The role of 99m Tc-MIBI SPECT/CT in patients with secondary hyperparathyroidism: comparison with 99m Tc-MIBI planar scintigraphy and ultrasonography.

Background: This study aimed to compare the sensitivity of ^99m Tc-MIBI SPECT/CT, ^99m Tc-MIBI planar scintigraphy and ultrasonography (US) in patients with secondary hyperparathyroidism (SHPT), and to explore the factors that affect the sensitivity of ^99m Tc-MIBI SPECT/CT.
Methods: In this retrospective study, forty-six patients with SHPT who underwent ^99m Tc-MIBI planar scintigraphy, ^99m Tc-MIBI SPECT/CT and US were enrolled. They underwent surgery within 1 month. We compared the sensitivity of the different imaging methods based on the lesions according to the pathological results. The parathyroid lesions on ^99m Tc-MIBI SPECT/CT images were divided into missed diagnosis group (MDG) and non-missed diagnosis group (NMDG). We compared the lesion to background ratio (LBR), maximum diameter, volume, the mean CT Hounsfield unit values (CT _mean ) and location of lesions between MDG and NMDG.
Results: The sensitivity of ^99m Tc-MIBI SPECT/CT, ^99m Tc-MIBI planar scintigraphy and US were 70.30% versus 48.48% versus 61.82%, respectively. The sensitivity of ^99m Tc-MIBI SPECT/CT combined US was 79.39%, which was higher than ^99m Tc-MIBI SPECT/CT with significant difference (P = 0.000). On ^99m Tc-MIBI SPECT/CT images, the LBR, maximum diameter and volume of lesions in MDG was smaller than those in NMDG with significant difference (P < 0.001). The average LBR, maximum diameter and volume of lesions in MDG and NMDG were 3.42 ± 1.28, 9.32 ± 2.69 mm, 208.51 ± 163.22 mm ³ versus 6.75 ± 5.08, 15.03 ± 4.94 mm and 863.85 ± 1216.0 mm ³ , respectively.
Conclusions: ^99m Tc-MIBI SPECT/CT exhibited the highest sensitivity among the three methods. When ^99m Tc-MIBI SPECT/CT combined with US, the sensitivity can be further improved. Lesions with lower MIBI uptake and smaller lesions on ^99m Tc-MIBI SPECT/CT images were easily missed.