A Pilot Comparison of 18F-fluorocholine PET/CT, Ultrasonography and 123I/99mTc-sestaMIBI Dual-Phase Dual-Isotope Scintigraphy in the Preoperative Localization of Hyperfunctioning Parathyroid Glands in Primary or Secondary Hyperparathyroidism: Influence of Thyroid Anomalies

Abstract

We compared (18)F-fluorocholine hybrid positron emission tomography/X-ray computed tomography (FCH-PET/CT) with ultrasonography (US) and scintigraphy in patients with hyperparathyroidism and discordant, or equivocal results of US and (123)I/(99m)Tc-sesta-methoxyisobutylisonitrile (sestaMIBI) dual-phase parathyroid scintigraphy. FCH-PET/CT was performed in 17 patients with primary (n = 11) lithium induced (n = 1) or secondary hyperparathyroidism (1 dialyzed, 4 renal-transplanted).The reference standard was based on results of surgical exploration and histopathological examination. The results of imaging modalities were evaluated, on site and by masked reading, on per-patient and per-lesion bases.In a first approach, equivocal images/foci were considered as negative. On a per-patient level, the sensitivity was for US 38%, for scintigraphy 69% by open and 94% by masked reading, and for FCH-PET/CT 88% by open and 94% by masked reading. On a per-lesion level, sensitivity was for US 42%, for scintigraphy 58% by open and 83% by masked reading, and for FCH-PET/CT 88% by open and 96% by masked reading. One ectopic adenoma was missed by the 3 imaging modalities. Considering equivocal images/foci as positive increased the accuracy of the open reading of scintigraphy or of FCH-PET/CT, but not of US. FCH-PET/CT was significantly superior to US in all approaches, whereas it was more sensitive than scintigraphy only for open reading considering equivocal images/foci as negative (P = 0.04). FCH uptake was more intense in adenomas than in hyperplastic parathyroid glands. Thyroid lesions were suspected in 9 patients. They may induce false-positive results as in one case of oncocytic thyroid adenoma, or false-negative results as in one case of intrathyroidal parathyroid adenoma. Thyroid cancer (4 cases) can be visualized with FCH as with (99m)Tc-sestaMIBI, but the intensity of uptake was moderate, similar to that of parathyroid hyperplasia.This pilot study confirmed that FCH-PET/CT is an adequate imaging tool in patients with primary or secondary hyperparathyroidism, since both adenomas and hyperplastic parathyroid glands can be detected. The sensitivity of FCH-PET/CT was better than that of US and was not inferior to that of dual-phase dual-isotope (123)I/(99m)Tc-scintigraphy. Further studies should evaluate whether FCH could replace (99m)Tc-sestaMIBI as the functional agent for parathyroid imaging, but US would still be useful to identify thyroid lesions.

FIGURE 1

Primary hyperparathyroidism (patient ^#6). A, FCH-PET and PET/CT fused images (MIP, coronal and transversal slices, summed dynamic images in the left column, upper static images in the right column): focus evocative of a left inferior hyperfunctioning parathyroid gland, better visible on the static images. B, ¹²³I/^99mTc-sestaMIBI scintigraphy: discrete focus evocative of a left inferior hyperfunctioning parathyroid gland. On postsurgical histology, a 0.3 g adenoma was found. PTH serum levels decreased from 70 pg/mL preoperatively to 4 pg/mL on the day after surgery. FCH-PET/CT = ¹⁸F-fluorocholine hybrid positron emission tomography/X-ray computed tomography; PTH = parathyroid hormone; sestaMIBI = sesta-methoxyisobutylisonitrile.

FIGURE 2

Secondary hyperparathyroidism in a dialysed patient (patient #13). A, FCH-PET and PET/CT fused images (MIP, coronal and 3 levels of transversal slices, summed dynamic images in the left column, upper static images in the right column): foci evocative of P3, P4 right, and P3 left hyperfunctioning parathyroid glands, visible on both dynamic and static images. B, ¹²³I/^99mTc-sestaMIBI scintigraphy: foci evocative of the same 3 hyperfunctioning parathyroid glands. On postsurgical histology, three 0.1 g hyperplastic parathyroid glands corresponding to those foci were found. PTH serum levels decreased from 1946 pg/mL preoperatively to 146 pg/mL on the day after surgery. FCH-PET/CT = ¹⁸F-fluorocholine hybrid positron emission tomography/X-ray computed tomography; sestaMIBI = sesta-methoxyisobutylisonitrile.

FIGURE 3

Persistent secondary hyperparathyroidism in a patient after renal transplantation (patient #16). A, FCH-PET and PET/CT fused images (MIP, coronal and 3 levels of transversal slices, summed dynamic images in the left column, upper static images in the right column): foci evocative of P3, P4 right, and P3 left hyperfunctioning parathyroid glands, identified only on the static images. B, ¹²³I/^99mTc-sestaMIBI scintigraphy: discrete focus evocative of a right inferior hyperfunctioning parathyroid gland; on open reading, another discrete focus evocative of a right inferior hyperfunctioning parathyroid gland was also mentioned. On postsurgical histology, three hyperplastic parathyroid glands corresponding to the FCH foci were found, their weight ranging from 0.1 to 0.3 g. PTH serum levels decreased from 167 pg/mL preoperatively to 70 pg/mL on the day after surgery. FCH-PET/CT = ¹⁸F-fluorocholine hybrid positron emission tomography/X-ray computed tomography; PTH = parathyroid hormone; sestaMIBI = sesta-methoxyisobutylisonitrile.

FIGURE 4

Lithium-induced hyperparathyroidism (patient #12). A, FCH-PET and PET/CT fused images (MIP, coronal and transversal slice, early dynamic image in the left column, upper static images in the right column): a large focus with early and intense uptake extending over the thyroid isthmus and the adjacent part of the thyroid left lobe (thyroid nodule or hyperfunctioning parathyroid gland?). B, ¹²³I/^99mTc-sestaMIBI scintigraphy: similar focus corresponding to an iodine-negative part of the thyroid gland. By discontinuing lithium therapy, PTH serum levels decreased from 165 pg/mL to 90 pg/mL at the time of PET/CT and to 40 pg/mL on the day after surgery. This focus actually corresponded to a large oncocytic adenoma and a smaller follicular adenoma of the thyroid. Four small bilateral lesions of thyroid carcinoma with lymph nodes metastases were discovered at histology (all < 2 mm in size), but no abnormal parathyroid gland. FCH-PET/CT = ¹⁸F-fluorocholine hybrid positron emission tomography/X-ray computed tomography; PTH = parathyroid hormone; sestaMIBI = sesta-methoxyisobutylisonitrile.