[Thallium-201 single photon emission computed tomography in the evaluation of therapeutic response for brain tumors]

To evaluate the effectiveness of radiation and chemotherapy of malignant brain tumors, 201TlCl-SPECT (Tl-SPECT) was compared with CT and MRI. The subjects were 14 patients with malignant brain tumors; 12 malignant astrocytomas, 1 medulloblastoma and 1 malignant lymphoma. Tl-SPECT was performed before and immediately after the therapy. On the Tl-SPECT, count ratio (Tl-index) of tumor to normal brain tissue was measured. To evaluate the size of tumor, CT or MRI was performed before and immediately after the therapy, and 1-2 months after the therapy. The change of Tl-index immediately after therapy was compared with the change of the size of tumor. Though the change of Tl-index did not correlate with the change of tumoral size immediately after therapy, it correlated with the change of tumoral size 1-2 months after the therapy, i.e., it was thought that Tl-index reflected the change of tumoral size 1-2 months after the therapy. Tl-SPECT will be feasible for the evaluation of the effectiveness of the therapy for malignant brain tumors, because it reflects the effectiveness of the therapy earlier than CT or MRI.