Technetium-99m-tetrofosmin uptake in brain tumors by SPECT: comparison with thallium-201 imaging

Thallium-201 is clinically used for the assessment of primary and recurrent brain tumors. The biologic properties of 201Tl that allow it to accumulate within the tumor cells render 201Tl useful in evaluating tumor malignancy, but its physical characteristics and nonroutine availability limits its use in some institutions, as compared to 99mTc-labeled compounds. The aim of this study was to assess the feasibility of using 99mTc-tetrofosmin for imaging brain tumors and to compare its uptake with that of 201Tl.

Twenty-six patients with 27 intracranial masses were studied with SPECT. In the first group of seven patients (Group A), the timing for optimal acquisition of the 99mTc-tetrofosmin scan was assessed. In the second group of 19 patients (Group B), two sequential 201Tl (74-148 MBq intravenous) and 99mTc-tetrofosmin (740-925 MBq intravenous) studies were performed 20 min after tracer injection and compared.

In Group A, no significant difference in the tumor-to-background (T/B) ratio among the 20-, 40- and 120-min postinjection studies was observed. In Group B, the quality of reconstructed images with 99mTc-tetrofosmin, judged visually, was superior to that of 201Tl in 47% of all studies and was comparable in the remaining 53%. A significant relationship between 201Tl and 99mTc-tetrofosmin T/B ratio (r = 0.75, p < 0.01) was found. The T/B ratio of 99mTc-tetrofosmin was significantly higher than that of 201Tl (23.3 +/- 21.5 compared to 6.1 +/- 2.9, p < 0.005).

Technetium-99m-tetrofosmin is a suitable radiotracer for the imaging of intracranial lesions with SPECT. Moreover, a better definition of tumor margins and a higher contrast between neoplastic and normal brain tissue can be achieved.