1. Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218
2. Philips Research North America, Briarcliff Manor, New York 10510
3. Department of Computer Science, Johns Hopkins University, Baltimore, Maryland 21218
4. Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, Maryland 21231
5. Acoustic MedSystems Inc., Savoy, Illinois 61974
6. School of Computing, Queenˈs University, Kingston, Ontario K7L3N6, Canada
7. Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 and Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, Maryland 21231