- Nuclear Medicine CSF flow studies are required within the 2 weeks prior to study entry for all solid tumor patients. In leukemia/lymphoma patients a CSF flow study is only required if CSF analysis or an MRI suggests that there is a blockage to CSF flow. Patients with clinical evidence of obstructive hydrocephalus are not eligible for this protocol. Nor are patients with compartmentalization of CSF flow as documented by radioisotope Indium111 or Technetium99-DTPA flow eligible for this protocol. If a CSF flow block or compartmentalization is demonstrated, focal radiotherapy to the site of the block to restore flow followed by a repeat CSF flow study demonstrating clearing of the blockage is required for the patient to be eligible for the study.