Dual Tracer 99mTc-Pertechnetate/99mTc-MIBI Dual-Time-Point SPECT/CT Parathyroid Gland Assessment Regarding to Parathyroid Gland Size and Biochemical Parameters – Two Years Single Imaging Centre Experience

Abstract

Introduction: Preoperative parathyroid imaging is inevitable part of focused parathyroid surgery. The aim of our study was assessment of parathyroid scintigraphy diagnostic accuracy regarding to size and metabolic parameters of hyperfunctioning parathyroid tissue. Material and methods: Parathyroid scintigraphy for suspected primary hyperparathyroidism was performed in 95 patients during years 2015 and 2016. Of them, 75 patients with known clinical outcome (40 underwent surgery, 35 had documented laboratory follow-up) were further retrospectively evaluated. The performance of dual tracer 99mTc-pertechnetate and 99mTc-MIBI subtraction and dual-time-point 99mTc-MIBI imaging with SPECT/CT was analysed. Serum parathyroid hormone (PTH), calcaemia, ionized calcaemia and phosphataemia and ultrasound detected adenoma volume and largest diameter in false negative and true positive findings were compared using Mann-Whitney test. Results: Sensitivity and specificity of parathyroid scintigraphy was 74.5% and 95.8%, respectively. NPV was 63.8% and PPV 97.4%. Hyperfunctioning parathyroid tissue detectability was almost significantly associated with hypophosphataemia and PTH levels. Conclusion: Parathyroid scintigraphy provides high sensitivity and superior specificity in parathyroid adenoma location, nevertheless the diagnostic accuracy tends to decline in smaller adenomas and in less metabolically active parathyroid tissue causing only subtle biochemical changes. 18F-Fluorocholine PET/CT or 3D SPECT/CT subtraction should be a reasonable option for those cases.

Factors related to a non‐localising technetium 99m sestamibi scan result during parathyroid adenoma imaging in primary hyperparathyroidism

“…A significant proportion of studies have reviewed biochemical variables including calcium and PTH levels as potential factors localising parathyroid adenomas on 99m Tc‐sestamibi. Our results identified preoperative PTH levels as the only significant factor, with a lower PTH level associated with a higher incidence of a non‐localising 99m Tc‐sestamibi ( P = .034), a finding supported by several other studies 16,22,23 . Furthermore, some studies have identified specific preoperative PTH levels for establishing the outcome of a 99m Tc‐sestamibi scan.…”

“…Our results identified preoperative PTH levels as the only significant factor, with a lower PTH level associated with a higher incidence of a non-localising 99m Tc-sestamibi (P = .034), a finding supported by several other studies. 16,22,23 Furthermore, some studies have identified specific preoperative PTH levels for establishing the outcome of a 99m…”

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

“…Furthermore, there is a difference in imaging criteria; i.e., Asseeva et al discriminate between “uniglandular disease”, “multiglandular disease” and “negative result” while we discriminate by the location of HPGs [ 11 ]. Due to the limited sensitivity of the dual/single method, Krčálová et al recommend adding subtraction SPECT/CT (i.e., dual/dual) or 18F-fluorocholin-positron emission tomography / computed tomography (PET/CT) in order to increase sensitivity [ 14 ]. Others have assessed subtraction pinhole alone and/or subtraction SPECT/CT alone, the former with reported sensitivities and specificities of 75%–88% and 90% respectively, and the latter sensitivity of 86%–95% and specificity 98%–100% [ 6 , 13 ].…”