The role of fusion images of Tl-201 SPECT and enhanced CT in assessment of efficacy in percutaneous ethanol injection (PEI) in benign thyroid nodules

Objectives To determine whether 2D and 3D fusion images of Tl-201 SPECT and CT is valuable in evaluation of PEI for benign thyroid nodules.

Methods 57 patients with cytologically proven benign nodules with 3-5 cm in the longest diameter were enrolled. PEI was performed as a fractionated session using multi-insertion technique. After local anesthesia, absolute ethanol was selectively injected within the nodule under the guidance of a 12MHz ultrasound probe. Session was repeated 4-6 times until the vascular signal in the nodule on Doppler US disappeared. Combined study of Tl-201 SPECT and CT were repeatedly performed before and at the end of PEI session. Thin-slice MPF images of the neck were obtained using a 64-row MDCT with enhancement . 2D and 3D fusion images of Tl-SPECT and volume rendering images of thyroid containing superior thyroid artery were obtained using dedicated workstation.

Results Based upon findings of fusion images of 2nd study, patients were assigned to either of the following subgroups; A) complete disappearance of Tl uptake with discontinuation of superior thyroid artery supply into nodule (n=29). B) either persistent Tl uptake or residual blood supply from superior thyroid artery followed by with or without additional ethanol injection (n=28). Volume reduction rates(%) of the nodule at 4 months after PEI in group A and B were 79± 10.0 and 66±11.5, respectively Patients were followed up for 18 months or longer. During the followup period, only 2 (7%) of group A showed re-growth of the treated nodule while 10 (37%) in the group B showed re-growth of the treated nodule. There was statistical difference in tumor regression rate and tumor re-growth between Group A and B.

Conclusions Fusion images of Tl-201 SPECT and CT are highly useful in optimal evaluation of efficacy of PEI in benign thyroid nodules. Disappearance of Tl uptake associated with discontinuation of feeding artery indicates successful outcome of PEI with high prevalence