Functional evaluation of parathyroid adenoma using 99mTc-MIBI parathyroid SPECT/CT

Abstract

In parathyroid adenoma, uptake of technetium-99m-methoxyisobutylisonitrile ((99m)Tc-MIBI) has been suggested to have a correlation with functional markers. The purpose of this study was to evaluate the feasibility of (99m)Tc-MIBI parathyroid single photon emission computed tomography/computed tomography (SPECT/CT) in evaluating the function and disease severity of parathyroid adenoma. Twenty-three patients with surgically confirmed parathyroid adenoma were retrospectively enrolled. A parathyroid planar scan and SPECT/CT were performed before parathyroidectomy. Functional and clinical makers reflecting the disease severity of parathyroid adenoma were also evaluated, including serum intact parathyroid hormone, calcium, bone mineral density, and creatinine clearance. The pathologic volume (V(P)) of the adenoma was measured after parathyroidectomy. On parathyroid SPECT/CT, metabolic volume (V(M)) was measured using an isocontour method. Maximum uptakes of parathyroid adenoma and mean uptakes of contralateral thyroid tissue were measured to calculate the parathyroid adenoma-to-background ratio on parathyroid SPECT/CT (PBR(SCT)) and planar scan (PBR(PL)). V(M) significantly correlated with V(P) (r=0.669, P=0.0005). Serum intact parathyroid hormone level significantly correlated with PBR(PL), PBR(SCT), V(M), and V(P) (P=0.0004, 0.005, 0.003, and 0.025, respectively). However, serum calcium level correlated only with V(M) (P=0.012). Regarding the surgical indication criteria, PBR(SCT) and PBR(PL) were significantly higher in the young-aged group (P=0.0004 and 0.024, respectively) and V(M) was significantly higher in the high calcium level group (P=0.049), whereas V(P) was not different between groups on the basis of any criteria. Quantitative indices of parathyroid SPECT/CT closely correlate with laboratory functional markers and disease severity of parathyroid adenoma. Thus, parathyroid SPECT/CT could be used for evaluation of the underlying functional state and disease severity of parathyroid adenoma, particularly for decision pertaining to surgical treatment.