percutaneous microwave ablation of thyroid nodules: efficacy evaluation with 99m tc - pertechnetate and 99mtc-mibi functional imaging

background: local ablative treatments play an important role for patients who cannot be treated surgically. radiofrequency ablation is a well-established alternative to surgical treatment of thyroid nodules, however it also has disadvantages. microwave ablation (mwa) is a new minimally invasive treatment promising several improvements. the aim of this retrospective study was to evaluate the effects of microwave ablation on thyroid nodules by 99mtc-pertechnetate and 99mtc-mibi scintigraphy. materials and methods: 30 patients with overall 40 nodules were treated. for the ablation of thyroid nodules, a microwave generator working with frequencies from 902 to 928 mhz was used. the ablation time ranged between 120 and  300 seconds per ablation zone. the target temperatures ranged between 60-80 °c. pre- and post- interventional, the radionuclide uptake was determined using a thyroid specific scintillation camera. for 27 cold nodules 99mtc-mibi was used for evaluation; 13 indifferent nodules were measured with 99mtc-pertechnetate. results: the relative change of uptake was detected as a quotient of pre- and post- therapeutic uptake. the statistical analysis of scintigraphy data proved the efficacy of microwave ablation. 99mtc-pertechnetate scintigraphy  showed an uptake reduction of 39% (range 9 to 85%). 99mtc-mibi imaging showed a median reduction of 40% (p<0.01) (range 7 to 100%). conclusion: the determined results show the effectiveness of mwa as a treatment option for benign thyroid nodules. with functional scintigraphy a significant activity decrease could be detected in the ablation zone; hence a verification of affectivity was possible after a short period of time.