Biodistribution of RICs in mice with CD20⁺ Raji xenografts. Uptake and retention of ²²⁷Th-p-benzyl-DOTA-rituximab (A-B), ²²⁷Th-p-benzyl-DOTA-trastuzumab (C-D) and 125I-ibritumomab-tiuexetan (E) in tumor xenografts and normal tissues were measured at various time points after injection into athymic mice bearing Raji xenografts. The activity per gram was measured using the 236-keV line of ²²⁷Th (A,C) and a germanium detector. (B,D) Activity per gram of ²²³Ra measured using the 154-keV line of ²²³Ra. The measured ²²⁷Th activities were normalized to an injection of 200 kBq/kg body weight. The activity of ¹²⁵I was measured using a γ counter and normalized to an injection of 7.5 MBq ⁹⁰Y/kg body weight. Error bars represent SE. A total of 6 to 8 mice were used.