Comparison between MIBI-based radiopharmaceuticals for parathyroid scintigraphy: quantitative evaluation and correlation with clinical-laboratory parameters.

OBJECTIVE: Parathyroid scintigraphy is mandatory for the identification of hyperfunctioning parathyroid glands in hyperparathyroidism (HPT). The use of 99mTc-methoxy-isobutyl-isonitrile (MIBI) as radiopharmaceutical for parathyroid scintigraphy is considered the most valid and useful considering its uptake mechanism. Several MIBI-based radiopharmaceuticals are commercially available (i.e., MediMIBI, TechneMIBI, Stamicis). They seem to have similar physico-chemical characteristics and the choice between them is based on commercial criteria, even though some differences in qualitative scintigraphic results have been appreciated. Aims of the study were: first, to compare the scintigraphic quantitative data of MediMIBI, TechneMIBI, and Stamicis, particularly in the view of a personalized medicine approach; second, to investigate the potential effect of clinical-laboratory data on image quality using one of these radiopharmaceuticals. METHODS: Patients with diagnosis of HPT, who underwent a parathyroid scintigraphy using one of the three MIBI-based radiopharmaceuticals between December 2018 and October 2020, have been retrospectively identified. Parameters derived from regions of interest (ROIs) drawn on three different sites were obtained: a reasonable parathyroid lesion detected, an area in the lateral neck considered as the background, and the hepatic dome as the site of MIBI physiological uptake. Laboratory and clinical data, such as serum calcium, PTH, vitamin D, and creatinine levels, as well as possible drug-mediated interferences were considered. RESULTS: Among 250 patients included, 83 (33.2%) had the parathyroid scintigraphy using MediMIBI, 84 (33.6%) using TechneMIBI and 83 (33.2%) using Stamicis. The ROIs on the parathyroid uptake at early images, on the background, and on the hepatic dome were statistically different among the three groups (p < 0.05). No significant differences were found in the remaining semi-quantitative parameters among the three groups, not even considering clinical-laboratory data. CONCLUSIONS: Some differences in semi-quantitative parameters emerged among MIBI-based radiopharmaceuticals for parathyroid scintigraphy. This might justify the different qualitative scintigraphic results obtained using one or another of the cited radiopharmaceuticals.

Characterisation of a ß detector on positron emitters for medical applications.

PURPOSE: Radio Guided Surgery (RGS) is a technique that helps the surgeon to achieve an as complete as possible tumor resection, thanks to the intraoperative detection of particles emitted by a radio tracer that bounds to tumoral cells. In the last years, a novel approach to this technique has been proposed that, exploiting ß- emitting radio tracers, overtakes some limitations of established γ-RGS. In this context, a first prototype of an intraoperative ß particle detector, based on a high light yield and low density organic scintillator, has been developed and characterised on pure ß- emitters, like 90Y. The demonstrated very high efficiency to ß- particles, together with the remarkable transparency to photons, suggested the possibility to use this detector also with ß+ emitting sources, that have plenty of applications in nuclear medicine. In this paper, we present upgrades and optimisations performed to the detector to reveal such particles. METHODS: Laboratory measurement have been performed on liquid Ga68 source, and were used to validate and tune a Monte Carlo simulation. RESULTS: The upgraded detector has an ~80% efficiency to electrons above ~110keV, reaching a plateau value of ~95%. At the same time, the probe is substantially transparent to photons below ~200keV, reaching a plateau value of ~3%. CONCLUSIONS: The new prototype seems to have promising characteristics to perform RGS also with ß+ emitting isotopes.

Parathyroid scintigraphy in primary hyperparathyroidism: comparison between double-phase and subtraction techniques and possible affecting factors.

PURPOSE: Parathyroid scintigraphy is superior to other imaging techniques in detecting hyperfunctioning parathyroid glands. It is mainly performed using double-phase or dual-tracer subtraction methods. Neither of the techniques is perfect and different protocols are being used. We aimed to evaluate the accuracy of double-phase and subtraction methods in detecting abnormal gland as well as the potential effects of coexisting thyroid disease and clinical-laboratory data. METHODS: We considered patients with primary hyperparathyroidism who underwent parathyroid surgery, after a parathyroid scintigraphy between April 2015 and February 2017. Sixty-eight patients were included; in 45 cases (66.2%), a thyroid disease was coexistent. Diagnostic performances of the two techniques were compared. The effect of thyroid disease and clinical-pathological data on examination interpretation was considered. RESULTS: Double-phase scintigraphy showed higher sensitivity and accuracy in detecting the exact abnormal gland compared to the digital subtraction (90% and 75% vs. 76% and 66%, respectively). For double-phase technique, sensitivity and accuracy were higher in cases with no thyroid disease when compared to those with thyroid disease (92% and 86% vs. 88% and 69%, respectively). Similarly, for digital subtraction, sensitivity and accuracy were higher in the absence of thyroid disease compared to their presence (84% and 79% vs. 70% and 58%, respectively). There was no significant variation in the performance of both techniques, considering clinical-laboratory data. CONCLUSIONS: Double-phase scintigraphy has been more accurate than digital subtraction. The presence of thyroid disease could be a possible limit, affecting the subtraction more than the double-phase technique. Clinical data did not influence the scintigraphic outcome.

Bilateral adrenalectomy: a review of 10 years' experience.

INTRODUCTION The 2012 British Association of Endocrine and Thyroid Surgeons audit report showed that only 86 of 1359 patients who underwent adrenalectomy had a bilateral operation; thus the experience with this procedure remains limited. METHODS Retrospective review of patients undergoing bilateral adrenalectomy in a tertiary referral centre. RESULTS Between November 2005 and January 2016, bilateral adrenalectomy was performed in 23 patients (6 male, 17 female, age 43 ± 4 years) diagnosed with Cushing's disease (n = 13), hereditary phaeochromocytomas (n = 6), adrenocortical cancer (n = 2), colorectal metastatic disease (n = 1) and adrenocortical adenomas (n = 1). A laparoscopic transperitoneal approach was used in 17 patients, with one conversion to open. Three patients had open adrenalectomies for adrenocortical cancer and for simultaneous phaeochromocytomas and pancreatic neuroendocrine tumours in a patient with Von Hippel-Lindau syndrome. Three patients with Cushing's had a bilateral retroperitoneoscopic operation. The mean operating time was 195 ± 16 minutes for laparoscopic operations (n = 16), 243 ± 44 minutes for open adrenalectomies (n = 4) and 151 ± 12 minutes for retroperitoneal operations. It was significantly shorter for Cushing's disease than for phaeochromocytomas (162 ± 8 vs. 257 ± 39 minutes, P < 0.01). Median length of hospital stay was 5 days. Postoperative complications (Clavien-Dindo classification) included one chest infection (level 2), one postoperative haemorrhage and two chest drains for pneumothorax (level 3), two postoperative cardiac arrests (level 4) and one late cancer death from complications related to uncontrolled hypercortisolism (level 5). DISCUSSION Synchronous bilateral adrenalectomy remains an infrequent operation. The laparoscopic approach is feasible in the majority of patients. It is likely that the retroperitoneoscopic adrenalectomy will become the standard approach for bilateral operations.

Calcitonin measurement in fine-needle aspirate washouts vs. cytologic examination for diagnosis of primary or metastatic medullary thyroid carcinoma.

Ultrasound-guided fine-needle aspiration biopsy cytology (FNAB-C) is able to detect approximately 63% of medullary thyroid carcinoma (MTC). The measurement of calcitonin in the needle washout (FNAB-CT) could improve its accuracy. Sixty-two FNAB-C were performed in 38 patients. Serum calcitonin (sCT) was measured before performing FNAB-C. After obtaining a FNAB-C specimen, the needle was washed with 0.5 ml of saline solution to obtain the CT washouts. Receiver operating characteristic (RO C) analysis identified the cut-offs of FNAB-CT and FNAB-CT/sCT. Eighteen MTC were found at final histology. RO C analysis indicated FNAB-CT > 10.4 pg/ml and FNABCT/ sCT > 1.39 as more accurate cut-off values. Overall accuracy, positive (PPV) and negative predictive values (NPV) were 85%, 100 and 83%, respectively, for FNAB-C, 97%, 100%, 96% for FNAB-CT and 90%, 83% and 93% for FNAB-CT/sCT. The integration of FNAB-C and FNAB-CT resulted in 98% overall accuracy, 100% PPV and 98% NPV; the integration of FNAB-C and FNAB-CT/sCT in 90% overall accuracy, 80% PPV and 95% NPV. One of 2 false negative FNAB-CT and one of 3 false negative FNAB CT/sCT were correctly diagnosed by FNAB-C. Eight of 9 non-diagnostic FNAB-C were correctly classified by FNAB-CT and 7 by FNAB CT/sCT. FNAB-CT should integrate but not replace FNAB-C. FNAB-CT is particularly useful in the presence of non-diagnostic FNAB-C.