1 Frank Laboratory, Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD 20892; zsofia.kovacs@nih.gov jfrank@helix.nih.gov.
2 Frank Laboratory, Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD 20892.
3 National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892.