title: Preface.
authors.affiliation: Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA. Electronic address: Drew.Torigian@uphs.upenn.edu.
authors.forename: Drew A
authors.initials: DA
authors.lastname: Torigian
authors.affiliation: Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA. Electronic address: Abass.Alavi@uphs.upenn.edu.
authors.forename: Abass
authors.initials: A
authors.lastname: Alavi