Dual-phase planar scintigraphy and early versus delayed SPECT/CT in [99mTc]Tc-MIBI imaging for primary hyperparathyroidism: a blinded comparative study

INTRODUCTION: Accurate preoperative localization of parathyroid adenomas is essential for minimally invasive focused parathyroidectomy inpatients with primary hyperparathyroidism (PHPT). Technetium-99m sestamibi ([99mTc]Tc-MIBI) scintigraphy is routinely performed usinga variety of imaging protocols, including dual-phase planar imaging and single-photon emission computed tomography/computed tomography(SPECT/CT); however, an optimal standardized protocol has not yet been established. This study aimed to directly compare the diagnosticperformance of dual-phase planar scintigraphy, early SPECT/CT, and delayed SPECT/CT for the localization of parathyroid adenomas. MATERIAL AND METHODS: In this retrospective single-center study, 94 examinations in patients with biochemically confirmed PHPT who underwent [99mTc]Tc-MIBI scintigraphy between July 2020 and June 2023 were included. All patients underwent histopathological verification(adenoma or negative findings). Imaging datasets were categorized into three protocols: dual-phase planar imaging, early SPECT/CTat 20 minutes, and delayed SPECT/CT at 120 minutes. Each dataset was independently evaluated by three blinded nuclear medicinephysicians. A scan was considered positive when at least two readers identified a concordant lesion. Sensitivity, specificity, and predictivevalues were calculated with 95% confidence intervals (CIs; Wilson method). Paired comparisons were performed using McNemar's test. RESULTS: Eighty-four of 94 patients (92.7%) were confirmed to have parathyroid adenomas. The sensitivity was 73.8% (95% CI 63.5-82.0%) for dual-phase planar imaging, 78.6% (95% CI 68.6-86.0%) for early SPECT/CT, and 82.1% (95% CI 72.6-88.9%) for delayed SPECT/CT. The corresponding specificity values were 50.0% (95% CI 23.7-76.3%), 60.0% (95% CI 31.3-83.2%), and 50.0% (95% CI 23.7-76.3%), respectively.Delayed SPECT/CT demonstrated significantly greater sensitivity than dual-phase planar imaging (p = 0.01) and early SPECT/CT(p = 0.02), whereas differences in specificity were not statistically significant (p > 0.05). Interobserver agreement was moderate acrossall protocols (κ = 0.40-0.56). CONCLUSIONS: Delayed SPECT/CT provides the highest sensitivity for the preoperative localization of parathyroid adenomas among the evaluated [99mTc]Tc-MIBI protocols. These findings support the inclusion of delayed SPECT/CT as a key component of parathyroid scintigraphy protocols and highlight the need for standardized imaging approaches. Prospective multicenter studies are warranted tovalidate these results.