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Medical Team

Our board-certified radiologist physicians and technologists have the most advanced tools to provide diagnostic studies ranging from general X-ray and ultrasound to sophisticated nuclear medicine and magnetic resonance imaging (MRI).

Avanti Ambekar, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Avanti Ambekar, M.D., received her medical degree from Northwestern University Medical School before completing her residency at the University of California at San Francisco (UCSF). She completed fellowships in both neuroradiology and musculoskeletal imaging at UCSF, where she also served as chief resident in the department of radiology. She received a Certificate of Added Qualification in neuroradiology in 2008.

Dr. Ambekar currently practices at Mills-Peninsula and serves as clinical faculty in the department of radiology at UCSF. She is a member of the American Society of Head and Neck Radiology, the Radiological Society of North America and the American Society of Neuroradiology. Dr. Ambekar has published in Osteoporosis International and the International Journal of Gynecology and Obstetrics.

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Diane B. Baker, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Diana Baker, M.D., graduated from Stanford University School of Medicine in 1997, following undergraduate work at Stanford. She also completed her internship there. Dr. Baker completed a diagnostic radiology residency and fellowship in ultrasound at the University of California at San Francisco. She has practiced at Mills-Peninsula since 2003.

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Harriet Beth Borofsky, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Harriet Borofsky, M.D., is the medical director of breast imaging at the Mills-Peninsula Women’s Center in San Mateo. Dr. Borofsky is regionally acknowledged as an expert in breast imaging.

She received her medical degree from Harvard University Medical School in 1988, following undergraduate work at Brown University. She completed fellowships in body imaging and mammography and a residency in radiology at Stanford University Hospital.

Dr. Borofsky has lectured and published on a variety of topics including new technology in early detection and diagnosis of breast cancer. She led implementation of the region’s first digital mammography and breast MRI program. She previously served on the clinical faculty at Stanford University. Dr. Borofsky is regionally acknowledged as an expert in breast imaging.

She has practiced at Mills-Peninsula since 1994 and serves as the medical director of breast imaging at the Mills-Peninsula Women’s Center in San Mateo.

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Kelly C. Broderick, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Kelly Broderick, M.D., received her medical degree from Harvard University Medical School in 1992, following undergraduate work at Pennsylvania State University. She is a board certified general radiologist specializing in breast imaging and ultrasound. Dr. Broderick completed a fellowship in ultrasound and a residency in radiology at the University of California at San Francisco. She has practiced at Mills-Peninsula since 1999.

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Thomas H. Farquhar, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Thomas Farquhar, M.D., received his medical degree from the University of California at Los Angeles (UCLA) School of Medicine in 2000. He completed undergraduate and graduate work at Stanford University and earned a Ph.D. in biomedical physics from the UCLA School of Medicine. Dr. Farquhar has authored multiple research publications and delivered several conference presentations in the field of positron emission tomography (PET), receiving awards from the Society of Nuclear Medicine and American Association of Physicists in Medicine. Following an internal medicine internship at the UCLA San Fernando Valley Internal Medicine Program, Dr. Farquhar completed his residency in diagnostic radiology at the University of California at San Francisco in 2005 and a fellowship in MRI at the University of California at San Diego in 2006.

He has practiced at Mills-Peninsula since 2006 and has a special interest in MRI and PET imaging. He is serving as the current department chairman.
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Lenora V. Fung, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Lenora Fung, M.D., completed her medical degree at the University of California at San Francisco (UCSF) in 1974, after completing undergraduate work at the University of California at Berkeley. She also completed an internship and a residency in diagnostic radiology at UCSF. Dr. Fung completed a fellowship in computed tomography (CT) and ultrasound at San Francisco General Hospital in 1981. She has practiced at Mills-Peninsula since 1999.

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Brian L. Johnson, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Brian Johnson, M.D., received his medical degree from Stanford University Medical School in 1976, following undergraduate work at Harvard University. He completed an internship in internal medicine at San Francisco General Hospital in 1977 and a residency in diagnostic radiology at the University of California at San Francisco in 1980. Dr. Johnson has practiced at Mills-Peninsula since 1980. He has served as medical director of the Department of Radiology at Mills-Peninsula since 1992 and medical director of the Mills-Peninsula School of Radiologic Technology since 1994.
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Arthur E. Li, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Arthur Li, M.D., completed his medical degree from the University of California at San Francisco in 1999, following undergraduate work at Harvard University. Dr. Li completed an internship in internal medicine and a residency in diagnostic radiology at Johns Hopkins Hospital in Baltimore. He also completed a fellowship in musculoskeletal imaging at the National Orthopedic Imaging Associates in San Francisco in 2005.

He is a co-author of the textbook "Magnetic Resonance Imaging in Sports Medicine & Orthopedics", and is a regular presenter at the “Annual Current Issues of Magnetic Resonance Imaging in Orthopedics and Sports Medicine” course in San Francisco.

Dr. Li has practiced at Mills-Peninsula since 2005 and has a special interest musculoskeletal, sports imaging and MRI.
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Gregory M. Lim, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology, Certification of Added Qualification, Interventional Radiology

Gregory Lim, M.D., received his medical degree from the University of California at San Francisco (UCSF) in 1989, following undergraduate and graduate work at Stanford University. He completed a Radiological Society of North America fellowship and a fellowship in interventional radiology at the University of California at San Diego. Dr. Lim completed a residency and internship in radiology at Virginia Mason Medical Center in Seattle. He also conducted a research fellowship at UCSF in June-August of 1986. Dr. Lim was selected to receive the national Radiologic Society of North America Fellowship award and was named the Cesare Gianturco Fellow for 1996.

Dr. Lim has practiced at Mills-Peninsula since 1997 and has a special interest in interventional radiology and interventional oncology.
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David S. Marcus, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

David Marcus, M.D., received his medical degree from the University of California at San Diego in 1987. After completing an internship at Mercy Hospital in San Diego in 1988, he completed his radiology residency training at the University of Arizona. He then served as a clinical instructor and fellow at the University of California at San Francisco, focusing on magnetic resonance imaging, ultrasound and computed tomography. In addition to cross-sectional body imaging, Dr. Marcus has special interest and experience in performing interventional radiologic procedures. He has practiced radiology in the San Mateo area since 1993.
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Kathleen M. McKenna, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Kathleen McKenna, M.D., received her medical degree from the University of California at Los Angeles School of Medicine in 1988, after completing undergraduate work at the University of California at Berkeley.

Dr. McKenna completed an internship in Internal Medicine at UCLA in 1988, residency in diagnostic radiology at the University of California, San Francisco in 1993, and a fellowship in Ultrasound at the University of California, San Francisco in 1994.

Dr. McKenna has been in practice at Mills-Peninsula since 1994 and has a special interest in Ultrasound and women’s imaging.
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Clay H. Napper, Jr., M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Clay Napper, M.D., completed his medical degree at Bowman Gray School of Medicine in Winston-Salem, N.C., in 1992. He received his radiology training at Stanford University, completing a fellowship in body imaging and residencies in diagnostic radiology and radiation oncology. Dr. Napper also completed an internship in internal medicine at the University of California at San Francisco in 1993.

Dr. Napper has a special interest in cancer imaging and also received training in radiation oncology at Stanford. He has practiced at Mills-Peninsula since 1999 and is the Director of PET imaging.
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Mark N. Pederson, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Mark Pederson, M.D., received his medical degree from the University of Iowa in 1972. He completed a radiology residency at University of California at San Francisco, a fellowship in abdominal imaging at New York University and an internship at Washington Hospital Center in Washington, D.C.

Dr. Pederson has practiced at Mills-Peninsula since 1982.

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Dorra Sellami, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

Dorra Sellami, M.D., received her medical degree from Tunis Medical School, Tunisia in 1998. Dr. Sellami received her radiology training in Tunisia, France and the U.S. She completed a residency in diagnostic radiology at the University of California at San Francisco (UCSF) in 2008, followed by a fellowship in women’s imaging. Dr. Sellami also completed an internship in general surgery at Mount Zion Medical Center in New York in 2004. She currently serves as visiting clinical faculty in breast imaging and ultrasound in the radiology department at UCSF. She has been in practice at Mills-Peninsula since 2009.
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William M. Stephenson, M.D.

Certified by the American Board of Radiology, Diagnostic Radiology

William Stephenson, M.D., received his medical degree from the University of California at San Diego School of Medicine in 1980, following undergraduate work at Stanford University. He completed a fellowship in computed tomography (CT) and ultrasound at the University of California at San Francisco (UCSF) and San Francisco General Hospital in 1985. Dr. Stephenson also completed a residency in diagnostic radiology and an internship in internal medicine at Dartmouth-Hitchcock Medical Center. Dr. Stephenson’s academic appointments include chief resident in radiology, instructor in clinical medicine at Dartmouth-Hitchcock Medical Center and clinical instructor in radiology at UCSF. He has practiced at Mills-Peninsula since 1985.
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John S. Wilson, Jr., M.D.

Certified by the American Board of Nuclear Medicine

John Wilson, M.D., received his medical degree from the University of California at San Francisco (UCSF). He also completed his residency training in skeletal radiology and orthopedic surgery and an internship in surgery at UCSF. Dr. Wilson's primary areas of interest are in mammography, CT and MRI. He has practiced at Mills-Peninsula since 1979.

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