DUAL-ISOTOPE SPECT OF SKULL-BASE INVASION OF HEAD AND NECK TUMORS

Skull-base invasions of head and neck tumors were examined by simultaneous bone and tumor dual-isotope SPECT (S-SPECT) with Tc-99m-hydroxy-methylene-diphosphonate (Tc-99m-HMDP) and (TI)-T-201-chloride. The effectiveness and reliability of tumor diagnosis by this method was the primary interest in this study. Methods: Before S-SPECT imaging, a phantom experiment using dried skull-bone specimens was performed to establish anatomical details of the skull base with the SPECT camera. Radionuclide crosstalk, window widths and control patients were also examined prior to S-SPECT imaging. Twenty patients with suspected tumor invasion of the skull base underwent S-SPECT. Results: Preliminary experiments revealed that crosstalk effects could be disregarded with adequate window width and routine administrative doses of the radionuclides. S-SPECT detected bone destruction and the extent of tumor invasion for all 12 patients in whom skull-base involvement was diagnosed by CT or MRI. For the three patients in whom CT or MRI revealed no tumor invasion, the S-SPECT images did not show any abnormal accumulation in similar regions. In the remaining five patients without CT and MRI confirmation of skull-base invasion, the S-SPECT findings showed skull-base abnormalities in three. Tumor invasion was confirmed surgically or by clinical follow-up. The remaining two patients had negative S-SPECT images. Conclusion: S-SPECT is an effective and reliable diagnostic technique for detecting tumor invasion in the complex bony regions of the skull base.