SPECT VERSUS CT AND/OR MR-IMAGING IN DISTINGUISHING TUMOR RECURRENCE FROM RADIATION NECROSIS IN THE BRAIN - PRELIMINARY FINDINGS

Single photon emission computed tomography (SPECT) using the recently introduced substance 99m-Tc-hexakis-MIBI was compared with CT and/or MR imaging in differentiating radiation necrosis from recurrent brain tumour 99m-Tc-hexakis-MIBI has proved a specific marker for vital tumour cells, similar to 201 Tl, but offers more intense accumulation 35 SPECT scans were assessed in 28 patients with primary malignant brain tumours who had already undergone surgery, radiotherapy and chemotherapy. Lacking confirmation at surgery or autopsy, final diagnosis was established on the basis of subsequent armour evolution at CT and/or MR. There were 7 false negatives with SPECT which were due to small tumour size and/or the vicinity of the choroid plexuses which show increased radionuclide uptake with this technique; there was only one certain false positive. These preliminary findings demonstrate that SPECT with 99m-Tc-hexakis-MIBI is a useful adjunct to CT and/or MR imaging in distinguishing radiation necrosis from tumour recurrence in the brain when the lesions involve large highly malignant tumours at some distance from the choroid plexuses and which do not have mainly cystic necrotic central areas. There is a need for a radioactive substance combining the advantages of 99m-Tc-hexakis-MIBI with greater lesion sensitivity and which does not enhance normal anatomical structures.