Performance of F-18 Fluorocholine PET/CT for Detection of Hyperfunctioning Parathyroid Tissue in Patients with Elevated Parathyroid Hormone Levels and Negative or Discrepant Results in conventional Imaging

Abstract

Objective: Our aim was to assess the diagnostic performance of F-18 fluorocholine (FCH) positron emission tomography/computed tomography (PET/CT) in detecting hyperfunctioning parathyroid tissue (HPT) in patients with elevated parathyroid hormone levels with negative or inconclusive conventional imaging results and to compare the findings with those obtained using technetium-99m sestamibi (MIBI) scintigraphy and neck ultrasonography (US).

Materials and methods: Images of 105 patients with hyperparathyroidism who underwent FCH PET/CT, dual-phase MIBI parathyroid scintigraphy (median interval: 42 days), and neck US were retrospectively analyzed. The gold standard was histopathological findings for 81 patients who underwent parathyroidectomy and clinical follow-up findings in the remaining 24 patients. Sensitivities, positive predictive values (PPVs), and accuracies were calculated for all imaging modalities.

Results: Among the 81 patients who underwent parathyroidectomy, either parathyroid adenoma (n = 64), hyperplasia (n = 9), neoplasia (n = 4), or both parathyroid adenoma and hyperplasia (n = 1) were detected, except 3 patients who did not show HPT. Of the 24 (23%) patients who were followed-up without operation, 22 (92%) showed persistent hyperparathyroidism. FCH PET/CT showed significantly higher sensitivity than MIBI scintigraphy and US in detection of HPT (p < 0.01). Sensitivity, PPV, and accuracy of FCH PET/CT were 94.1% (95/101), 97.9% (95/97), and 92.4% (97/105), respectively. The corresponding values for MIBI scintigraphy and US were 45.1% (46/102), 97.9% (46/47), and 45.7% (48/105) and 44.1% (45/102), 93.8% (45/48), and 42.9% (45/105), respectively. Among the 35 patients showing negative MIBI scintigraphy and neck US findings, 30 (86%) showed positive results on FCH PET/CT. FCH PET/CT could demonstrate ectopic locations of HPT in 11 patients whereas MIBI and US showed positive findings in only 6 and 3 patients, respectively.

Conclusion: FCH PET/CT is an effective imaging modality for detection of HPT with the highest sensitivity among the available imaging techniques. Therefore, FCH PET/CT can be recommended especially for patients who show negative or inconclusive results on conventional imaging.

Keywords: Computed tomography; Fluorocholine; Hyperparathyroidism; Parathyroid adenoma; Positron emission tomography; Tc-99m sestamibi.

Fig. 1. Flow chart showing patient selection process.

MIBI = technetium-99m sestamibi, n = number of patients, PTH = parathyroid hormone, US = ultrasonography

Fig. 2. Distribution of concordant and discordant cases between FCH PET/CT and MIBI scintigraphy (A) and neck ultrasonography (B) according to patients' final status based on findings from postoperative histopathological assessments or clinical follow-up examinations.

FCH = fluorine-18 fluorocholine, hPTH = persistent raised PTH, PET/CT = positron emission tomography/computed tomography

Fig. 3. FCH PET/CT (A–C) and MIBI SPECT/CT (D–I) findings for 48-year-old female with hyperparathyroidism (PTH level: 191 pg/mL).

FCH PET (A), CT (B), and fused PET/CT (C) images in FCH PET/CT reveal nodular lesion with intense FCH uptake (arrows) posterior to left thyroid lobe, which was confirmed to be parathyroid adenoma. Patient also showed papillary thyroid microcarcinoma in left thyroid lobe with no FCH uptake. In early MIBI SPECT (D), CT (E), and fused SPECT/CT (F) images, MIBI uptake was noted on left thyroid lobe. Moreover, MIBI uptake persisted in late SPECT (G), CT (H), and fused SPECT/CT (I) images (arrowheads). However, parathyroid lesion posterior to left thyroid lobe did not exhibit any MIBI uptake in early and late SPECT/CT scans (arrows). SPECT = single-photon emission computed tomography

Fig. 4. 39-year-old female patient with hyperparathyroidism (PTH level: 203.0 pg/mL) showing negative MIBI and ultrasonography results (not shown).

FCH PET/CT MIP image (A) shows focus of FCH uptake on upper mediastinum (arrow). Axial PET (B) and fused PET/CT (C) images reveal 1-cm nodular lesion with intense FCH uptake in aortopulmonary window (arrows). Postoperative histopathology revealed presence of ectopic mediastinal parathyroid adenoma. MIP = maximum intensity projection

Fig. 5. 16-year-old female patient with chronic renal failure.

A–F. FCH PET/CT MIP image (A) reveals multiple foci of increased FCH uptake. Axial PET (B) and fused PET/CT (C) images on lower neck region reveal intense FCH uptake on left side that was found to be in accordance with parathyroid adenoma in surgical specimen (arrows). Brown tumors also demonstrate increased FCH uptake (arrowheads). G–L. MIBI SPECT/CT images of same patient. MIBI uptake at late planar (G), SPECT (H), and fused SPECT/CT (I) images reveal MIBI uptake on parathyroid adenoma (arrows). Brown tumors also demonstrate increased MIBI uptake (arrow heads).