Clinical Focus

  • Body Imaging

Academic Appointments

  • Clinical Associate Professor, Radiology

Professional Education

  • Medical Education: University of Southern California Keck School of Medicine (2006) CA
  • Residency: Santa Clara Valley Medical Center (2011) CA
  • Fellowship: Stanford University Radiology Fellowships (2014) CA
  • Internship: Santa Clara Valley Medical Center Internal Medicine Residency (2007) CA
  • Board Certification: American Board of Radiology, Diagnostic Radiology (2011)

All Publications

  • Interobserver agreement between eight observers using IOTA simple rules and O-RADS lexicon descriptors for adnexal masses. Abdominal radiology (New York) Antil, N., Raghu, P. R., Shen, L., Tiyarattanachai, T., Chang, E. M., Ferguson, C. W., Ho, A. A., Lutz, A. M., Mariano, A. J., Morimoto, L. N., Kamaya, A. 2022


    PURPOSE: To evaluate interobserver agreement in assigning imaging features and classifying adnexal masses using the IOTA simple rules versus O-RADS lexicon and identify causes of discrepancy.METHODS: Pelvic ultrasound (US) examinations in 114 women with 118 adnexal masses were evaluated by eight radiologists blinded to the final diagnosis (4 attendings and 4 fellows) using IOTA simple rules and O-RADS lexicon. Each feature category was analyzed for interobserver agreement using intraclass correlation coefficient (ICC) for ordinal variables and free marginal kappa for nominal variables. The two-tailed significance level (a) was set at 0.05.RESULTS: For IOTA simple rules, interobserver agreement was almost perfect for three malignant lesion categories (M2-4) and substantial for the remaining two (M1, M5) with k-values of 0.80-0.82 and 0.68-0.69, respectively. Interobserver agreement was almost perfect for two benign feature categories (B2, B3), substantial for two (B4, B5) and moderate for one (B1) with k-values of 0.81-0.90, 0.69-0.70 and 0.60, respectively. For O-RADS, interobserver agreement was almost perfect for two out of ten feature categories (ascites and peritoneal nodules) with k-values of 0.89 and 0.97. Interobserver agreement ranged from fair to substantial for the remaining eight feature categories with k-values of 0.39-0.61. Fellows and attendings had ICC values of 0.725 and 0.517, respectively.CONCLUSION: O-RADS had variable interobserver agreement with overall good agreement. IOTA simple rules had more uniform interobserver agreement with overall excellent agreement. Greater reader experience did not improve interobserver agreement with O-RADS.

    View details for DOI 10.1007/s00261-022-03580-8

    View details for PubMedID 35763052

  • The American Broncho-Esophagological Association Position Statement on Swallowing Fluoroscopy. The Laryngoscope Dhar, S. I., Nativ-Zeltzer, N., Starmer, H., Morimoto, L. N., Evangelista, L., O'Rourke, A., Fritz, M., Rameau, A., Randall, D., Cates, D., Allen, J., Postma, G., Kuhn, M., Belafsky, P. 2022


    OBJECTIVES: To develop an expert consensus statement on the clinical use of swallowing fluoroscopy in adults that reduces practice variation and identifies opportunities for quality improvement in the care of patients suffering from swallowing impairment.METHODOLOGY: A search strategist reviewed data sources (PubMed, Embase, Cochrane, Web of Science, Scopus) to use as evidence for an expert development group to compose statements focusing on areas of controversy regarding swallowing fluoroscopy. Candidate statements underwent two iterations of a modified Delphi protocol to reach consensus.RESULTS: A total of 2184 publications were identified for title and abstract review with 211 publications meeting the criteria for full text review. Of these, 148 articles were included for review. An additional 116 publications were also included after reviewing the references of the full text publications from the initial search. These 264 references guided the authors to develop 41 candidate statements in various categories. Forty statements encompassing patient selection, fluoroscopic study choice, radiation safety, clinical team dynamics, training requirements, videofluoroscopic swallow study and esophagram techniques, and interpretation of swallowing fluoroscopy met criteria for consensus. One statement on esophagram technique reached near-consensus.CONCLUSIONS: These 40 statements pertaining to the comprehensive use of swallowing fluoroscopy in adults can guide the development of best practices, improve quality and safety of care, and influence policy in both the outpatient and inpatient settings. The lack of consensus on some aspects of esophagram technique likely reflects gaps in knowledge and clinical practice variation and should be a target for future research. Laryngoscope, 2022.

    View details for DOI 10.1002/lary.30177

    View details for PubMedID 35543231

  • Automated Identification and Measurement Extraction of Pancreatic Cystic Lesions from Free-Text Radiology Reports Using Natural Language Processing. Radiology. Artificial intelligence Yamashita, R., Bird, K., Cheung, P. Y., Decker, J. H., Flory, M. N., Goff, D., Morimoto, L. N., Shon, A., Wentland, A. L., Rubin, D. L., Desser, T. S. 2022; 4 (2): e210092


    Purpose: To automatically identify a cohort of patients with pancreatic cystic lesions (PCLs) and extract PCL measurements from historical CT and MRI reports using natural language processing (NLP) and a question answering system.Materials and Methods: Institutional review board approval was obtained for this retrospective Health Insurance Portability and Accountability Act-compliant study, and the requirement to obtain informed consent was waived. A cohort of free-text CT and MRI reports generated between January 1991 and July 2019 that covered the pancreatic region were identified. A PCL identification model was developed by modifying a rule-based information extraction model; measurement extraction was performed using a state-of-the-art question answering system. The system's performance was evaluated against radiologists' annotations.Results: For this study, 430426 free-text radiology reports from 199783 unique patients were identified. The NLP model for identifying PCL was applied to 1000 test samples. The interobserver agreement between the model and two radiologists was almost perfect (Fleiss kappa = 0.951), and the false-positive rate and true-positive rate were 3.0% and 98.2%, respectively, against consensus of radiologists' annotations as ground truths. The overall accuracy and Lin concordance correlation coefficient for measurement extraction were 0.958 and 0.874, respectively, against radiologists' annotations as ground truths.Conclusion: An NLP-based system was developed that identifies patients with PCLs and extracts measurements from a large single-institution archive of free-text radiology reports. This approach may prove valuable to study the natural history and potential risks of PCLs and can be applied to many other use cases.Keywords: Informatics, Abdomen/GI, Pancreas, Cysts, Computer Applications-General (Informatics), Named Entity Recognition Supplemental material is available for this article. © RSNA, 2022See also commentary by Horii in this issue.

    View details for DOI 10.1148/ryai.210092

    View details for PubMedID 35391762

  • Ultrasound Liver Imaging Reporting and Data System (US LI-RADS) Visualization Score: a reliability analysis on inter-reader agreement. Abdominal radiology (New York) Tiyarattanachai, T., Bird, K. N., Lo, E. C., Mariano, A. T., Ho, A. A., Ferguson, C. W., Chima, R. S., Desser, T. S., Morimoto, L. N., Kamaya, A. 2021


    BACKGROUND & AIM: The American College of Radiology Ultrasound Liver Imaging Reporting and Data System (ACR US LI-RADS) Visualization Score conveys the expected level of sensitivity of screening and surveillance ultrasound exams in patients at risk for hepatocellular carcinoma (HCC). We sought to determine inter-reader agreement of the Visualization Score which is currently unknown.METHODS: Consecutive 6998 ultrasound HCC screening and surveillance studies in 3115 patients from 2017 to 2020 were retrospectively retrieved. Of these, 6154 (87.9%) studies were Visualization A (No or minimal limitations), 709 (10.1%) were Visualization B (Moderate limitations), and 135 (1.9%) were Visualization C (Severe limitations). Randomly sampled 90 studies, with 30 studies in each Visualization category, were included for analysis. Nine radiologists (3 senior attendings, 3 junior attendings and 3 body imaging fellows) blinded to the original categorization independently reviewed each study and assigned a Visualization Score. Intraclass correlation coefficient (ICC) was used to quantify inter-reader agreement.RESULTS: ICC among all 9 radiologists was 0.70 (95% CI 0.63-0.77). ICCs among senior attendings, junior attendings and body imaging fellows were 0.68 (CI 0.58-0.76), 0.72 (CI 0.62-0.80) and 0.76 (CI 0.68-0.83), respectively. Subgroup analysis by liver parenchyma was further performed. ICC was highest in the patient group with normal liver parenchyma (0.69, CI 0.56-0.81), followed by steatosis (0.66, CI 0.54-0.79) and cirrhosis (0.58, CI 0.43-0.73), respectively.CONCLUSIONS: US LI-RADS Visualization Score is a reliable tool with good inter-reader agreement that can be used to indicate the expected level of sensitivity of a screening and surveillance ultrasound examination for detecting focal liver observations.

    View details for DOI 10.1007/s00261-021-03067-y

    View details for PubMedID 34228197

  • Reduced dose CT with model-based iterative reconstruction compared to standard dose CT of the chest, abdomen, and pelvis in oncology patients: intra-individual comparison study on image quality and lesion conspicuity. Abdominal radiology Morimoto, L. N., Kamaya, A., Boulay-Coletta, I., Fleischmann, D., Molvin, L., Tian, L., Fisher, G., Wang, J., Willmann, J. K. 2017


    To compare image quality and lesion conspicuity of reduced dose (RD) CT with model-based iterative reconstruction (MBIR) compared to standard dose (SD) CT in patients undergoing oncological follow-up imaging.Forty-four cancer patients who had a staging SD CT within 12 months were prospectively included to undergo a weight-based RD CT with MBIR. Radiation dose was recorded and tissue attenuation and image noise of four tissue types were measured. Reproducibility of target lesion size measurements of up to 5 target lesions per patient were analyzed. Subjective image quality was evaluated for three readers independently utilizing 4- or 5-point Likert scales.Median radiation dose reduction was 46% using RD CT (P < 0.01). Median image noise across all measured tissue types was lower (P < 0.01) in RD CT. Subjective image quality for RD CT was higher (P < 0.01) in regard to image noise and overall image quality; however, there was no statistically significant difference regarding image sharpness (P = 0.59). There were subjectively more artifacts on RD CT (P < 0.01). Lesion conspicuity was subjectively better in RD CT (P < 0.01). Repeated target lesion size measurements were highly reproducible both on SD CT (ICC = 0.987) and RD CT (ICC = 0.97).RD CT imaging with MBIR provides diagnostic imaging quality and comparable lesion conspicuity on follow-up exams while allowing dose reduction by a median of 46% compared to SD CT imaging.

    View details for DOI 10.1007/s00261-017-1140-5

    View details for PubMedID 28417170

  • The Use of Patient and Family Advisory Councils to Improve Patient Experience in Radiology. AJR. American journal of roentgenology Kuhn, K. J., Mickelsen, L. J., Morimoto, L. N., Larson, D. B. 2016; 207 (5): 965-970


    Rising costs and widespread inefficiencies in current practices have prompted a paradigm shift in American health care from volume- to value-based care with patients and families assuming a central role. Patient and family advisory councils (PFACs) are particularly compelling as a strategy for using patient and family engagement for process improvement. Although relatively new in the radiologic community, PFACs can be a powerful tool in improving patient experience.PFACs are a particularly powerful method of patient and family engagement that can be used in effecting meaningful change in practice. This valuable resource resides within most hospitals and is generally readily accessible. In the era of value-based care, it is essential that radiologists actively engage with patients to improve efficiency, reduce expenditures, and maximize patient satisfaction.

    View details for PubMedID 27440525