Johns Hopkins All Children's Hospital

Meet Our Radiology Team

Michael Collard, MD

Michael Collard, MD

Radiology
Dr. Collard specializes in pediatric interventional radiology at Johns Hopkins All Children’s Hospital. He joined the medical staff in 2021. Dr. Collard earned his medical degree from the University of Missouri Kansas City School of Medicine in Kansas City, Missouri. He completed an internship in internal medicine at the University of Missouri Kansas City School of Medicine and a residency in diagnostic radiology at the University of Texas Southwestern Medical Center in Dallas. He then completed a fellowship in vascular and interventional radiology at Massachusetts General Hospital/Harvard Medical School in Boston, followed by a fellowship in pediatric radiology with an emphasis in interventional radiology at Boston Children’s Hospital/Harvard Medical School.
View Michael Collard’s Bio
Jane Cook, DO

Jane Cook, DO

Radiology
Dr. Cook specializes in pediatric radiology with a focus on PET/CT and musculoskeletal imaging at Johns Hopkins All Children’s Hospital. She joined the hospital staff in 2019.
View Jane Cook’s Bio
Kimberly Fagen, MD

Kimberly Fagen, MD

Radiology
Dr. Fagen specializes in pediatric radiology at Johns Hopkins All Children’s. She joined the hospital staff in 2019. Dr. Fagen earned her medical degree from the Uniformed Services University of the Health Sciences in Bethesda, Maryland. She completed her internship at National Capital Consortium and residency in diagnostic radiology at Naval Medical Center San Diego. She completed a fellowship in pediatric radiology at Children’s National Medical Center.
View Kimberly Fagen’s Bio
Christopher Keup, MD

Christopher Keup, MD

Radiology
Dr. Keup specializes in pediatric radiology at Johns Hopkins All Children’s Hospital. He joined the hospital staff in 2019. Dr. Keup also serves in the U.S. Army Reserve.  He is currently attached to the Army Medical Department Personnel Management Command in Forest Park, Georgia, and is a Lieutenant Colonel in the Medical Corps. Dr. Keup earned his medical degree from the University of Missouri in Columbia, Missouri. He completed an internship in internal medicine from the University of Missouri-Kansas City in Kansas City, Missouri, followed by a residency in diagnostic radiology from the University of Missouri-Kansas City and a fellowship in pediatric radiology from Children’s Mercy Hospital in Kansas City, Missouri.
View Christopher Keup’s Bio
Javier Quintana, MD

Javier Quintana, MD

Radiology
Dr. Quintana is a radiologist at Johns Hopkins All Children’s Hospital. He joined hospital staff in 2010. Dr. Quintana earned his medical degree at the University of South Florida. He trained in general pediatrics at Jackson Memorial Hospital/University of Miami and completed a diagnostic radiology residency at Geisinger Medical Center in Danville, Pennsylvania. Dr. Quintana completed a pediatric radiology fellowship at Children’s Hospital of Philadelphia. He is fluent in Spanish.
View Javier Quintana’s Bio
William Schaaf, MD

William Schaaf, MD

Radiology
Dr. Schaaf is a graduate of the Drexel University College of Medicine (formerly Medical College of Pennsylvania Hahnemann School of Medicine). He completed his residency in diagnostic radiology at Eastern Virginia Medical School, Norfolk, VA, where he served as chief resident. He also completed his pediatric radiology fellowship at Cincinnati Children’s Hospital Medical Center. Dr. Schaaf is board-certified in radiology and board-admissible in pediatric radiology.
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Erica Schallert, MD

Erica Schallert, MD

Radiology
Dr. Schallert specializes in pediatric radiology at Johns Hopkins All Children’s Hospital. She joined the medical staff in 2022 and sees patients on our main campus in St. Petersburg, Florida. Dr. Schallert earned her medical degree from the University of Florida College of Medicine in Gainesville, Florida. She completed an internship at John Peter Smith Hospital in Fort Worth, Texas. She then completed a residency in diagnostic radiology from the University of Miami, Miller School of Medicine, Jackson Memorial Hospital in Miami, followed by a pediatric radiology fellowship at Baylor College of Medicine, Texas Children’s Hospital in Houston.
View Erica Schallert’s Bio

Christopher Francis, MD

Christopher Francis, MD

Radiology
Dr. Francis specializes in adult and pediatric interventional radiology. He is the section chief of Pediatric Interventional Radiology at Johns Hopkins All Children's, and is an assistant professor of Radiology in the University of South Florida (USF) Morsani College of Medicine. He joined the Johns Hopkins All Children’s medical staff in 2018.
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Sally Mitchell, MD

Sally Mitchell, MD

Radiology
Dr. Mitchell is an interventional radiologist at Johns Hopkins All Children’s. She joined the hospital staff in 2021. She was most recently director of pediatric interventional radiology and director of vascular anomalies interventional radiology at Johns Hopkins University School of Medicine in Baltimore.
View Sally Mitchell’s Bio

Susan Buffington MSN, APRN, CPNP

Susan Buffington MSN, APRN, CPNP


Paul Herlan MPAS, PA-C

Paul Herlan MPAS, PA-C


Natalie Mercado MPAS, PA-C

Natalie Mercado MPAS, PA-C


Michelle Walker MSN, APRN, CPNP

Michelle Walker MSN, APRN, CPNP