Analysis of false-positive and false-negative results in 99mTc-MIBI SPECT/CT parathyroid imaging

Background: Exact preoperative localization is desirable to perform minimally invasive parathyroidectomy for hyperparathyroidism (HPT). This study aimed to evaluate the diagnostic values of Tc-99m-methoxyisobutylisonitrile (Tc-99m-MIBI) single photon emission computed tomography /computed tomography (SPECT/CT) of parathyroid glands by analyzing the relationship between lesion weight and false-negative (FN) results, as well as to explain the possible reason. Methods: The data from 314 patients with suspected HPT who underwent Tc-99m-MIBI SPECT/CT parathyroid imaging between 2011 and 2022 were retrospectively evaluated. The sensitivity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of parathyroid Tc-99m-MIBI SPECT/ CT were calculated, and the false-positive (FP) and FN findings were analyzed. Results: Accurate localization by Tc-99m-MIBI SPECT/CT was significantly associated with the parathyroid hormone (PTH) level. The Tc-99m-MIBI SPECT/CT for diagnosis/lesion location reached a sensitivity of 84.6%/56.8%, a PPV of 97.3%/98.4%, an NPV of only 23.7%/4.18%, and an accuracy of 83.4%/57.1%, respectively. The largest diameter, shortest diameter, and lesion volume were lower in the FN group than in the TP group. A total of 7 FP cases were found, including 2 cases of thyroid nodules, 4 cases of thyroid tissue, and 1 case of hibernoma. A total of 45 FN patients, including 321 FN lesions, were confirmed, of which parathyroid hyperplasia accounted for 97.8%. Lesion weights greater than 20 mu g were able to be detected, but lightweight lesions less than 100 mg were the principal source of FN results, accounting for approximately 39.3%. With lesion weights 0-100, 101-300, 301-1,000, and >1,000 mg, the FN rate was 70.8% (126/178), 51.8% (103/199), 34.6% (81/234), and 8.33% (11/132), respectively. Conclusions: Tc-99m-MIBI SPECT/CT parathyroid imaging provides good sensitivity and high specificity in HPT location. Correct localization by Tc-99m-MIBI SPECT/CT correlates positively with lesion weight and PTH levels. The smaller the lesion, the higher the FN rate in Tc-99m-MIBI SPECT/CT parathyroid imaging, and lesions weighing less than 100 mg are the main source of FN results in Tc-99m-MIBI SPECT/ CT parathyroid imaging.

Automated summary

Tc-99m-MIBI SPECT/CT parathyroid imaging has good sensitivity and high specificity in accurately locating hyperparathyroidism. The accuracy of localization is positively correlated with lesion weight and parathyroid hormone levels. Lightweight lesions are the main source of false-negative results in Tc-99m-MIBI SPECT/CT parathyroid imaging.