Determination of peritumoral hypoperfusion volumes surrounding brain tumors using three-dimensional SPECT

We measured the volumes of peritumoral hypoperfusion surrounding brain metastases and meningiomas using three-dimensional 123I-IMP SPECT and compared the results with the volumes of peritumoral edema on MRI (T2). Eight patients with metastases and 18 with meningiomas underwent 123I-IMP SPECT and MRI before therapy. SPECT scans were performed to generate three-dimensional images using a panning visualization software (AVS-MV; application visualization system medical viewer). Based on the volume of each tumor on MRI (Gd), the ratio of peritumoral hypoperfusion volume associated with metastases on 3D-SPECT (H/T ratio: 25.5±23.2) was larger than the ratio for meningiomas (H/T ratio: 4.0±3.3, p<0.001). And the ratio of edematous volumes associated with metastasis on T2 image (E/T ratio: 7.3±5.4) was larger than that for meningioma (E/T ratio: 1.3±2.2, p<0.001). It seemed that the difference of hypoperfusion area between metastases and meningiomas was due to peritumoral edema. Comparing the peritumoral hypoperfusion volume with edema volume for each tumor group, there were significant differences in both groups (p<0.05, p<0.01). These results suggested that hypoperfusion areas on 3D-SPECT were not only due to reductions of cerebral blood flows in the edematous areas. It should be concluded that the hypoperfusion area was derived mainly from compression from tumor mass in meningiomas. In contrast, the peritumoral hypoperfusion area in metastases was due to reduction in cerebral blood flow in edematous areas and mass effect of peritumoral edema. (author)