Value of [11C]-Methionine PET/CT in Preoperative Localization of Parathyroid Adenomas

There are multiple imaging modalities in primary hyperparathyroidism. Ultrasound examination and subtraction scintigraphy are usually the first-line imaging techniques. When these results are negative or inconsistent, additional [11C]-methionine PET/CT (MET-PET/CT) or 4-dimensional computed tomography can be performed. ​This study aims to evaluate MET-PET/CT in comparison with other imaging techniques in primary hyperparathyroidism. This is a retrospective cohort study. Eighty-four patients with primary hyperparathyroidism, who underwent parathyroid surgery, were included. ​Imaging results have been correlated to the perioperative drop in parathyroid hormone level and to the pathological analysis. ​Descriptive statistics are used, supplemented with 95% Clopper–Pearson confidence intervals for sensitivity and specificity and a sub-analysis with the McNemar test on paired data only. The per-lesion sensitivity of MET-PET/CT seems higher than that of [99mTc]-sestamibi or [99mTc]-tetrofosmin and [99mTc]-pertechnetate subtraction scintigraphy. The McNemar test, on paired data only, shows significantly higher sensitivity of MET-PET/CT compared to ultrasound (p=0.039) and significantly higher specificity of ultrasound compared to subtraction scintigraphy (p=0.035).​ MET-PET/CT after inconclusive or negative ultrasound and/or subtraction scintigraphy has an additional value in 70% of the cases.​ Preoperative parathyroid hormone levels were higher in patients in whom MET-PET/CT correctly predicted the pathological parathyroid glands, compared to those where MET-PET/CT missed at least one adenoma. The same trend was seen for 4-dimensional computed tomography. In conclusion, MET-PET/CT seems a valuable imaging modality in primary hyperparathyroidism, at least as second line imaging approach, with a higher per-lesion sensitivity than ultrasound in such setting. Especially when ultrasound and/or subtraction scintigraphy are inconclusive or negative, MET-PET/CT directs the surgeon to the correct localization of the parathyroid adenoma.

Added Value of Subtraction SPECT/CT in Dual-Isotope Parathyroid Scintigraphy

Background: Adding subtraction single-photon emission computed tomography/computed tomography (SPECT/CT) to dual isotope (I-123 and Tc-99m-sestamibi) subtraction parathyroid scintigraphy is not widely implemented. We aimed to assess the added value of dual isotope subtraction SPECT/CT over single isotope SPECT/CT as an adjunct to dual isotope planar pinhole subtraction scintigraphy. Methods: Parathyroid scintigraphies from 106 patients with an estimated total of 415 parathyroid glands who (1) were diagnosed with primary hyperparathyroidism, (2) underwent dual isotope subtraction scintigraphy in the Department of Nuclear Medicine, Gentofte Hospital, Denmark throughout 2017 and (3) underwent subsequent parathyroidectomy, were included. The original dual isotope planar pinhole subtraction plus dual isotope subtraction SPECT/CT (dual/dual method) exams were retrospectively re-evaluated using only Tc-99m-sestamibi SPECT/CT (dual/single method). Statistics were calculated per parathyroid. Surgical results confirmed by pathology served as reference standard. Results: The dual/dual method had higher sensitivity than the dual/single method (82% (95%CI 74%–88%) vs. 69% (95%CI 60%–77%)) while specificity, positive and negative predictive values (PPV and NPV) were similar (specificity 96% vs. 93%, PPV’s 87% vs. 82% and NPV’s 89% vs. 93%). Reader confidence was higher when employing the dual/dual method (p = 0.001). Conclusions: The dual/dual method can be considered superior to the dual/single method in the preoperative imaging in primary hyperparathyroidism.

Bilateral neck exploration in patients with primary hyperparathyroidism and discordant imaging results: a single-centre study

IntroductionFocused parathyroidectomy is the treatment of choice for patients with concordant positive imaging. Bilateral cervical exploration is performed for cases with discordant imaging, yet more than 70% of those cases are the result of a single-gland disease. As focused parathyroidectomy is generally costless and harmless, for cases with discordant imaging, we tried to determine whether preoperative characteristics can lead to a diagnosis of single-gland disease.MethodsThis study included 182 patients treated for primary hyperparathyroidism by bilateral exploration from 2009 to 2012 at La Timone Hospital, Marseille, France. We classified patients based on preoperative images and pathological results (single-gland or multiglandular disease). We then compared the demographical, laboratory and imaging results. We also asked a senior nuclear medicine practitioner who was blind to the ultrasound and pathological results to perform a second reading.ResultsOf the total number of patients, 15.4% had negative, 54.4% discordant and 30.2% concordant imaging. After reviewing the scintigraphy results, 8% of the cases with discordant imaging would have been classified as concordant with ultrasound. Subtraction scintigraphy obtained better results than dual-phase scintigraphy (concordance with ultrasound in 50 vs 31% with classical scintigraphy). For the cases of discordant imaging, no predictive factors of single-gland disease could be identified. Ultrasound and scintigraphy were similarly effective in determining the correct location of the abnormal gland.ConclusionDiscordant results of preoperative imaging modalities do not discriminate between uniglandular and multiglandular diseases in hyperparathyroidism. Diagnostic differentiation between the different causes of hyperparathyroidism requires improvements in imaging techniques and might benefit from subtraction scintigraphy.