Background: Current thyroid surgical techniques leave some patients with no remnant tissue, making radioiodine ablation unnecessary. This subgroup can be imaged with I-131 however this can lead to stunning (even at low doses) and suboptimal response to ablative therapy. I-123 can be used but can be expensive and supply problematic. Pertechnetate may be an effective alternative.

Aim: To determine the value of pertechnetate scintigraphy in post-thyroidectomy scanning.

Patients and method: A total of 70 consecutive patients with thyroid cancer were retrospectively reviewed post total-thyroidectomy. Pre-ablative pertechnetate scans were reviewed blindly and then directly compared with post ablation I-131 images. Foci were classified as positive, equivocal or negative.

Results: Of the 70 patients, 68 had uptake on the I-131 study and 2 were negative. On a per patient basis, pertechnetate identified 57/68 patients with I-131 uptake (sensitivity 84%, PPV 97%). On a per site basis, pertechnetate identified 113/166 sites of I-131 uptake (sensitivity 68%, PPV 81%).

Conclusion: Pertechnetate had a reasonable correlation with I-131 on the post ablation scans identifying over 2/3 of all sites with uptake. Pertechnetate scintigraphy had a high PPV thus a positive scan is sufficient to guide progression to ablation therapy in most patients. When the pertechnetate scan is negative, diagnostic imaging with radioiodine may be required.