Patients receive 90 Y-HAT in escalating doses to determine the highest dose that can be safely given. The first group of three patients receives a low dose and, if there are no significant side effects at that dose, the next three patients receive a higher dose. This continues with subsequent groups until the maximum study dose is reached. 90 Y-HAT is given through a vein (intravenous (IV)) over a 2-hour period. In addition, a drug called Pentetate Calcium Trisodium Inj (Ca-DTPA) is given via IV over 5 hours for 3 days to help reduce the side effects of the 90Y-HAT. In some patients, the 90 Y-HAT may also be attached to a radioactive metal called Indium-111 to monitor what happens to the injected material. During infusion of the drug, patients undergo PET scanning to trace the path of the injected material in the body. For this procedure, the patient lies in the scanner, remaining in one position during the entire infusion.