Iterative reconstruction: an improvement of technetium-99m MIBI SPET for the detection of parathyroid adenomas?

The purpose of this study was to assess the value of technetium-99m methoxy isobutylisonitrile (MIBI) single-photon emission tomography (SPET) and an i terative reconstruction algorithm for the preoperative localisation of para thyroid adenomas (PTAs). Seventy-two patients (26 male, 46 female, mean age 58+/-16 years) with known primary hyperparathyroidism were examined preope ratively. First, a thyroid examination was performed to detect possible MIB I-accumulating thyroid lesions. Planar scans were then acquired 15 and 120 min and tomographic images 120 min after intravenous injection of 740 MBq T c-99m-MIBI, using a triple-head gamma camera (Picker Prism 3000). Additiona lly, Tc-99m-MIBI/Tc-99m-pertechnetate subtraction scintigraphy of the early planar images was performed. The SPET data were evaluated using an iterati ve reconstruction (multiplicative iterative SPET reconstruction: MISR) as w ell as a standard algorithm (FBP: filtered back-projection with application of a 3-D low-pass postfilter). The weight of the resected PTAs ranged from 110 mg to 5 g. Using planar MIBI scans, correct localisation of the side o f the PTA was possible in 81% of cases (58% for PTAs weighing less than 500 mg). Sensitivity increased to 94% using SPET and FBP, while with MISR it r ose further, to 97%. Patients with PTAs weighing less than 500 mg showed a sensitivity of 88% with MISR and 81% with FBP. Furthermore, there was a cle ar improvement in image quality using MISR. None of the normal parathyroid glands were visualised. This study indicates that, in comparison with plana r scintigraphy, Tc-99m-MIBI SPET is a more sensitive and specific tool for topographical localisation of PTAs, especially those that are small. There is a further improvement in sensitivity and image quality when iterative re construction is used instead of FBP.