[1] Univ Penn, Perelman Sch Med, Philadelphia, PA 19104 USA
[2] Hosp Univ Penn, Dept Neurosurg, 3400 Spruce St, Philadelphia, PA 19104 USA
[3] Hosp Univ Penn, Dept Pathol & Lab Med, 3400 Spruce St, Philadelphia, PA 19104 USA
[4] Stony Brook Univ Hosp, Dept Pathol, Stony Brook, NY USA
[5] Hosp Univ Penn, Dept Radiol, 3400 Spruce St, Philadelphia, PA 19104 USA