NTV obtained by MRI before and after treatment. Tumour volumes were normalized by the means of the pretreatment values of each group ( n =9 per group, except n =13 for nanobots in urea and n =7 for high-dose 131 I-nanobots in water and urea, biological replicates). Data are presented as mean values and error bars represent the s.e.m. Statistical significances are based on a two-tailed unpaired t -test. Inset: tumour volume changes with respect to pretreatment (see e for legend).
