The performance of F-18 FCH PET in patients with hyperparathyroidism: Comparing different time-point images

Objectives: F-18 Fluorocholine (F-18 FCH) PET is sensitive for localizing hyperfunctioning parathyroid gland. However, the optimal time point for image acquisition after tracer injection has not been well defined.

Methods: We conducted a prospective study utilizing dual-time-point F-18 FCH PET to pre-operatively localizing hyperfunctioning parathyroid glands. A local ethical committee has approved our research, and all enrolled subjects have given their written consents. We enrolled patients with the diagnosis of hyperparathyroidism and the patient underwent F-18 FCH PET. We acquire PET 5 (early time point) and 60 (late time point) minutes after tracer injection. We also record glandular SUV ratio (SUVR), metabolic volume (MTV) and glandular choline metabolism (TLCM) for analysis. The standard of truth was pathological results after parathyroidectomy.

Results: We enrolled 18 patients and analyzed 62 glandular sites. The lesion based sensitivity of early and late F-18 FCH PET were 72.6% and 68.6%, respectively (p = 0.48). The specificity of early and late F-18 FCH PET were both 81.8%. All true positive lesions on early images were also positive on late images. Among all FCH avid lesions (n = 39), 61.5% (n = 24) glands showed higher SUVR on late images. The glandular weight was correlated with glandular SUVR, MTV and TLCM (ρ= 0.704, 0.469 and 0.565, p < 0.05, respectively, only late image data were shown because of the better correlation). Pre-operative iPTH was not correlated with either glandular weight or semiquantitative PET parameters.

Conclusions: The diagnostic performance of both time point images was not significantly differed, however, based on the SUVR data, if only one time point is allowed, scan acquired 60 mins after tracer injection may be preferred. Also, late image glandular SUVR may be used to predict post-operative glandular weight and maybe more accurate than volumetric parameters.