[1] Univ Politecn Catalunya UPC, Inst Tecn Energet, Barcelona, Spain
[2] Univ Politecn Cataluna, Res Ctr Biomed Engn, Barcelona, Spain
[3] US FDA, Div Imaging Diagnost & Software Reliabil, OSEL, CDRH, Silver Spring, MD USA
[4] St James Hosp, Med Phys & Bioengn Dept, Dublin, Ireland