The potential value of IVIM MR for radiation-related hypothyroidism in nasopharyngeal carcinoma.

BACKGROUND AND PURPOSE: This study aimed to evaluate the value of intravoxel incoherent motion (IVIM) magnetic resonance (MR) in monitoring radiation-induced thyroid injury and predicting the risk of hypothyroidism (HT) for patients with nasopharyngeal carcinoma (NPC) undergoing intensity-modulated radiotherapy (IMRT).

MATERIALS AND

METHODS

Eligible patients were enrolled and underwent IVIM MR before, halfway through, and upon completion of IMRT. Thyroid function was assessed periodically before and after treatment. The changes in IVIM parameters (D, D*, and f) throughout IMRT and their association with HT were analyzed.

RESULTS

A total of 48 patients were recruited, and 14 (14/48, 29.2 %) developed HT, with a median onset time of 7 months following treatment. 12 of the 45 surviving patients (12/45, 26.7 %) developed HT 1 year after IMRT. The D gradually increased during IMRT (p < 0.001), with the rate of increase in the first half of IMRT significantly greater than that in the second half (9.50 % vs. 0.94 %, p = 0.003). The D* initially increased and subsequently decreased during IMRT (p = 0.036). Female, N3 stage, and ΔDhalf(%) were identified as independent risk factors for HT 1 year after IMRT. A nomogram was developed with favorable performance and accuracy.

CONCLUSIONS

A high incidence of HT with a short latency period is still observed in NPC. When formulating IMRT plan for female or N3 stage NPC, efforts should be made to minimize the thyroid exposure. IVIM MR shows promise as a tool for dynamically monitoring radiation-related thyroid injury, with ΔDhalf(%) demonstrating potential for early prediction of HT 1 year after IMRT.