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Recombinant human thyrotropin (rhTSH) significantly changes the distribution of ¹²⁴I and ¹⁸FDG on PET-CT scans in patients with nontoxic nodular goiter

¹ Nuclear Medicine, Catharina Hospital Eindhoven, Eindhoven, Netherlands

1503

Objectives: Earlier, we demonstrated that the heterogeneous distribution of ¹²³I in planar scans of nontoxic, nodular goiters is changed by 0.03 mg rhTSH. Now, using PET-CT, we aimed to quantify and compare the 3D distribution of ¹⁸FDG, another interesting metabolic tracer, and ¹²⁴I within nodular goiters, and to establish their respective levels of stimulation of uptake after rhTSH.

Methods: 10 adult patients, referred for ¹³¹I therapy for nontoxic nodular goiter, underwent two PET-CT scans of the cervical region, 1h after administration of 18 MBq ¹⁸FDG and 24h after oral administration of 15 MBq ¹²⁴I. At least 2 wk later, the same scans were repeated 24h after 0.03 mg rhTSH i.m.. After dividing the thyroid into 6x6x6 mm VOIs, Normalized Count Ratios (NCR; comparing uptake VOI with uptake entire thyroid; see abstract A. Reijnders) were computed for each VOI. NCR was plotted against %VOI-count for each pairwise comparison. Weighted linear regression analysis was applied to analyze linear trends. Parametric NCR images were produced.

Results: NCR parametric images showed different baseline distributions of ¹²⁴I and ¹⁸FDG and local differences in levels of stimulation of ¹²⁴I and ¹⁸FDG uptake by rhTSH. Three plots of NCR vs %VOI-count showed a negative slope. Baseline ¹⁸FDG vs baseline ¹²⁴I: average slope -0.069 (P<0.02; n=10); stimulated vs baseline ¹²⁴I: average slope -0.007 (P<0.01; n=10), stimulated vs baseline ¹⁸FDG: average slope -0.005 (P<0.03; n=6).

Conclusions: Baseline ¹²⁴I and ¹⁸FDG distribution in nodular goiters differ significantly. rhTSH stimulates ¹²⁴I and FDG uptake most in areas with low baseline uptake, thereby decreasing the heterogeneity of uptake. Areas with most stimulation by rhTSH in ¹²⁴I and ¹⁸FDG scans do not correspond.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Huysmans, D. Articles by Arends, B. PubMed Articles by Huysmans, D. Articles by Arends, B.