Effect of early multiple acid stimulation on salivary gland Tc-99m pertechnetate uptake: a prospective study

Salivary gland dysfunction is a common side effect of radioiodine-131 (ˆ131I) therapy for differentiated thyroid cancer (DTC). We hypothesized that early repeated acid stimulation during Tc-99m salivary gland scintigraphy would reduce radioactive tracer accumulation in salivary glands.

Eighty-one post-thyroidectomy patients with DTC were assigned to three equal groups: control (no acid stimulation), single stimulation at 2 h post-injection, and early repeated stimulation every 30 min after Tc-99m Pertechnetate (^99mTcO₄^-) injection. ^99mTcO₄^- salivary gland scintigraphy was performed with regions of interest delineated for bilateral parotid and submandibular glands. Time-activity curves were generated over 2.5 h, and radioactivity counts and accumulation ratios were calculated at defined intervals.

Baseline parotid and submandibular radioactivity counts did not differ significantly across groups (parotid: P > 0.05; submandibular: P > 0.05). Both acid stimulation protocols induced significant reductions in glandular radioactivity compared with control at all dynamic acquisition intervals (P < 0.001). Cumulative tracer accumulation was significantly lower in the early repeated stimulation group versus the control and single-stimulation groups (P < 0.001). At the same time, no significant difference was observed between control and single-stimulation groups.

Early repeated acid stimulation markedly decreases ^99mTcO₄^- uptake and retention in salivary glands, outperforming delayed single stimulation.

Implementing early repeated acid stimulation during 131I therapy may help prevent salivary gland injury and preserve gland function in DTC patients.