- Radioimmunotherapy: Patients receive indium In 111 ibritumomab tiuxetan IV over 10 minutes on day 1 (for imaging only); yttrium Y 90 ibritumomab tiuxetan IV over 10 minutes on day 8; and rituximab IV over 3-4 hours on days 1, 8, 15, 22, 29, and 36.