Value of 123I/99mTc-sestamibi parathyroid scintigraphy with subtraction SPECT/CT in primary hyperparathyroidism for directing minimally invasive parathyroidectomy.

BACKGROUND: Primary hyperparathyroidism/(PHPT) is one of the most common endocrinological conditions. Surgery remains the only curative option. We have evaluated the performance of double isotope 123I/99mTc-sestamibi parathyroid scintigraphy/(PS) with subtraction SPECT/CT in PHP for identifying uniglandular disease. METHODS: Ninety PHPT patients undergoing parathyroidectomy (December 2015-August 2016) were included. All patients were evaluated with neck ultrasound/(US), PS and SPECT/CT with a new protocol. Outcomes from imaging modalities were reported as: uniglandular disease/(UGD), multiglandular disease/(MGD), or negative, and were compared to post-operative diagnoses. RESULTS: Post-operatively, 72 and 18 patients had true UGD and MGD, respectively. Sensitivities and specificities of US, pinhole scintigraphy with subtraction, pinhole and SPECT/CT with subtraction, and all modalities combined were 91.7%/38.9%, 88.9%/72.2%, 93%/66.7% and 84.72%/77.78%, respectively: specificity of US + PS superior to US alone, p = 0.074. SPECT/CT enables reclassification of doubtful uptake foci. CONCLUSIONS: Combination of neck US and PS with subtraction SPECT/CT offers a higher specificity for guiding towards minimally invasive parathyroidectomy.

Determination of the unmetabolised (18)F-FDG fraction by using an extension of simplified kinetic analysis method: clinical evaluation in paragangliomas.

Tumours with high (18)F-FDG uptake values on static late PET images do not always exhibit high proliferation indices. These discrepancies might be related to high proportion of unmetabolised (18)F-FDG components in the tissues. We propose a method that enables to calculate different (18)F-FDG kinetic parameters based on a new mathematical approach that integrates a measurement error model. Six patients with diagnosed non-metastatic paragangliomas (PGLs) and six control patients with different types of lesions were investigated in this pilot study using (18)F-FDG PET/CT. In all cases, a whole-body acquisition was followed by four static acquisitions centred over the target lesions, associated with venous blood samplings. We used an extension of the Hunter's method to calculate the net influx rate constant (K H). The exact net influx rate constant and vascular volume fraction (K i and V, respectively) were subsequently obtained by the method of least squares. Next, we calculated the mean percentages of metabolised (PM) and unmetabolised (PUM) (18)F-FDG components, and the times required to reach 80 % of the amount of metabolised (18)F-FDG (T80%). A test-retest evaluation indicated that the repeatability of our approach was accurate; the coefficients of variation were below 2 % regardless of the kinetic parameters considered. We observed that the PGLs were characterised by high dispersions of the maximum standardised uptake value SUVmax (9.7 ± 11, coefficient of variation CV = 114 %), K i (0.0137 ± 0.0119, CV = 87 %), and V (0.292 ± 0.306, CV = 105 %) values. The PGLs were associated with higher PUM (p = 0.02) and T80% (p = 0.02) values and lower k 3 (p = 0.02) values compared to the malignant lesions despite the similar SUVmax values (p = 0.55). The estimations of these new kinetic parameters are more accurate than SUVmax or K i for in vivo metabolic assessment of PGLs at the molecular level.

Radiation doses to cohabitants of patients undergoing radioiodine ablation for thyroid cancer: poor compliance with radiation protection guidelines but low radiation exposure.

BACKGROUND: The drive to reduce hospital stay after radioiodine remnant ablation in patients with thyroid cancer may increase the risk of radiation exposure to family members. The aim of this study was to evaluate the key determinants of dose exposure to familial members, with particular reference to the degree of adherence to current radiation safety guidelines. METHODS: All participants prospectively received our standard departmental oral and written safety instructions, with a mandatory 3-day restriction period. The postmicturition radiation levels of treated patients were measured (at 1-m distance) at the time of discharge using a portable radiometer. The radiation exposure of cohabitants was assessed with an optically stimulated luminescence-based personal dosimeter during the 3 days after hospital discharge. A questionnaire was used to assess the adherence of relatives/cohabitants to radiation safety guidelines. RESULTS: A total of 38 patients with thyroid cancer and 48 household members were included. At 48 h post therapy, the patient's median emission at 1-m distance was 13.4 µSv/h. The mean cumulative cohabitant exposure was 102 µSv (<50-1000). A positive correlation between cohabitant radiation exposure and the radiation level of the patient was observed (P=0.016). This correlation was absent when the recommended guidelines were followed (P=0.56). Only 17 household members (35.4%) strictly followed the recommended guidelines, but dose exposures exceeded 0.3 mSv in only four cases, in which a mean of between 5.8 and 9.5 h were spent in close proximity to the patient in the first 3 days, including sleeping with treated patients in half of the cases. CONCLUSION: Despite poor compliance with safety guidelines, a short-stay protocol respects current legislation, and is applicable to most patients treated with 3.7 GBq for radioiodine remnant ablation.