Dr. Mullen attended the University of Virginia, graduating in 1987 with a BA in Chemistry and Spanish. She then attended medical school at Columbia University College of Physicians and Surgeons, graduating in 1991. After an internship in Internal Medicine at the Hospital of the University of Pennsylvania, she returned to Columbia Presbyterian Medical Center (now New York Presbyterian Hospital) for her residency in Diagnostic Radiology. She served at Co-Chief Resident from 1995 to 1996. Dr. Mullen completed her fellowship in Cross-Sectional Imaging (Ultrasound, CT and MRI) at Johns Hopkins Hospital in 1997.

Dr. Mullen then worked in private practice for 5 years, gaining experience in general radiology, and developing interest and expertise in breast imaging, womens imaging, and body imaging. She joined Johns Hopkins Radiology in 2002, and has been based at Johns Hopkins Imaging at Green Spring Station. Dr. Mullen has expertise in screening and diagnostic mammography, breast ultrasound, breast MRI, and breast interventional procedures, as well as general ultrasound and bone densitometry. Dr. Mullen is currently the Director of Ultrasound at Green Spring.