Alice Ferretti

Results obtained with a new, very compact detector for imaging with a matrix of leak microstructures (LM) are reported. Spatial linearity and spatial resolution obtained by scanning and the detection of alpha particles with 100% efficiency, when compared with a silicon detector, are stressed. Preliminary results obtained in detecting single electrons emitted by the heated filament (Ec < 1 eV) at 1–3 mbar of propane are reported.

Purpose: Recently new mobile systems for dispensing positron emitters have been produced, designed to guarantee dispensing cycles in an aseptic environment. The aim of the present work was to assess the advantage of one of these systems in radiation protection of operators in clinical settings. Methods: Recently, in our centre the new self-dispensing system named KARL ₁₀₀ by Tema Sinergie was adopted for ¹⁸ F-FDG radiopharmaceuticals. The system is associated with an automatic Rad-inject infuser. The system that was previously used was a fixed isolator NMC DSI (Tema Sinergie), equipped with a μ DDS-An activity fractioning system, together with a pneumatic post for the syringe delivery. The dosimetric evaluations on both systems were carried out through environmental measurements with an ionisation chamber and with the use of personal dosimeters. Results: The operations of preparation and administration of ¹⁸ F-FDG dose to the patient, with the use of Karl ₁₀₀ + RadInject, involve exposures much lower than those obtained by the fixed isolator. The average body exposure of the technician was reduced by 31%, and for the physician by 77%. On the extremities, the equivalent dose to the hands of the technician was reduced by 78%, and for the physician by 96%. Also the additional dosimeters worn by the technician confirmed the estimated environmental assessments. Conclusions: The exposures of the working personnel were significantly reduced with the introduction of the new KARL ₁₀₀ system.

State of the art point-spread function (PSF) corrections implemented in positron emission tomography/computed tomography (PET/CT) reconstruction improved image quality and diagnostic performance but caused an increase in the standardized uptake value (SUV) compared to a conventional OSEM reconstruction system. The EANM suggested one produce two reconstructions, one optimised for maximum lesion detection and one for semi-quantitative analysis. In this work we investigated an alternative methodology, using a single reconstruction data set together with a post-reconstruction algorithm for SUV harmonization. Data acquisition was performed on a Siemens Biograph mCT system equipped with lutetium oxyorthosilicat crystals, PSF and time-of-flight algorithms and on a General Electric Discovery STE system equipped with BGO crystals. Both a EANM double reconstruction method and a dedicated post-reconstruction algorithm (marketed as EQ-filter) were tested to harmonize the quantitative values of the two PET/CT scanners. For phantom measurements we used a NEMA IQ phantom and a Jaszczak cylindrical phantom equipped with small spheres (lesion to background ratios of 8:1 and 4:1). Several different reconstruction settings were tested in order to provide a general methodology. Data obtained by phantom measurements were validated on seven oncologic patients who performed a one-bed extra acquisition on a different scanner. The evaluation regarded 39 small lesions (diameters: 0.3–2.6 cm) and was performed by two experienced nuclear medicine physicians. The SUV recoveries measured with the PSF reconstruction exceeded those obtained by the OSEM reconstruction with deviations ranging from 16% to 150%. These discrepancies resulted below 7% applying the optimized value of the EQ.filter or the double-reconstruction methods. For each reconstruction setting the optimal value of the EQ.filter was identified in order to minimize these discrepancies. Patient data, analyzed by Wilcoxon statistical test, confirmed and validated phantom measurements. EQ.filter can harmonize SUV values between different PET/CT scanners using a single reconstruction optimized to maximum lesion detectability. In this way, the second reconstruction proposed by EANM/EARL is avoided.

Liposomes are lipid vesicles widely used as nanocarriers in targeted drug delivery systems for therapeutic and/or diagnostic purposes. A strategy to prolong the blood circulation time of the liposomes includes the addition of a hydrophilic polymer polyethylene glycol (PEG) moiety onto the surface of the vesicle. Several studies claim that liposome PEGylation by a single chain length or a combination of PEG with different chain lengths may alter the liposomes’ pharmacokinetic properties. Therefore, the purpose of this study was to evaluate the influence of PEG on the biodistribution of pH-sensitive liposomes in a tumor-bearing animal model. Three liposomal formulations (PEGylated or not) were prepared and validated to have a similar mean diameter, monodisperse distribution, and neutral zeta potential. The pharmacokinetic properties of each liposome were evaluated in healthy animals, while the biodistribution and scintigraphic images were evaluated in tumor-bearing mice. High tumor-to-muscle ratios were not statistically different between the PEGylated and non-PEGylated liposomes. While PEGylation is a well-established strategy for increasing the blood circulation of nanostructures, in our study, the use of polymer coating did not result in a better in vivo profile. Further studies must be carried out to confirm the feasibility of the non-PEGylated pH-sensitive liposomes for tumor treatment.

Sentinel lymph node biopsy (SNB) in patients with papillary thyroid carcinoma (PTC) and negative for clinically neck lymph node metastatic involvement (N0) has emerged as a promising minimally invasive procedure to detect metastatic nodes.

A 62-year-old man presented with persistent fever, weakness, and retrosternal pain 3 years after aortic valve bioprosthesis (AVR). His white blood cell count was 11,000/μL and C-reactive protein was 13.6 mg/dL. Consecutive blood cultures isolated Staphylococcus epidermidis and capitis. Transesophageal echocardiography demonstrated small aortic valve prosthesis vegetation. 18F-FDG PET/CT revealed prominent AVR activity, SUVmax = 12.2. He was treated with daptomycin, meropenem, and gentamicin for 1 month and followed by daptomycin and carbapenem for 3 months. Follow-up 18F-FDG PET/CT at 6 months demonstrated complete clearing of AVR activity associated with full asymptomatic recovery.

This 16-year-old boy presented with acute retrosternal pain possibly representing acute myocardial infarction. Cardiac enzymes were within reference ranges. There were marked increases in metanephrine to 3299 μg/24 h (reference, <400 μg/24 h), normetanephrine to 1309 μg/24 h (reference, 0–390 μg/24 h), and chromogranin A to 1605 ng/mL (reference, 0–150 μg/24 h). An incidental left adrenal mass was found during CTPA performed to exclude pulmonary embolism. 123I-MIBG scintigraphy was negative, and genetic screening detected SDHB (succinate dehydrogenase syndrome subunit B) gene mutation. Based on the gene mutation, 18F-DOPA PET/CT was performed, confirming a left-sided pheochromocytoma.