Renal hyperparathyroidism: preoperative detection of abnormal parathyroid glands by 18F-fluorocholine PET/CT and ultrasonography. Comparison of diagnostic performance and optimization of imaging sequence based on 159 paired examinations.

BACKGROUND

A non-invasive location of the abnormal parathyroid glands (PT) is recommended, by pairing ultrasonography (US) with a functional imaging modality, the most accurate being 18F-fluorocholine (FCH) PET/CT. Limited evidence is available about optimization of presurgical imaging in renal hyperparathyroidism (rHPT). We performed a head-to-head comparison of the detection of abnormal parathyroid glands pairing those two imaging modalities in this context. We also investigated whether awareness of the results of the examination carried out first improved the sensitivity of the interpretation of the second examination, aiming to determine the most effective sequence for performing those paired examinations (PEs).

METHODS

FCH PET/CT has been performed as part of presurgical work-up for rHPT in one single PET center, paired with ultrasonography (US) (PE: paired examinations), without predefined sequence order, in a real-world context. Were selected from our database 159 PEs performed between September 2012 and September 2022. PET/CT was acquired 20-30 min after FCH injection of 3 MBg/kg body mass; US was performed from the angle of the mandible to the mediastinum with a high-frequency linear probe and a microconvex probe for deep structures. The interpretation reports have been carried out-on site after each examination, aware of the elements of the patient's file, including the result of the 1st PE for interpreting the 2nd PE. Each abnormal focus or image was rated as positive or equivocal for an abnormal parathyroid gland (PT), or of another origin. The positivity rate was determined for each imaging modality. We were aware of PT (re)operation after 98 PEs; 227 abnormal PTs were resected, histology being the standard-of-truth to determine the gland-based sensitivity. The Fisher's Test was used to compare the gland-based sensitivity of each imaging modality, according to being performed first or second.

RESULTS

The patient-based positivity rate of FCH PET/CT was greater than that of US (P<0.0001), equivocal foci or images being considered either as negative (91% vs. 64% respectively) or as positive (92% vs. 69%). Accordingly, the gland-based sensitivity of FCH PET/CT was also greater than that of US (P<0.0001), equivocal foci or images being considered either as negative (85% vs. 58%, respectively) or as positive (89% vs. 62%, respectively). Interestingly, the diagnostic performance of US was significantly greater if practiced and interpreted aware of FCH PET/CT results (gland-based sensitivity, equivocal images considered as negative: 50% US 1st vs. 74% US 2nd after FCH PET/CT, P<0.0006). For FCH PET/CT, the difference was not significant.

CONCLUSIONS

This is currently the largest of published series about preoperative imaging with FCH PET/CT in rHPT. Our results confirmed superior gland-based sensitivity of FCH PET/CT and also substantiated performing US after FCH PET/CT, whose results can guide US practice and interpretation, both PEs contributing for an optimal surgical protocol. We conclude that optimal imaging sequence in rHPT is FCH PET/CT performed first and not just part of the first line imaging examinations.