[1] Univ Montreal, Dept Phys, Complexe Sci,1375 Ave Therese Lavoie Roux, Montreal, PQ H2V 0B3, Canada
[2] Ctr Rech CHUM, 900 Rue St Denis, Montreal, PQ H2X 3H8, Canada
[3] Ctr Hosp Univ Montreal CHUM, Dept Radiooncol, 1051 Rue Sanguinet, Montreal, PQ H2X 3E4, Canada
[4] Natl Phys Lab, Chem Med & Environm Sci Dept, Hampton Rd, Teddington TW11 0LW, Middx, England