ACS Clinical Scholar in Residence Mentors

Mark E. Cohen, PhD

Statistical Manager, Continuous Quality Improvement, Division of Research and Optimal Patient Care, American College of Surgeons, Chicago, IL

Dr. Cohen received a PhD in psychology from the University of Illinois, Chicago, and also completed graduate-level coursework in applied statistics at DePaul University, Chicago. Dr. Cohen was a National Institutes of Health postdoctoral fellow at the University of Wisconsin, Madison, and taught at Lake Forest College, Lake Forest, IL. Before coming to the College in 2008, he worked at a U.S. Navy Medical Research Laboratory for 28 years as a statistician and as technical (research) director. Dr. Cohen has authored 165 peer-reviewed articles. He manages the CQI statistics team which is responsible for profiling analytics for the ACS National Surgical Quality Improvement Program (ACS NSQIP), Pediatric NSQIP, and the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP), as well as other quantitative efforts involving ACS staff, consultants, and clinical scholars.

Bruce L. Hall, MD, PhD, MBA, FACS

Bruce Lee Hall, MD, PhD, MBA, is the interim vice chancellor of Human Health Sciences and the chief clinical officer for UC Davis Health.

Hall’s areas of expertise include performance measurement, quality improvement, and facilitating change. For more than a decade, he has taught health care economics and management courses, and guest lectured on topics including health care economics, insurance theory, health policy, health care management, and industry change. Hall has been recognized three times by Becker's Hospital Review's list of "patient safety experts to know" in 2020, 2022, and 2023.

In addition, he has served as an ACS liaison to the National Quality Forum, the Centers for Medicare and Medicaid Services, the Centers for Disease Control and Prevention, and the Joint Commission. He has been a member of the leadership team for the ACS’ National Surgical Quality Improvement Program since its founding more than 20 years ago.

Hall earned his BA degree in biochemical sciences from Princeton University in 1984; his PhD in immunology from Duke University in 1991 as a member of the National Institutes of Health Medical Scientist Training Program; his MD degree from Duke University in 1992; and his MBA from Harvard University in 2000. 

Clifford Ko, MD, MS, MSHS, FACS

Director, Division of Research and Optimal Patient Care, American College of Surgeons (ACS), Chicago, IL

Dr. Ko is the Director of the Division of Research and Optimal Patient Care at the American College of Surgeons (ACS) where he oversees all the quality improvement and accreditation/verification programs and activities of the division, including those related to bariatric, cancer, pediatric, and trauma surgeries. He also oversees the Surgeon Specific Registry (SSR), the Coalition for Quality in Geriatric Surgery (CQGS), and the Improving Surgical Care and Recovery (ISCR) project informed for enhanced recovery protocols. Dr. Ko also serves as the Director of the ACS National Surgical Quality Improvement Program (ACS NSQIP), and professor of surgery at the University of California, Los Angeles. He is a double board-certified surgeon, specializing in general and colorectal surgery, and a formally trained health services researcher. Prior to working at the ACS, he served as a research scientist at the RAND Corporation. Dr. Ko has published nearly 400 peer-reviewed articles, written more than 20 book chapters, and received peer-reviewed funding from several sources including the National Institutes of Health and the Agency for Healthcare Research and Quality. He has extensive experience in guiding residents and fellows conducting research on health outcomes.

Avery Nathens, MD, MPH, PhD

Dr. Nathens is the Medical Director of Trauma Quality Programs at the American College of Surgeons, Professor of Surgery at the University of Toronto and a practicing trauma surgeon and the medical director of trauma at Canada’s largest trauma center. He completed his trauma and critical care fellowship at Harborview Medical Center at the University of Washington and joined the faculty there in 2000 as Director of Surgical Critical Care and the Director, Acute Care Section of the CDC - funded Harborview Injury Prevention and Research Center. As Medical Director of Trauma Quality Programs at the ACS, he oversees the Trauma Center Verification and Review Program and the  Trauma Quality Improvement Program (TQIP), where centers receive benchmarking reports allowing them to compare their performance to their peers. 

Dr. Nathens holds a PhD from the University of Toronto, a Masters in Public Health from the University of Washington, and has cross appointments at the Institute of Clinical Evaluative Sciences (IC/ES) and the Institute of Health Policy, Management, and Evaluation at the University of Toronto. He holds the DeSouza Chair in Trauma Research and has published over 450 manuscripts including many landmark peer-reviewed papers in the Lancet, NEJM, and JAMA. He has been awarded several million dollars in funding from the NIH, CDC, and other agencies for his research evaluating trauma care.

Ronald J. Weigel, MD, PhD

Ronald J. Weigel, MD, PhD, received his BS and MS in Chemical Engineering from the Massachusetts Institute of Technology, his MD and PhD in Molecular Biophysics and Biochemistry from Yale University, and MBA from the Wharton School of Business at the University of Pennsylvania. He trained in general surgery at Duke University Medical Center. Dr. Weigel became a tenured professor at Stanford University where he developed a highly successful practice in breast and endocrine surgery and built an NIH-funded laboratory studying mechanisms of gene regulation in cancer. In 2005, Dr. Weigel was recruited to the University of Iowa as the Professor and Chair of the Department of Surgery. He was elected to the National Academy of Medicine, has served as a director of the American Board of Surgery, past Chair of the Board of Governors for the American College of Surgeons, and past president of the Society of Surgical Oncology and the Central Surgical Association. He is currently the president of the American Surgical Association. In 2023, Dr. Weigel became the Medical Director for Cancer Programs at the American College of Surgeons. When not at work, he enjoys spending time with his wife, Paula, and their four children.