Cancer Not Recruiting

    Non-small cell lung cancer (NSCLC) is the most deadly cancer in the world. NSCLC annually causes 150,000 deaths in the US and greater than 1 million worldwide. The standard treatment for early stage NSCLC is lobectomy with lymphadenectomy. However, many patients are poor operative candidates or decline surgery. An emerging alternative is Stereotactic Body Radiation Therapy (SBRT). Mounting evidence from Phase I/II studies demonstrates that SBRT offers excellent local control. Most SBRT trials focused on small, peripheral tumors in inoperable patients. Increasingly, clinical trials study SBRT in operable patients, often with larger, central tumors. Using clinical staging, a significant proportion of patients harbor occult nodal metastases when undergoing SBRT to the primary tumor alone. Subgroups of patients carry even higher risk of nodal metastases. These nodal metastases frequently would be removed by surgical intervention. However, SBRT, at present, is only directed at the primary tumor, potentially leading to regional failures in otherwise curable patients. To increase the effectiveness of SBRT for lung tumors, the next logical step is to explore whether the highest risk areas of disease spread can be identified and targeted. Regional failure could be reduced and outcome improved in a significant proportion of patients treated with SBRT if the primary nodal drainage (PND) were identified, targeted and treated in addition to the primary tumor. We propose to conduct a study to determine how well water soluble iodinated contrast material when injected directly into the tumor can be visualized on CT scan and integrated into radiation therapy treatment planning.

    Stanford is currently not accepting patients for this trial. For more information, please contact Laura Gable, (650) 736 - 0798.

    View full details


2014-15 Courses


Journal Articles

  • Lung Volume Reduction After Stereotactic Ablative Radiation Therapy of Lung Tumors: Potential Application to Emphysema INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS Binkley, M. S., Shrager, J. B., Leung, A. N., Popat, R., Trakul, N., Atwood, T. F., Chaudhuri, A., Maxim, P. G., Diehn, M., Loo, B. W. 2014; 90 (1): 216-223
  • Professionalism in radiology. Journal of thoracic imaging Leung, A. N. 2014; 29 (5): 284-288


    Professionalism has been described as the "basis of medicine's contract with society." This article reviews the foundational principles of medical professionalism and, more specifically, defines the nature and scope of radiologists' responsibilities to patients. In the face of ongoing changes in the environment of medical practice, maintenance of professionalism is an adaptive challenge that will require successful practitioners to be open to and actively engaged in continuous learning and self-improvement. Imaging 3.0 is a change process developed by the American College of Radiology to help radiologists redefine and reprioritize their professional activities as the discipline transitions from a volume-based to value-based specialty.

    View details for DOI 10.1097/RTI.0000000000000100

    View details for PubMedID 25160596

  • Prognostic importance of volumetric measurements in stage I lung adenocarcinoma. Radiology Yanagawa, M., Tanaka, Y., Leung, A. N., Morii, E., Kusumoto, M., Watanabe, S., Watanabe, H., Inoue, M., Okumura, M., Gyobu, T., Ueda, K., Honda, O., Sumikawa, H., Johkoh, T., Tomiyama, N. 2014; 272 (2): 557-567


    Purpose To perform volumetric analysis of stage I lung adenocarcinomas by using an automated computer program and to determine value of volumetric computed tomographic (CT) measurements associated with prognostic factors and outcome. Materials and Methods Consecutive patients (n = 145) with stage I lung adenocarcinoma who underwent surgery after preoperative chest CT were enrolled. By using volumetric automated computer-assisted analytic program, nodules were classified into three subgroups: pure ground glass, part solid, or solid. Total tumor volume, solid tumor volume, and percentage of solid volume of each cancer were calculated after eliminating vessel components. One radiologist measured the longest diameter of the solid tumor component and of total tumor with their ratio, which was defined as solid proportion. The value of these quantitative data by examining associations with pathologic prognostic factors and outcome measures (disease-free survival and overall survival) were analyzed with logistic regression and Cox proportional hazards regression models, respectively. Significant parameters identified at univariate analysis were included in the multiple analyses. Results All 22 recurrences occurred in patients with nodules classified as part solid or solid. Multiple logistic regression analysis revealed that percentage of solid volume of 63% or greater was an independent indicator associated with pleural invasion (P = .01). Multiple Cox proportional hazards regression analysis revealed that percentage of solid volume of 63% or greater was a significant indicator of lower disease-free survival (hazard ratio, 18.45 [95% confidence interval: 4.34, 78.49]; P < .001). Both solid tumor volume of 1.5 cm(3) or greater and percentage of solid volume of 63% or greater were significant indicators of decreased overall survival (hazard ratio, 5.92 and 9.60, respectively [95% confidence interval: 1.17, 30.33 and 1.17, 78.91, respectively]; P = .034 and .036, respectively). Conclusion Two volumetric measurements (solid volume, ≥1.5 cm(3); percentage of solid volume, ≥63%) were found to be independent indicators associated with increased likelihood of recurrence and/or death in patients with stage I adenocarcinoma. © RSNA, 2014.

    View details for DOI 10.1148/radiol.14131903

    View details for PubMedID 24708191

  • Ultra-low-dose CT of the Lung: Effect of Iterative Reconstruction Techniques on Image Quality ACADEMIC RADIOLOGY Yanagawa, M., Gyobu, T., Leung, A. N., Kawai, M., Kawata, Y., Sumikawa, H., Honda, O., Tomiyama, N. 2014; 21 (6): 695-703


    To compare quality of ultra-low-dose thin-section computed tomography (CT) images of the lung reconstructed using model-based iterative reconstruction (MBIR) and adaptive statistical iterative reconstruction (ASIR) to filtered back projection (FBP) and to determine the minimum tube current-time product on MBIR images by comparing to standard-dose FBP images.Ten cadaveric lungs were scanned using 120 kVp and four different tube current-time products (8, 16, 32, and 80 mAs). Thin-section images were reconstructed using MBIR, three ASIR blends (30%, 60%, and 90%), and FBP. Using the 8-mAs data, side-to-side comparison of the four iterative reconstruction image sets to FBP was performed by two independent observers who evaluated normal and abnormal findings, subjective image noise, streak artifact, and overall image quality. Image noise was also measured quantitatively. Subsequently, 8-, 16-, and 32-mAs MBIR images were compared to standard-dose FBP images. Comparisons of image sets were analyzed using the Wilcoxon signed rank test with Bonferroni correction.At 8 mAs, MBIR images were significantly better (P < .005) than other reconstruction techniques except in evaluation of interlobular septal thickening. Each set of low-dose MBIR images had significantly lower (P < .001) subjective and objective noise and streak artifacts than standard-dose FBP images. Conspicuity and visibility of normal and abnormal findings were not significantly different between 16-mAs MBIR and 80-mAs FBP images except in identification of intralobular reticular opacities.MBIR imaging shows higher overall quality with lower noise and streak artifacts than ASIR or FBP imaging, resulting in nearly 80% dose reduction without any degradations of overall image quality.

    View details for DOI 10.1016/j.acra.2014.01.023

    View details for Web of Science ID 000336414100001

  • CT patterns of fungal pulmonary infections of the lung: Comparison of standard-dose and simulated low-dose CT EUROPEAN JOURNAL OF RADIOLOGY Christe, A., Lin, M. C., Yen, A. C., Hallett, R. L., Roychoudhury, K., Schmitzberger, F., Fleischmann, D., Leung, A. N., Rubin, G. D., Vock, P., Roos, J. E. 2012; 81 (10): 2860-2866


    To assess the effect of radiation dose reduction on the appearance and visual quantification of specific CT patterns of fungal infection in immuno-compromised patients.Raw data of thoracic CT scans (64 × 0.75 mm, 120 kVp, 300 reference mAs) from 41 consecutive patients with clinical suspicion of pulmonary fungal infection were collected. In 32 patients fungal infection could be proven (median age of 55.5 years, range 35-83). A total of 267 cuboids showing CT patterns of fungal infection and 27 cubes having no disease were reconstructed at the original and 6 simulated tube currents of 100, 40, 30, 20, 10, and 5 reference mAs. Eight specific fungal CT patterns were analyzed by three radiologists: 76 ground glass opacities, 42 ground glass nodules, 51 mixed, part solid, part ground glass nodules, 36 solid nodules, 5 lobulated nodules, 6 spiculated nodules, 14 cavitary nodules, and 37 foci of air-space disease. The standard of reference was a consensus subjective interpretation by experts whom were not readers in the study.The mean sensitivity and standard deviation for detecting pathological cuboids/disease using standard dose CT was 0.91 ± 0.07. Decreasing dose did not affect sensitivity significantly until the lowest dose level of 5 mAs (0.87 ± 0.10, p=0.012). Nodular pattern discrimination was impaired below the dose level of 30 reference mAs: specificity for fungal 'mixed nodules' decreased significantly at 20, 10 and 5 reference mAs (p<0.05). At lower dose levels, classification drifted from 'solid' to 'mixed nodule', although no lesion was missed.Our simulation data suggest that tube current levels can be reduced from 300 to 30 reference mAs without impairing the diagnostic information of specific CT patterns of pulmonary fungal infections.

    View details for DOI 10.1016/j.ejrad.2011.06.059

    View details for Web of Science ID 000308079700067

    View details for PubMedID 21835569

  • Non-Small Cell Lung Cancer: Identifying Prognostic Imaging Biomarkers by Leveraging Public Gene Expression Microarray Data-Methods and Preliminary Results RADIOLOGY Gevaert, O., Xu, J., Hoang, C. D., Leung, A. N., Xu, Y., Quon, A., Rubin, D. L., Napel, S., Plevritis, S. K. 2012; 264 (2): 387-396


    To identify prognostic imaging biomarkers in non-small cell lung cancer (NSCLC) by means of a radiogenomics strategy that integrates gene expression and medical images in patients for whom survival outcomes are not available by leveraging survival data in public gene expression data sets.A radiogenomics strategy for associating image features with clusters of coexpressed genes (metagenes) was defined. First, a radiogenomics correlation map is created for a pairwise association between image features and metagenes. Next, predictive models of metagenes are built in terms of image features by using sparse linear regression. Similarly, predictive models of image features are built in terms of metagenes. Finally, the prognostic significance of the predicted image features are evaluated in a public gene expression data set with survival outcomes. This radiogenomics strategy was applied to a cohort of 26 patients with NSCLC for whom gene expression and 180 image features from computed tomography (CT) and positron emission tomography (PET)/CT were available.There were 243 statistically significant pairwise correlations between image features and metagenes of NSCLC. Metagenes were predicted in terms of image features with an accuracy of 59%-83%. One hundred fourteen of 180 CT image features and the PET standardized uptake value were predicted in terms of metagenes with an accuracy of 65%-86%. When the predicted image features were mapped to a public gene expression data set with survival outcomes, tumor size, edge shape, and sharpness ranked highest for prognostic significance.This radiogenomics strategy for identifying imaging biomarkers may enable a more rapid evaluation of novel imaging modalities, thereby accelerating their translation to personalized medicine.

    View details for DOI 10.1148/radiol.12111607

    View details for Web of Science ID 000306660000010

    View details for PubMedID 22723499

  • Lung Cancer Screening JOURNAL OF THE NATIONAL COMPREHENSIVE CANCER NETWORK Wood, D. E., Eapen, G. A., Ettinger, D. S., Hou, L., Jackman, D., Kazerooni, E., Klippenstein, D., Lackner, R. P., Leard, L., Leung, A. N., Massion, P. P., Meyers, B. F., Munden, R. F., Otterson, G. A., Peairs, K., Pipavath, S., Pratt-Pozo, C., Reddy, C., Reid, M. E., Rotter, A. J., Schabath, M. B., Sequist, L. V., Tong, B. C., Travis, W. D., Unger, M., Yang, S. C. 2012; 10 (2): 240-265

    View details for Web of Science ID 000300067400008

    View details for PubMedID 22308518

  • Case 166: Metastatic Left Pulmonary Artery Sarcoma RADIOLOGY Mittra, E. S., Iagaru, A. H., Leung, A. N. 2011; 258 (2): 645-648

    View details for DOI 10.1148/radiol.10082169

    View details for Web of Science ID 000286653700037

    View details for PubMedID 21273527

  • Yield of diagnostic procedures for invasive fungal infections in neutropenic febrile patients with chest computed tomography abnormalities MYCOSES Ho, D. Y., Lin, M., Schaenman, J., Rosso, F., Leung, A. N., Coutre, S. E., Sista, R. R., Montoya, J. G. 2011; 54 (1): 59-70


    Haematological patients with neutropenic fever are frequently evaluated with chest computed tomography (CT) to rule out invasive fungal infections (IFI). We retrospectively analysed data from 100 consecutive patients with neutropenic fever and abnormal chest CT from 1998 to 2005 to evaluate their chest CT findings and the yield of diagnostic approaches employed. For their initial CTs, 79% had nodular opacities, with 24.1% associated with the halo sign. Other common CT abnormalities included pleural effusions (48%), ground glass opacities (37%) and consolidation (31%). The CT findings led to a change in antifungal therapy in 54% of the patients. Fifty-six patients received diagnostic procedures, including 46 bronchoscopies, 25 lung biopsies and seven sinus biopsies, with a diagnostic yield for IFI of 12.8%, 35.0% and 83.3%, respectively. In conclusion, chest CT plays an important role in the evaluation of haematological patients with febrile neutropenia and often leads to a change in antimicrobial therapy. Pulmonary nodules are the most common radiological abnormality. Sinus or lung biopsies have a high-diagnostic yield for IFI as compared to bronchoscopy. Patients with IFI may not have sinus/chest symptoms, and thus, clinicians should have a low threshold for performing sinus/chest imaging, and if indicated and safe, a biopsy of the abnormal areas.

    View details for DOI 10.1111/j.1439-0507.2009.01760.x

    View details for Web of Science ID 000284900600009

    View details for PubMedID 19793207

  • Epoprostenol-associated pneumonitis: Diagnostic use of a T-cell proliferation assay JOURNAL OF HEART AND LUNG TRANSPLANTATION Kudelko, K. T., Nadeau, K., Leung, A. N., Liu, J., Haddad, F., Zamanian, R. T., Perez, V. D. 2010; 29 (9): 1071-1075


    We describe a case of severe drug-induced interstitial pneumonitis in a woman with idiopathic pulmonary arterial hypertension receiving epoprostenol confirmed by a drug T-cell proliferation assay. Proliferation assays were completed in our patient and in a healthy control. Isolated T cells were incubated with CD3-depleted peripheral blood mononuclear cells and then stimulated to proliferate with (3)H-thymidine in the presence of epoprostenol, other prostanoid analogs, and controls. A significant (p < 0.001) T-cell proliferation response occurred in our patient in the presence of epoprostenol alone. There was a trend towards an increased T-cell response to treprostinil but this was statistically insignificant. There was no significant T-cell response to the diluent alone, normal saline, iloprost, or alprostadil. There was no significant proliferation to any drug in the healthy control. Hence, a drug T-cell proliferation assay confirmed that epoprostenol can rarely incite a profound inflammatory response in the pulmonary interstitium.

    View details for DOI 10.1016/j.healun.2010.04.023

    View details for Web of Science ID 000281494800016

  • Computer-aided detection (CAD) of lung nodules in CT scans: radiologist performance and reading time with incremental CAD assistance EUROPEAN RADIOLOGY Roos, J. E., Paik, D., Olsen, D., Liu, E. G., Chow, L. C., Leung, A. N., Mindelzun, R., Choudhury, K. R., Naidich, D. P., Napel, S., Rubin, G. D. 2010; 20 (3): 549-557


    The diagnostic performance of radiologists using incremental CAD assistance for lung nodule detection on CT and their temporal variation in performance during CAD evaluation was assessed.CAD was applied to 20 chest multidetector-row computed tomography (MDCT) scans containing 190 non-calcified > or =3-mm nodules. After free search, three radiologists independently evaluated a maximum of up to 50 CAD detections/patient. Multiple free-response ROC curves were generated for free search and successive CAD evaluation, by incrementally adding CAD detections one at a time to the radiologists' performance.The sensitivity for free search was 53% (range, 44%-59%) at 1.15 false positives (FP)/patient and increased with CAD to 69% (range, 59-82%) at 1.45 FP/patient. CAD evaluation initially resulted in a sharp rise in sensitivity of 14% with a minimal increase in FP over a time period of 100 s, followed by flattening of the sensitivity increase to only 2%. This transition resulted from a greater prevalence of true positive (TP) versus FP detections at early CAD evaluation and not by a temporal change in readers' performance. The time spent for TP (9.5 s +/- 4.5 s) and false negative (FN) (8.4 s +/- 6.7 s) detections was similar; FP decisions took two- to three-times longer (14.4 s +/- 8.7 s) than true negative (TN) decisions (4.7 s +/- 1.3 s).When CAD output is ordered by CAD score, an initial period of rapid performance improvement slows significantly over time because of non-uniformity in the distribution of TP CAD output and not to a changing reader performance over time.

    View details for DOI 10.1007/s00330-009-1596-y

    View details for Web of Science ID 000274544800005

    View details for PubMedID 19760237

  • Best Cases from the AFIP Fatal 2009 Influenza A (H1N1) Infection, Complicated by Acute Respiratory Distress Syndrome and Pulmonary Interstitial Emphysema RADIOGRAPHICS Guo, H. H., Sweeney, R. T., Regula, D., Leung, A. N. 2010; 30 (2): 327-333

    View details for DOI 10.1148/rg.302095213

    View details for Web of Science ID 000275622400003

    View details for PubMedID 20068001

  • Cystic Fibrosis HRCT Scores Correlate Strongly With Pseudomonas Infection PEDIATRIC PULMONOLOGY Robinson, T. E., Leung, A. N., Chen, X., Moss, R. B., Emond, M. J. 2009; 44 (11): 1107-1117


    In order to establish a valid surrogate outcome measure, it must be shown that the outcome measure (chest HRCT scores in cystic fibrosis [CF] patients) demonstrates strong statistical association with established endpoints of disease, such as Pseudomonas aeruginosa (Pa) airway acquisition, acute exacerbations, or mortality.We estimated and tested the association between Pa infection status (Pa+ vs. Pa-) and baseline chest HRCT scores in 25 children with mild-to-moderate CF lung disease. For comparison, we estimated the association between Pa status and pulmonary function tests (PFTs), chest X-rays (CXR) scores, and BMI. Pa acquisition was determined from respiratory culture results and systematic review of clinic notes.All subjects had respiratory cultures performed prior to or at baseline with a median of 19 months of retrospective culture observation (SD = 15.7 months, range: 0-52.5 months). The difference between age-adjusted mean total HRCT score for Pa+ versus Pa- was highly significant (P < 0.00001) with a near-perfect separation between scores in Pa+ versus Pa- patients. Similar results were found for several HRCT sub-scores. Among PFTs, only residual volume-to-total lung capacity (RV/TLC) had a significant difference between group means (P = 0.03), but the overlap between groups in RV/TLC measurements was large.CF HRCT scores correlate highly with Pa acquisition, a clinically meaningful measure of progressing CF lung disease. HRCT scores are highly sensitive at predicting Pa acquisition status, while most PFT measures, chest radiograph (CXR) scores, and body mass index are not. These results provide further evidence that HRCT is appropriate for use in patient care and as an outcome measure in clinical trials.

    View details for DOI 10.1002/ppul.21107

    View details for Web of Science ID 000271602200009

    View details for PubMedID 19824046

  • Discordance rates between preliminary and final radiology reports on cross-sectional imaging studies at a level 1 trauma center ACADEMIC RADIOLOGY Stevens, K. J., Griffiths, K. L., Rosenberg, J., Mahadevan, S., Zatz, L. M., Leung, A. N. 2008; 15 (10): 1217-1226


    The goal was to determine discordance rates between preliminary radiology reports provided by on-call radiology house staff and final reports from attending radiologists on cross-sectional imaging studies requested by emergency department staff after hours.A triplicate carbon copy reporting form was developed to provide permanent records of preliminary radiology reports and to facilitate communication of discrepant results to the emergency department. Data were collected over 21 weeks to determine the number of discordant readings. Patients' medical records were reviewed to show whether discrepancies were significant or insignificant and to assess their impact on subsequent management and patient outcome.The emergency department requested 2830 cross-sectional imaging studies after hours and 2311 (82%) had a copy of the triplicate form stored in radiology archives. Discrepancies between the preliminary and final report were recorded in 47 (2.0%), with 37 (1.6%) considered significant: 14 patients needed no change, 13 needed a minor change, and 10 needed a major change in subsequent management. Ten (0.43%) of the discordant scans were considered insignificant. A random sample of 104 (20%) of the 519 scans without a paper triplicate form was examined. Seventy-one (68%) did have a scanned copy of the triplicate form in the electronic record, with a discrepancy recorded in 3 (4.2%), which was not statistically different from the main cohort (P = .18).Our study suggests a high level of concordance between preliminary reports from on-call radiology house staff and final reports by attending subspecialty radiologists on cross-sectional imaging studies requested by the emergency department.

    View details for DOI 10.1016/j.acra.2008.03.017

    View details for Web of Science ID 000259742400002

    View details for PubMedID 18790392

  • Primary interpretation of thoracic MDCT images using coronal reformations AMERICAN JOURNAL OF ROENTGENOLOGY Kwan, S. W., Partik, B. L., Zinck, S. E., Chan, F. P., Kee, S. T., Leung, A. N., Voracek, M., Rubin, G. D. 2005; 185 (6): 1500-1508


    The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images.Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test.The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively).Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.

    View details for DOI 10.2214/AJR.04.1335

    View details for Web of Science ID 000233510600019

    View details for PubMedID 16304004

  • Recurrent lymphoma of the lung - Computed tomography appearance JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY Hwang, G. L., Leung, A. N., Zinck, S. E., Berry, G. J. 2005; 29 (2): 228-230


    To describe the computed tomography findings of recurrent lymphoma involving the lung.Computed tomography scans of 15 patients with biopsy-proven recurrent lymphoma involving the lung were reviewed. Group mean age of enrolled patients was 38 years (range: 14-68 years). Pathologic specimens were obtained by thoracoscopic or open wedge biopsy (n = 8), transbronchial biopsy (n = 5), and fine needle aspiration (n = 2).Nodules, the most common manifestation, were present in all patients; nodules were greater than 10 in number in 12 (80%) of 15 cases and predominantly 6-10 mm in size in 8 cases (53%). Nodular distribution was bilateral and multilobar except in 2 patients, in whom a solitary pulmonary nodule was found. Lymphadenopathy was the second most common finding; it was seen in 13 (87%) of 15 cases and involved an average of 5 nodal stations.Recurrent lymphoma in the lung most commonly manifests as multiple pulmonary nodules that are typically bilateral and multilobar in distribution.

    View details for Web of Science ID 000228030400014

    View details for PubMedID 15772542

  • Pulmonary nodules on multi-detector row CT scans: Performance comparison of radiologists and computer-aided detection RADIOLOGY Rubin, G. D., Lyo, J. K., Paik, D. S., Sherbondy, A. J., Chow, L. C., Leung, A. N., Mindelzun, R., Schraedley-Desmond, P. K., Zinck, S. E., Naidich, D. P., Napel, S. 2005; 234 (1): 274-283


    To compare the performance of radiologists and of a computer-aided detection (CAD) algorithm for pulmonary nodule detection on thin-section thoracic computed tomographic (CT) scans.The study was approved by the institutional review board. The requirement of informed consent was waived. Twenty outpatients (age range, 15-91 years; mean, 64 years) were examined with chest CT (multi-detector row scanner, four detector rows, 1.25-mm section thickness, and 0.6-mm interval) for pulmonary nodules. Three radiologists independently analyzed CT scans, recorded the locus of each nodule candidate, and assigned each a confidence score. A CAD algorithm with parameters chosen by using cross validation was applied to the 20 scans. The reference standard was established by two experienced thoracic radiologists in consensus, with blind review of all nodule candidates and free search for additional nodules at a dedicated workstation for three-dimensional image analysis. True-positive (TP) and false-positive (FP) results and confidence levels were used to generate free-response receiver operating characteristic (ROC) plots. Double-reading performance was determined on the basis of TP detections by either reader.The 20 scans showed 195 noncalcified nodules with a diameter of 3 mm or more (reference reading). Area under the alternative free-response ROC curve was 0.54, 0.48, 0.55, and 0.36 for CAD and readers 1-3, respectively. Differences between reader 3 and CAD and between readers 2 and 3 were significant (P < .05); those between CAD and readers 1 and 2 were not significant. Mean sensitivity for individual readings was 50% (range, 41%-60%); double reading resulted in increase to 63% (range, 56%-67%). With CAD used at a threshold allowing only three FP detections per CT scan, mean sensitivity was increased to 76% (range, 73%-78%). CAD complemented individual readers by detecting additional nodules more effectively than did a second reader; CAD-reader weighted kappa values were significantly lower than reader-reader weighted kappa values (Wilcoxon rank sum test, P < .05).With CAD used at a level allowing only three FP detections per CT scan, sensitivity was substantially higher than with conventional double reading.

    View details for DOI 10.1148/radiol.2341040589

    View details for Web of Science ID 000225864800038

    View details for PubMedID 15537839

  • Case 63: hepatopulmonary syndrome. Radiology Leung, A. N. 2003; 229 (1): 64-67

    View details for PubMedID 14519870

  • Invasive aspergillosis in the setting of cardiac transplantation CLINICAL INFECTIOUS DISEASES Montoya, J. G., Chaparro, S. V., Celis, D., Cortes, J. A., Leung, A. N., Robbins, R. C., Stevens, D. A. 2003; 37: S281-S292


    Among patients undergoing heart transplantation, Aspergillus is the opportunistic pathogen with the highest attributable mortality. The median time of onset from transplantation for invasive pulmonary aspergillosis (IPA) was 46 days, but the median time to first positive culture result was 104 days among patients with Aspergillus colonization but no invasive disease. Most patients with IPA presented with fever and cough within the first 90 days of transplantation and with single or multiple pulmonary nodules. None of the heart transplant recipients with either IPA or invasive extrapulmonary aspergillosis (IEPA) had associated neutropenia. Human leukocyte antigen A1 locus was found significantly more frequently among patients colonized with Aspergillus than among patients with IPA (P<.006) or IEPA (P<.001). Even in the absence of neutropenia, IPA should be suspected for heart transplant recipients who have fever and respiratory symptoms within the first 3 months of transplantation, have a positive result of culture of respiratory secretions, and have abnormal radiological findings (particularly nodules).

    View details for Web of Science ID 000186262900006

    View details for PubMedID 12975755

  • Composite spirometric-computed tomography outcome measure in early cystic fibrosis lung disease AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Robinson, T. E., Leung, A. N., Northway, W. H., Blankenberg, F. G., Chan, F. P., Bloch, D. A., Holmes, T. H., Moss, R. B. 2003; 168 (5): 588-593


    With the advent of therapies aimed at young patients with cystic fibrosis, who have mildly reduced pulmonary function, the need for improved outcome measures that discriminate treatment effects has become important. Pulmonary function measurements or chest high-resolution computed tomography (HRCT) scores have been separately used to assess interventions. We evaluated these modalities separately and together during a treatment study to develop a more sensitive outcome measure. In a 1-year trial, 25 children randomized either to daily Pulmozyme or to normal saline aerosol were evaluated at randomization and at 3 and 12 months. Outcome variables were pulmonary function test (PFT) results, a global HRCT score, and a composite score incorporating PFTs and HRCT scoring. Regression analyses with generalized estimating equations permitted estimation of the difference in treatment effect between groups over time for each outcome. The largest difference in treatment effects observed at 12 months, measured by the percentage change from baseline, were with the composite total and maximal CT/PFT scores (35.4 and 30.4%), compared with mean forced expiratory flow during the middle half of the FVC (FEF25-75%) (13.0%) and total and maximal global HRCT scores (6.2%, 7.2%). The composite total and maximal CT/PFT scores were the most sensitive outcome measures for discriminating a treatment effect in children with cystic fibrosis with normal or mildly reduced pulmonary function during a 1-year trial of Pulmozyme.

    View details for DOI 10.1164/rccm.200209-1093OC

    View details for Web of Science ID 000185039000015

    View details for PubMedID 12746252

  • Chronic expanding hematoma of the thorax AMERICAN JOURNAL OF ROENTGENOLOGY Hwang, G. L., Moffatt, S. D., Mitchell, J. D., Leung, A. N. 2003; 180 (4): 1182-1183

    View details for Web of Science ID 000181745500064

    View details for PubMedID 12646486

  • Using a dedicated lung-marker system for localization of pulmonary nodules before thoracoscopic surgery AMERICAN JOURNAL OF ROENTGENOLOGY Partik, B. L., Leung, A. N., Muller, M. R., Breitenseher, M., Eckersberger, F., Dekan, G., Helbich, T. H., Metz, V. 2003; 180 (3): 805-809


    Our aim was to evaluate the effectiveness of a commercially available dedicated lung-marker system for localization of pulmonary nodules before video-assisted thoracoscopic surgery.Guidewires were positioned under CT fluoroscopy guidance in 16 patients (11 men, five women; age range, 39-79 years; mean age, 60.4 years). We measured the size of the targeted nodule, its distance to the closest pleural surface, the angle between the introducer needle and the chest wall, and the time for performance of the procedure in each patient. Note was made of any complications after guidewire placement.In the 16 patients, the average nodule size was 6.7 mm (range, 3-12 mm), the average distance to the pleural surface was 10.6 mm (range, 3-22 mm), and the average pleural puncture angle was 59 degrees (range, 25-78 degrees). The marking procedure was completed within an average of 9.5 min (range, 7-15 min). Small pneumothoraces occurred in five (31.3%) of 16 patients. In 15 (93.8%) of 16 patients, thoracoscopic resection of the targeted nodule was successful; in one patient with dyspnea (6.3%), inaccurate localization resulting in an open thoracotomy occurred because an intervening fissure was not visualized. Dislodgement of the guidewire into the pleural space occurred in one patient (6.3%).The dedicated lung-marker system is a fast and effective method for localization of pulmonary nodules before thoracoscopic resection.

    View details for Web of Science ID 000181153400042

    View details for PubMedID 12591700

  • Short echo time MR spectroscopic imaging of the lung parenchyma JOURNAL OF MAGNETIC RESONANCE IMAGING Gold, G. E., Pauly, J. M., Leung, A. N., Block, W. F., Meyer, C. H., Sze, R., Macovski, A., Stark, P. 2002; 15 (6): 679-684


    To perform short echo time MR spectroscopic imaging of the lung parenchyma on normal volunteers.A short echo time projection-reconstruction spectroscopic imaging sequence was implemented on a commercial 1.5T whole body MRI scanner. Images and spectra of the lung parenchyma were obtained from five normal volunteers. Breath-held spectroscopic imaging was also performed.Spectroscopic imaging of short-T2* species allows visualization of different anatomic structures based upon their frequency shifts. A characteristic peak from the parenchyma was seen at three ppm from water frequency.Short echo time MR spectroscopic imaging of the lung parenchyma was demonstrated in normal volunteers. This method may improve proton imaging of the lungs and add specificity to the diagnosis of pulmonary disease.

    View details for DOI 10.1002/jmri.10113

    View details for Web of Science ID 000175918300008

    View details for PubMedID 12112518

  • CT of noninfectious granulomatous lung disease RADIOLOGIC CLINICS OF NORTH AMERICA Zinck, S. E., Schwartz, E., Berry, G. J., Leung, A. N. 2001; 39 (6): 1189-?


    Noninfectious granulomatous diseases of the lung consist of a diverse group of disorders that logically can be subdivided into those with and without associated vasculitis. This article reviews the epidemiologic, clinical, pathologic, and radiologic features of sarcoidosis, hypersensitivity pneumonitis, berylliosis, and the five entities traditionally classified as pulmonary angiitis and granulomatosis.

    View details for Web of Science ID 000172023200008

    View details for PubMedID 11699668

  • Cellulose granulomatosis presenting as centrilobular nodules: CT and histologic findings AMERICAN JOURNAL OF ROENTGENOLOGY Bendeck, S. E., Leung, A. N., Berry, G. J., Daniel, D., Ruoss, S. J. 2001; 177 (5): 1151-1153

    View details for Web of Science ID 000171732700034

    View details for PubMedID 11641191

  • Spirometer-triggered high-resolution computed tomography and pulmonary function measurements during an acute exacerbation in patients with cystic fibrosis JOURNAL OF PEDIATRICS Robinson, T. E., Leung, A. N., Northway, W. H., Blankenberg, F. G., Bloch, D. A., Oehlert, J. W., Al-Dabbagh, H., Hubli, S., Moss, R. B. 2001; 138 (4): 553-559


    To evaluate a high-resolution computed tomography (HRCT) scoring system, clinical parameters, and pulmonary function measurements in patients with cystic fibrosis (CF) before and after therapy for a pulmonary exacerbation.Patients (n = 17) were evaluated by spirometer-triggered HRCT imaging, clinical parameters, and pulmonary function tests (PFTs) before and after treatment. HRCT scans were reviewed by 3 radiologists using a modified Bhalla scoring system.Bronchiectasis, bronchial wall thickening, and air trapping were identified in all subjects on initial evaluation. The initial total HRCT score correlated significantly with the Brasfield score (r = -.91, P <.001) and several PFT measures. After treatment, there were improvements in the acute change clinical score (ACCS) (P <.001), most pulmonary function measurements, and total HRCT score (P <.05). Bronchiectasis, bronchial wall thickening, and air trapping did not significantly change. Mucus plugging subcomponent HRCT score, slow vital capacity (SVC), forced expiratory volume in 1 second (FEV(1)), and forced vital capacity (FVC) (percent predicted) and reversible and total HRCT scores were most sensitive to change by effect size analysis.Improvements occurred with treatment in total and reversible HRCT scores, PFTs, and ACCS. Total and reversible HRCT scores and percent predicted SVC, FEV1, and FVC were the most sensitive to change. The greatest change was seen in the mucus plugging subcomponent HRCT score.

    View details for Web of Science ID 000168175400024

    View details for PubMedID 11295720

  • Case report - Paclitaxel-induced hypersensitivity pneumonitis: Radiographic and CT findings AMERICAN JOURNAL OF ROENTGENOLOGY Wong, P., Leung, A. N., Berry, G. J., Atkins, K. A., Montoya, J. G., Ruoss, S. J., Stockdale, F. E. 2001; 176 (3): 718-720
  • Digital storage phosphor chest radiography: An ROC study of the effect of 2K versus 4K matrix size on observer performance RADIOLOGY Miro, S. P., Leung, A. N., Rubin, G. D., Choi, Y. H., Kee, S. T., Mindelzun, R. E., Stark, P., Wexler, L., Plevritis, S. K., Betts, B. J. 2001; 218 (2): 527-532


    To compare observer performance in the detection of abnormalities on 1,760 x 2,140 matrix (2K) and 3,520 x 4,280 matrix (4K) digital storage phosphor chest radiographs.One hundred sixty patients who underwent dedicated computed tomography (CT) of the thorax were prospectively recruited into the study. Posteroanterior and lateral computed radiographs of the chest were acquired in each patient and printed in 2K and 4K formats. Six radiologists independently analyzed the hard-copy images and scored the presence of parenchymal (opacities 2 cm, and subtle interstitial), mediastinal, and pleural abnormalities on a five-point confidence scale. With CT as the reference standard, observer performance tests were carried out by using receiver operating characteristic (ROC) analysis.Analysis of averaged observer performance showed 2K and 4K images were equally effective in detection of all three groups of abnormalities. In the detection of the three subtypes of parenchymal abnormalities, there were no significant differences in averaged performance between the 2K and 4K formats (area below ROC curve [A(z)] values: opacities 2 cm, 0.86 +/-.025 and 0.85 +/- 0.030; subtle interstitial abnormalities, 0.73 +/- 0.041 and 0.72 +/- 0.041). Averaged performance in detection of mediastinal and pleural abnormalities was equivalent (A(z) values: mediastinal, 0.70 +/- 0.046 and 0.73 +/- 0.033; pleural, 0.85 +/- 0.032 and 0.86 +/- 0.033).Observer performance in detection of parenchymal, mediastinal, and pleural abnormalities was not significantly different on 2K and 4K storage phosphor chest radiographs.

    View details for Web of Science ID 000166728200033

    View details for PubMedID 11161174

  • A model for faculty mentoring in academic radiology ACADEMIC RADIOLOGY Illes, J., Glover, G. H., Wexler, L., Leung, A. N., Glazer, G. M. 2000; 7 (9): 717-724


    The purpose of this report is to describe the development and implementation of a faculty mentoring program in radiology designed to promote the career development of junior faculty and enhance communication in the department.The mentoring program was implemented in five stages: organizational readiness, participant recruitment, mentor matching and orientation, implementation, and evaluation. Evaluations were based on Likert scale ratings and qualitative feedback. A retrospective analysis was also conducted of the annual performance reviews of junior faculty in the areas of research, teaching, patient care, and overall performance.An average of 83% (19 of 23) of the junior faculty participated in the pilot phase of the mentoring program. During five rounds of testing, the median rating (1 indicates not important; 10, extremely important) from responding junior faculty was 10 for overall value of individual mentoring meetings; the median rating for the mentors responding was 8.75. Research and academic development were identified as the areas of greatest importance to the faculty. Research and patient care were most improved as assessed by faculty peers during performance reviews. The schedule of semiannual formal mentoring meetings was reported to be optimal.The program was implemented to the satisfaction of junior faculty and mentors, and longitudinal performance suggests positive effects. Issues to be contended with include confidentiality and the time needed for mentoring beyond already saturated schedules. Overall, the authors propose that mentoring programs can be an asset to academic radiology departments and a key factor in maintaining their vitality.

    View details for Web of Science ID 000089143200007

    View details for PubMedID 10987334

  • A curriculum in chest radiology for diagnostic radiology residency, with goals and objectives ACADEMIC RADIOLOGY Kazerooni, E. A., Collins, J., Reddy, G. P., Nath, H. P., Batra, P. V., Boxt, L. M., Duerinckx, A. J., Erasmus, J. J., Fishman, J. E., Leung, A. N., Tarver, R. D., Wexler, L., Winer-Muram, H. T. 2000; 7 (9): 730-743

    View details for Web of Science ID 000089143200010

    View details for PubMedID 10987336

  • Aorta and iliac arteries: Single versus multiple detector-row helical CT angiography RADIOLOGY Rubin, G. D., Shiau, M. C., Leung, A. N., Kee, S. T., Logan, L. J., Sofilos, M. C. 2000; 215 (3): 670-676


    To compare single- versus four-channel helical computed tomographic (CT) aortography.Forty-eight patients with aortic aneurysm or dissection underwent four- and one-channel CT angiography. Scan pairs covered the thoracic inlet to the diaphragm (n = 10) and supraceliac abdominal aorta (n = 19) or thoracic inlet (n = 19) to the femoral arterial bifurcations. For four-channel CT, nominal section thickness and pitch were 2.5 mm and 6.0, respectively, and for one-channel CT, 3.0 mm and 2.0 to the infrarenal aorta and 5.0 mm and 2.0 to the femoral arteries. Effective section thickness, scanning duration, scanning coverage, dose of iodinated contrast material, and mean aortoiliac attenuation were compared. Data were summarized as speed (coverage/duration), scanning efficiency (speed/section thickness), and contrast efficiency (mean aortic attenuation/dose of contrast material).At four- versus one-channel CT, CT angiography was 2.6 times faster, scanning efficiency was 4.1 times greater, contrast efficiency was 2.5 times greater, dose of contrast material was reduced (mean, 57%; 97 vs 232 mL) without a significant change in aortic enhancement, and sections were thinner (mean, 40%; 3.2 vs 5.3 mm) despite a 59% shorter scanning duration (22 vs 56 seconds).Substantially reduced doses of contrast medium, shorter scanning durations, and narrower effective sections result with four- versus one-channel CT aortography. No advantages of one-channel CT aortography were demonstrated.

    View details for Web of Science ID 000087247000009

    View details for PubMedID 10831682

  • Primary bronchogenic carcinoma after heart or lung transplantation: Radiologic and clinical findings JOURNAL OF THORACIC IMAGING Choi, Y. H., Leung, A. N., Miro, S., Poirier, C., Hunt, S., Theodore, J. 2000; 15 (1): 36-40


    Chronic immunosuppression in organ transplant recipients predisposes to the development of malignant disease. The authors describe their 29-year institutional experience of bronchogenic carcinoma developing after heart and lung transplantation. Seven cases of bronchogenic carcinoma were diagnosed in 1,119 heart and lung transplant recipients. Computed tomography scans and radiographs at time of diagnosis, as well as prior radiographs available in six patients were retrospectively analyzed by two radiologists in consensus. The seven cases involved six heart and one lung transplant recipients. Six patients were smokers with a mean smoking history of 66 pack-years. Mean time interval from transplantation to cancer detection was 25 months. Radiologic findings consisted of a solitary pulmonary nodule (n = 3), mass with satellite nodules (n = 1), and obstructive pneumonitis (n = 1). In the sixth patient, the cancer was not radiographically visible because of obscuration by adjacent fibrosis. On review, radiographic abnormalities were present a mean of 12 months prior to diagnosis in 66% of patients. In the heart or lung transplant population, bronchogenic carcinoma develops in recipients with extensive smoking histories. It presents radiographically as a nodule, mass, or obstructive pneumonitis, and is usually visible on radiographs before the time of diagnosis.

    View details for Web of Science ID 000084709000008

    View details for PubMedID 10634661

  • Radiology of pneumonia CLINICS IN CHEST MEDICINE Katz, D. S., Leung, A. N. 1999; 20 (3): 549-?


    Chest radiography is the imaging technique of choice in evaluating patients with suspected pneumonia because of its low radiation dose, low cost, and wide accessibility. In daily practice, radiographs are used to confirm the clinical diagnosis of pneumonia, characterize the extent and severity of disease, search for complications such as empyema, monitor the response to therapy, and examine for possible alternative or additional diagnoses. Although CT scan has no defined role in the routine assessment of patients with either community-acquired or nosocomial pneumonias, its advantages of superior contrast resolution and cross-sectional display can often be helpful in the analysis of complex cases, particularly when radiographic evidence of associated central obstruction, cavitation, lymphadenopathy, or empyema is equivocal. In the immunocompromised patient population, high-resolution CT has been shown to be more sensitive than plain film radiography in the early detection of pulmonary infections.

    View details for Web of Science ID 000083128300008

    View details for PubMedID 10516903

  • Radiologic findings: Pulmonary infections after bone marrow transplantation JOURNAL OF THORACIC IMAGING Choi, Y. H., Leung, A. N. 1999; 14 (3): 201-206


    Pulmonary infections are a significant source of morbidity and mortality in the bone marrow transplant population. This pictorial essay reviews the typical time period and imaging findings associated with common pulmonary pathogens that affect bone marrow transplant recipients.

    View details for Web of Science ID 000081198700007

    View details for PubMedID 10404506

  • Standardized high-resolution CT of the lung using a spirometer-triggered electron beam CT scanner AMERICAN JOURNAL OF ROENTGENOLOGY Robinson, T. E., Leung, A. N., Moss, R. B., Blankenberg, F. G., Al-Dabbagh, H., Northway, W. H. 1999; 172 (6): 1636-1638

    View details for Web of Science ID 000080427900034

    View details for PubMedID 10350305

  • Pulmonary infections after bone marrow transplantation: Clinical and radiographic findings RADIOLOGY Leung, A. N., Gosselin, M. V., Napper, C. H., Braun, S. G., Hu, W. W., Wong, R. M., Gasman, J. 1999; 210 (3): 699-710


    To assess the clinical and radiographic findings of pulmonary infections diagnosed by using invasive means.Fifty-nine episodes of pulmonary infection were diagnosed in 52 (7.2%) of a consecutive series of 725 adult bone marrow transplant recipients. Causative organisms, time of diagnoses, radiographic patterns, and mortality rates were reviewed.Cytomegalovirus and Aspergillus species were the two most common pathogens, accounting for 22 and 17 episodes, respectively. During the first 30 days after bone marrow transplantation, fungi caused the majority (nine [82%] of 11 episodes) of pulmonary infections; from days 31 to 100, viruses predominated (21 [62%] of 34 episodes). Recipients of allogeneic transplants had a higher probability of developing Cytomegalovirus pneumonitis than did the recipients of autologous and syngeneic transplants (P < .001). Radiographic findings of Cytomegalovirus pneumonia consisted of parenchymal opacification (90%) and innumerable nodules smaller than 5 mm (29%); in two patients, radiographs were normal. Nodules, masses, or nodules and masses, present in nine (69%) of the 13 patients with Aspergillus infection, were the most common radiographic findings in invasive aspergillosis. Bone marrow transplant recipients with a documented pulmonary infection were found to have a lower event-free survival than recipients without infection (P < .001).Opportunistic pathogens account for the majority of pulmonary infections requiring invasive diagnosis and tend to manifest at predictable times in the course of events following recovery from bone marrow transplantation. Cytomegalovirus, the most common pathogen, causes a spectrum of radiographic findings that includes normal findings. Occurrence of a pulmonary infection is associated with an increased mortality rate.

    View details for Web of Science ID 000078796500018

    View details for PubMedID 10207470

  • Pulmonary tuberculosis: The essentials RADIOLOGY Leung, A. N. 1999; 210 (2): 307-322

    View details for Web of Science ID 000078277900003

    View details for PubMedID 10207408

  • Thoracic spiral CT: Influence of subsecond gantry rotation on image quality RADIOLOGY Rubin, G. D., Leung, A. N., Robertson, V. J., Stark, P. 1998; 208 (3): 771-776


    To determine if the lower milliampere second setting and shorter acquisition time of subsecond spiral computed tomography (CT) affects the image quality of thoracic CT scans.In 92 consecutive outpatients referred for thoracic CT, spiral CT (120 kV, 292 mA) was performed with 1-second (n = 45) or 0.75-second (n = 47) scanning time. An equal percentage of patients (70%) in each group received intravenous contrast medium. At six mediastinal and six lung zones, degradation due to motion and noise, respectively, were graded independently on a four-point scale by three blinded radiologists. Statistically significant differences were determine with a two-tailed test.Mediastinal image quality was significantly better on 0.75-second scans than on 1-seconds scans (P < .001). Regions with the greatest improvement in image quality were around the aortic root, cardiac ventricles, and aortic arch. Lung image quality was also better on 0.75-second scans than on 1-second scans (P = .04). On 0.75- and 1-second scans, respectively, motion-related artifacts were found to degrade image quality 6.2 and 8.7 times more than noise-related artifacts in the mediastinum and 2.6 and 3.9 times more in the lungs.Subsecond spiral CT is associated with improved clarity and diminished motion artifacts on mediastinal and pulmonary images when compared with 1-second spiral CT.

    View details for Web of Science ID 000075488200033

    View details for PubMedID 9722858

  • Unsuspected pulmonary embolism: Prospective detection on routine helical CT scans RADIOLOGY Gosselin, M. V., Rubin, G. D., Leung, A. N., Huang, J., Rizk, N. W. 1998; 208 (1): 209-215


    To determine the prevalence of unsuspected pulmonary embolism (PE) on routine thoracic helical computed tomographic (CT) scans and to quantify the improvement in PE detection by using a cine-paging mode on a workstation instead of hard-copy review.Seven hundred eighty-five patients referred for routine contrast medium-enhanced thoracic CT within 9 months were prospectively recruited. Helical CT was performed. Studies were prospectively interpreted by four radiologists. Two radiologists performed routine, undirected, hard-copy consensus review for official interpretation; two of three thoracic radiologists independently performed a dedicated workstation-based search for PE. The presence of PE involving the main, lobar, or segmental pulmonary arteries was assigned a score of 1-5 (1 = definitely negative, 5 = definitely positive) by each independent reviewer. Patients with a score of 4 or 5 underwent lower-extremity ultrasound, ventilation-perfusion scintigraphy, or both, followed by pulmonary CT angiography if the findings were still equivocal.Twelve (1.5%) of the 785 patients had unsuspected PE, with an inpatient prevalence of 5% (eight of 160) and an outpatient prevalence of 0.6% (four of 625). Of the 12 patients with unsuspected PE, 10 (83%) had cancer. Of the 81 inpatients with cancer, seven (9%) had unsuspected PE. A dedicated workstation-based search resulted in detection of PE in three more patients (25%) than did hard-copy interpretation.The prevalence of unsuspected PE was highest among inpatients with cancer. A directed, workstation-based search can improve the PE detection rate over that with hard-copy review.

    View details for Web of Science ID 000074296300033

    View details for PubMedID 9646815

  • Primary malignant pulmonary hemangiopericytoma CLINICAL IMAGING Katz, D. S., Lane, M. J., Leung, A. N., Marcus, F. S., Sakata, M. K. 1998; 22 (3): 192-195


    A primary malignant pulmonary hemangiopericytoma was diagnosed in a 45-year-old woman who complained of 10 months of cough and exertional dyspnea. One year after resection of the mass, a metastatic lesion was removed from the contralateral lung. The literature on this unusual pulmonary lesion is reviewed.

    View details for Web of Science ID 000072936200005

    View details for PubMedID 9559231

  • Bronchiolitis obliterans after lung transplantation - Detection using expiratory HRCT CHEST Leung, A. N., Fisher, K., Valentine, V., Girgis, R. E., Berry, G. J., Robbins, R. C., Theodore, J. 1998; 113 (2): 365-370


    The objective of this study was to determine if air trapping, as detected on expiratory high-resolution CT (HRCT), is useful as an indicator of bronchiolitis obliterans (BO) in lung transplant recipients. MATERIALS andCorresponding inspiratory and expiratory HRCT images at five different levels and spirometry were obtained in 21 lung transplant recipients. Eleven patients had BO proved by transbronchial biopsy specimens; the remaining 10 patients had no pathologic or functional evidence of airways disease. Two "blinded" observers assessed the inspiratory images for the presence of bronchiectasis and mosaic pattern of lung attenuation, and the expiratory images for presence and extent of air trapping. Statistical comparison of the frequency of HRCT findings between patients with and without BO was performed using Fisher's Exact Test.On inspiratory images, bronchiectasis and mosaic pattern of lung attenuation were present in 4 (36%) and 7 (64%) of 11 patients with BO, and 2 (20%) and 1 (10%) of 10 patients without BO (p>0.05 and p<0.05), respectively. The sensitivity, specificity, and accuracy of bronchiectasis and mosaic pattern for BO were 36%, 80%, and 57%, and 64%, 90%, and 70%, respectively. On expiratory images, air trapping was found in 10 of 11 (91%) patients with BO compared to 2 of 10 (20%) patients without BO (p<0.002). Air trapping was found to have a sensitivity of 91%, specificity of 80%, and accuracy of 86% for BO. Air trapping was identified in one patient with BO who had normal results of baseline spirometric function tests.Air trapping, as detected on expiratory HRCT, was the most sensitive and accurate radiologic indicator of BO in the lung transplant population.

    View details for Web of Science ID 000072002900022

    View details for PubMedID 9498953

  • Clinics in diagnostic imaging (27). Sarcoidosis. Singapore medical journal Leung, A. N. 1997; 38 (7): 302-304


    A 44-year-old Caucasian man presented with third-degree heart block. Chest radiograph and high-resolution computed tomography (HRCT) of the thorax showed mediastinal and bilateral hilar lymphadenopathy associated with a diffuse, bilateral micronodular pattern. The HRCT findings and differential diagnosis of sarcoidosis are reviewed.

    View details for PubMedID 9339099

  • Spiral CT of the thorax in daily practice: Optimization of technique JOURNAL OF THORACIC IMAGING Leung, A. N. 1997; 12 (1): 2-10


    Effective utilization of spiral computed tomography (CT) technology in imaging of the thorax requires an understanding of technical parameters that affect image and scan quality. This article discusses how operator-controlled scan parameters can be optimized to achieve diagnostic and cost-effective examinations appropriate for daily clinical practice.

    View details for Web of Science ID A1997WA70200002

    View details for PubMedID 8989754

  • MRI of pulmonary embolism using Gd-DTPA-polyethylene glycol polymer enhanced 3D fast gradient echo technique in a canine model MAGNETIC RESONANCE IMAGING Li, K. C., Pelc, L. R., NAPEL, S. A., Goris, M. L., Lin, D. T., SONG, C. K., Leung, A. N., Rubin, G. D., HOLLETT, M. D., Harris, D. P. 1997; 15 (5): 543-550


    This study was to evaluate the accuracy of MR angiography (MRA) using a Gd-DTPA-polyethylene glycol polymer (Gd-DTPA-PEG) with a 3D fast gradient echo (3D fgre) technique in diagnosing pulmonary embolism in a canine model. Pulmonary emboli were created in six mongrel dogs (20-30 kg) by injecting tantalum oxide-doped autologous blood clots into the femoral veins via cutdowns. MRI was performed with a 1.5 T GE Signa imager using a 3D fgre sequence (11.9/2.3/15 degrees) following intravenous injection of 0.06 mmol Gd/kg of Gd-DTPA-PEG. The dogs were euthanized and spiral CT of the lungs were then obtained on the deceased dogs. The MRI images were reviewed independently and receiver-operating-characteristic (ROC) curves were used for statistical analysis using spiral CT results as the gold standard. The pulmonary emboli were well visualized on spiral CT. Out of 108 pulmonary segments in the six dogs, 24 contained emboli >2 mm and 27 contained emboli < or = 2 mm. With unblinded review, MRI detected 79% of emboli >2 mm and only 48% of emboli < or = 2 mm. The blinded review results were significantly worse. Gd-DTPA-PEG enhanced 3D fgre MRI is potentially able to demonstrate pulmonary embolism with fairly high degree of accuracy, but specialized training for the interpretations will be required.

    View details for Web of Science ID A1997XM76800004

    View details for PubMedID 9253998

  • Radiologic manifestations of lymphoma in the thorax AMERICAN JOURNAL OF ROENTGENOLOGY Au, V., Leung, A. N. 1997; 168 (1): 93-98

    View details for Web of Science ID A1997VZ55500019

    View details for PubMedID 8976927

  • Optimization of thoracic spiral CT: Effects of iodinated contrast medium concentration RADIOLOGY Rubin, G. D., Lane, M. J., Bloch, D. A., Leung, A. N., Stark, P. 1996; 201 (3): 785-791


    To determine the effect of varying iodine concentration on arterial enhancement and perivenous artifact during thoracic spiral computed tomographic (CT) scanning.One hundred thirty-eight outpatients received 15.0 g (n = 76) or 22.5 g (n = 62) of iodine (300 mg/mL iodine) while undergoing thoracic spiral CT. Patients received either undiluted contrast medium, 1:1 normal saline dilution, or 3:1 normal saline dilution. Contrast medium was injected at a flow rate determined to deliver the entire iodine dose within 40 seconds. Attenuation was measured within arteries and veins. Three blinded thoracic radiologists independently graded perivenous artifact and arterial enhancement.Perivenous artifacts were statistically significantly reduced with successive iodine dilution (P < .002). Arterial enhancement was statistically significantly better with 15.0 g of iodine diluted 1:1 when compared with the same iodine dose undiluted or diluted 3:1 (P < .01). Arterial enhancement achieved with 15.0 g of iodine diluted 1:1 was not statistically significantly lower than that achieved with 22.5 g of iodine diluted 1:1 (P > .31); however, venous artifact was greater with 22.5 g of iodine (P < .004).Reduced iodine concentration appears to diminish perivenous artifact and to result in improved arterial enhancement during thoracic spiral CT.

    View details for Web of Science ID A1996VU50000033

    View details for PubMedID 8939232

  • Radiographic appearance of central venous catheters AMERICAN JOURNAL OF ROENTGENOLOGY Fisher, K. L., Leung, A. N. 1996; 166 (2): 329-337


    Central venous catheters (CVCs) are defined as venous access devices whose tips terminate in the superior or inferior vena cava, regardless of insertion site. CVCs allo reliable, painless, and repeated entry into the venous system and are commonly used for the administration of IV therapy, parenteral nutrition, and blood products as well as for the periodic blood sampling, hemodynamic monitoring, and hemodialysis. Catheter composition and design vary and depend on the duration of intended use and specific functions required. The purpose of this essay is to illustrate commonly used catheters, discuss factors governing catheter selection, and review important catheter-related complications.

    View details for Web of Science ID A1996TR34300018

    View details for PubMedID 8553941

Conference Proceedings

  • Computed tomographic angiography: Historical perspective and new state-of-the-art using multi detector-row helical computed tomography Rubin, G. D., Shiau, M. C., Schmidt, A. J., Fleischmann, D., Logan, L., Leung, A. N., Jeffrey, R. B., Napel, S. LIPPINCOTT WILLIAMS & WILKINS. 1999: S83-S90


    Since its clinical introduction in 1991, volumetric computed tomography scanning using spiral or helical scanners has resulted in a revolution for diagnostic imaging. In addition to new applications for computed tomography, such as computed tomographic angiography and the assessment of patients with renal colic, many routine applications such as the detection of lung and liver lesions have substantially improved. Helical computed tomographic technology has improved over the past eight years with faster gantry rotation, more powerful X-ray tubes, and improved interpolation algorithms, but the greatest advance has been the recent introduction of multi detector-row computed tomography scanners. These scanners provide similar scan quality at a speed gain of 3-6 times greater than single detector-row computed tomography scanners. This has a profound impact on the performance of computed tomography angiography, resulting in greater anatomic coverage, lower iodinated contrast doses, and higher spatial resolution scans than single detector-row systems.

    View details for Web of Science ID 000084391500012

    View details for PubMedID 10608402


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