We have previously demonstrated the role of high-resolution ultrasonography (US) in preoperative localization of parathyroid adenoma in patients with primary hyperparathyroidism (PHPT) and no thyroid abnormalities. The present study prospectively evaluated the possible additional value of 99mTc-sestamibi (MIBI) in patients with PHPT and concomitant multinodular thyroid disease (MND). Patients with PHPT underwent US and MIBI scintigraphy prior to neck exploration. Imaging data were correlated with the site and pathology of the parathyroid tissue removed and were analyzed separately for patients with MND and those with a normal thyroid gland. Among 77 patients with a solitary parathyroid adenoma at surgery, 40 had concomitant MND, whereas 37 patients had no morphologic changes in the thyroid gland, on US or at surgery. Prior to surgery, MIBI scintigraphy depicted 58 of the 77 adenomas (75%) and US localized 51 (66%): the combined sensitivity was 87% (67/77). Among the 37 patients with no thyroid nodules, MIBI located 29 (78%) and US identified 30 (81%) of the adenomas; the combined sensitivity was 89%. In the 40 patients with MND, MIBI identified 29 adenomas (73%) and US localized only 53% (21/40); the combined sensitivity was 85%. Overall, the positive predictive value (PPV) of MIBI for detecting a solitary parathyroid adenoma was 94%, for US it was 88%, and with the two tests combined it was 97%. In patients with no thyroid abnormalities, the PPV of MIBI and US was 97%, but it decreased to 91% and 78%, respectively, in patients with MND. Two patients with false-positive findings on both MIBI and US had associated thyroid disease. Hence MIBI scintigraphy contributes to localization of a solitary parathyroid adenoma mainly in patients with concomitant MND. The combined MIBI and US modalities result in sparing these patients bilateral neck exploration.

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Radiation doses to one PET technologist performing 100 18F FDG (18F fluorodeoxyglucose) imaging procedures were measured in a clinical setting using two types of thermoluminescent dosimeter (TLD) badges, one finger-ring TLD and one electronic pocket dosimeter (EPD). 18F FDG was handled either with unshielded or with viewing window tungsten shielded syringes. The resulting doses using unshielded syringes were 13.8 +/- 0.8 microSv/370 MBq and 14.3 +/- 0.4 microSv/370 MBq, measured with TLD 100 and with TLD 700H/600H, respectively. For the same series of measurements, the doses obtained using shielded syringes were 10.7 +/- 0.4 microSv/370 MBq and 7.2 +/- 2.1 microSv/370 MBq with TLD700H/600H and with EPD, respectively. The dose to the right hand from shielded syringes was 69.3 +/- 5.5 microSv/370 MBq. All these values are within the ICRP recommended dose limits. Extrapolated to 725 examinations per year, the resulting effective dose measured with TLD would be 10 mSv with unshielded and 7.5 mSv with shielded syringes, respectively (25% dose reduction). The doses measured by TLD were consistently higher than those measured by EPD, suggesting that EPD measurements might underestimate occupational doses.