Detection and Characterization of Parathyroid Adenoma/Hyperplasia for Preoperative Localization: Comparison Between (11)C-Methionine PET/CT and (99m)Tc-Sestamibi Scintigraphy

Abstract

Purpose: (11)C-Methionine PET/CT (Met-PET/CT) is a useful imaging method for detection of parathyroid adenoma; however, the reported detection rate has been variable. The current study was intended to investigate detection sensitivity and preoperative localization of parathyroid adenoma (PA) or parathyroid hyperplasia (PH) on Met-PET/CT compared with (99m)Tc-sestamibi (MIBI) scintigraphy in patients with primary hyperparathyroidism (HPT) or suspected PA.

Methods: Met-PET/CT and MIBI scintigraphy images were reviewed by two nuclear medicine physicians unaware of pathologic results. Detection sensitivities and preoperative localization of detected parathyroid tissues into five predefined segments were evaluated by visual assessment and semi-quantitative analysis with ratio of standardized uptake values (SUVR) between parathyroid tissue and normal lung as reference. Linear regression analysis with SUVR and serum parathyroid hormone (sPTH) was performed for characterization of PA or PH. Predicted PTH (pPTH) was calculated and compared with sPTH in PH and PA. Each pPTH was obtained for a calculated SUVR by using linear regression model from the result of previous linear regression analysis between SUVR and sPTH.

Results: In 16 patients, detection sensitivities of Met-PET/CT and MIBI scintigraphy were 91.7 % (11/12) and 41.7 % (5/12) for PA and PH including both biopsy-confirmed and clinically-suspected cases, and 100 % (8/8) and 50 % (4/8) for pathologically confirmed PA and PH cases only, respectively. Met-PET/CT showed higher performance than MIBI scintigraphy in localization of parathyroid tissues; correct localization rate was 87.5 % (7/8) on Met-PET/CT and 50 % (4/8) on MIBI scintigraphy. In semi-quantitative analysis, SUVR was linearly associated with sPTH by linear regression analysis (sPTH = 39.53 × SUVR - 89.84, p = 0.0383). There was a borderline significant difference in pPTH between PH and PA (35.1 vs 204.7 ± 164.0, p = 0.052), while there was no significant difference in sPTH between PH and PA (289 vs 230.4 ± 160.4, p = 0.305).

Conclusions: Met-PET/CT has a potential to be a useful diagnostic modality for preoperative detection and localization of parathyroid tissues with higher sensitivity than MIBI scintigraphy, and for characterization of PA or PH.

Keywords: 11C-methionine PET/CT; 99mTc-sestamibi scintigraphy; Parathyroid adenoma; Parathyroid hyperplasia; Preoperative localization; Primary hyperparathyroidism.

Fig. 1

Predefined location of parathyroid tissues. Perithyroidal space is divided into four quadrants and paratracheal space is defined as the fifth location

Fig. 2

Representative case of parathyroid adenoma with positive ^99mTc-sestamibi scintigraphy and positive ¹¹C-methionine PET/CT. Parathyroid adenoma is visualized on scintigraphic images at 15 min (a) and 2 h 30 min (b) after intravenous injection of ^99mTc-sestamibi, and fused axial PET/CT image (c) and axial PET image (d) after intravenous injection of ¹¹C-methioinine. The arrow indicates suspicious parathyroid tissue in the right lower quadrant of thyroid gland

Fig. 3

Representative case of parathyroid adenoma with negative ^99mTc-sestamibi scintigraphy and positive ¹¹C-methionine PET/CT. Scintigraphic images at 15 min (a) and 2 h 30 min (b) after intravenous injection of ^99mTc-sestamibi, and fused axial PET/CT image (c) and axial PET image (d) after intravenous injection of ¹¹C-Methioinine. The arrow indicates suspicious parathyroid tissue in the right upper quadrant of thyroid gland

Fig. 4

Correlation between SUVR and sPTH

Fig. 5

Change of sPTH level by application of linear regression model, sPTH = 39.53 × SUVR-89.84. Preoperative sPTH level of PH is not significantly different from that of PA; however, pPTH level of PH is significantly lower than that of PA. It suggests that PH can have lower methionine uptake than PA