The goal of this study is to develop imaging based methods to accurately determine the energy absorbed (absorbed dose) by tumor tissue and bone marrow after radioimmunotherapy with I-131 tositumomab . The administration of the radioactive, iodine-131 labeled, monoclonal antibody I-131 tositumomab, (also known as Bexxar) is part of the patient's clinical treatment protocol. For the absorbed dose measurement, investigators at the University of Michigan are evaluating a new Nuclear Medicine SPECT/CT imaging system . This new camera combines a CT imaging system in addition to a Nuclear Medicine SPECT scanner. CT scans allow the doctors to see a high quality picture of your internal organs. The Nuclear Medicine SPECT scanner allows the doctors to see the uptake of the radioactive I-131 including the tumor sites. The improved imaging using the SPECT/CT enables more accurate calculation of the energy absorbed by tumor tissue and bone marrow. Using the results from these calculations and clinical follow up data, the researchers will investigate the relationship between the absorbed dose to the tumor and the patient's tumor response as well as the relationship between the absorbed dose to the bone marrow and the bone marrow toxicity. These relationships can potentially be used in the future by doctors to help determine how much radioactive I-131 to administer to each patient to get optimal results.

Inclusion Criteria:

• • Clinically stable patients undergoing I-131 Tositumomab (Bexxar) for treatment of Non-Hodgkin Lymphomas

Exclusion Criteria:

• • Clinical instability

  • Patients who are unable to lie flat on the imaging systems long enough to permit imaging protocols to be performed
  • Refusal to provide informed consent
  • Patients who are pregnant

Clinically stable patients undergoing I-131 Tositumomab (Bexxar) for treatment of Non-Hodgkin Lymphomas