Respiratory gating in [18F]fluorocholine PET/CT for hyperparathyroidism: a quantitative proof-of-concept study

The effect of breathing on the [¹⁸F]fluorocholine parathyroid uptake profile has not been yet evaluated. The main objective of our study is to assess the technical feasibility of respiratory-gated [¹⁸F]fluorocholine PET/CT in patients with hyperparathyroidism. Specifically, we aimed to investigate whether respiratory motion correction has a measurable impact on quantitative PET parameters compared to free-breathing PET in a cohort of patients with clearly identifiable hypermetabolic parathyroid lesions.

Respiratory-gated [¹⁸F]fluorocholine PET/CT was performed using a pressure-sensitive belt placed around the thorax. An elliptic volume of interest was drawn on each hyperfunctioning parathyroid on both respiratory-gated and free-breathing PET scans, and SUVmax and SUVpeak were measured. An image profile was drawn across hypermetabolic targets on the coronal view, and full-width-at-half-maxima (FWHM) of glandular uptake profile was calculated. Wilcoxon signed-rank test and Mann-Whitney U-test were used for intragroup and intergroup comparison, respectively. A P value <0.05 was considered as significant.

A total of 143 hyperfunctioning parathyroid glands (61 superior, 79 inferior, three ectopic) were identified in 110 patients. Respiratory-gated PET showed a statistically significant increase in both SUVmax and SUVpeak compared to ungated PET across all glands (P<0.001). The effect was more pronounced for inferior glands, with a mean SUVmax increment of 10.14%, compared to 7.81% for superior glands, although the difference was not statistically significant for the latter. The mean extent of respiratory parathyroid blurring in the axial direction was 13.7 mm. FWHM analysis revealed a significant reduction in respiratory blurring in respiratory-gated PET (P<0.001).

Respiratory gating improves image quality and visual assessment of hyperfunctioning parathyroid glands by reducing image blurring. Further research is necessary to assess the diagnostic impact of these findings in clinical practice, especially in cases with indeterminate ungated [¹⁸F]Fluorocholine PET examinations.