A Medicina Nuclear no Sistema Único de Saúde / Nuclear Medicine in Brazilian Health System

A Medicina Nuclear é crucial para o cuidado de pacientes com doenças, especialmente oncológicas e cardiovasculares. No entanto, o acesso a elaé desigual, devido à falta de equipamentos e unidades produtoras e fornecedoras de insumos. As legislações atuais não abordam adequadamente esses aspectos, e o domínio do capital externo é uma preocupação, pois pode levar ao sucateamento do parque atual. A produção nacional de radiofármacos tem sofrido inúmeros reveses, como cortes orçamentários, a abertura indiscriminada de mercado e o atraso na conclusão doprojeto do Reator Multipropósito Brasileiro. Foram analisados dados públicos de 2015 a 2021 para avaliar o acesso à Medicina Nuclear pelo SUS, incluindo o número de instalações, procedimentos, tarifas e balança comercial.Embora o Brasil tenha muitas instalações de Medicina Nuclear, sua distribuição geográfica é extremamente desigual. Fatores como custosde aquisiçãoemanutençãode equipamentose falta de pessoal qualificado são obstáculos reais à expansão da MN no Brasil. Opaís é financeiramente dependente de capital estrangeiro para essa área, o que limita a expansão da áreade acordo com as diretrizes do SUS. Políticas sociais e econômicas são necessárias para minimizar as vulnerabilidades tecnológicas do SUS, promover a sustentabilidade do sistema e garantir o acesso universal e equânimeaos serviços especializados de saúde.

Protocols for Harmonized Quantification and Noise Reduction in Low-Dose Oncologic 18F-FDG PET/CT Imaging.

Oncologic 18F-FDG PET/CT acquisition and reconstruction protocols need to be optimized for both quantitative and detection tasks. To date, most studies have focused on either quantification or noise, leading to quantitative harmonization guidelines or appropriate noise levels. We developed and evaluated protocols that provide harmonized quantitation with optimal amounts of noise as a function of acquisition parameters and body mass. Methods: Multiple image acquisitions (n = 17) of the International Electrotechnical Commission/National Electrical Manufacturers Association PET image-quality phantom were performed with variable counting statistics. Phantom images were reconstructed with 3-dimensional ordered-subset expectation maximization (OSEM3D) and point-spread function (PSF) for harmonized quantification of the contrast recovery coefficient of the maximum pixel value (CRC max ). The lowest counting statistics that resulted in compliance with European Association of Nuclear Medicine recommendations for CRC max and CRC max variability were used as optimization metrics. Image noise in the liver of 48 typical oncologic 18F-FDG PET/CT studies was analyzed with OSEM3D and PSF harmonized reconstructions. We also evaluated 164 additional 18F-FDG PET/CT reconstructed list-mode images to derive analytic expressions that predict image quality and noise variability. Phantom-to-subject translational analysis was used to derive optimized acquisition and reconstruction protocols. Results: For harmonized quantitation levels, PSF reconstructions yielded decreased noise and lower CRC max variability than regular OSEM3D reconstructions, suggesting they could enable a decreased activity regimen for matched performance. Conclusion: PSF reconstruction with a 7-mm postprocessing filter can provide harmonized quantification performance and acceptable image noise levels with injected activity, duration, and mass settings using a 260 MBq⋅s/kg acquisition parameter at scan time. Similarly, OSEM3D with a 5-mm postprocessing filter can provide similar performance with 401 MBq⋅s/kg.

Calibration of the 90Sr+90Y ophthalmic and dermatological applicators with an extrapolation ionization minichamber.

(90)Sr+(90)Y clinical applicators are used for brachytherapy in Brazilian clinics even though they are not manufactured anymore. Such sources must be calibrated periodically, and one of the calibration methods in use is ionometry with extrapolation ionization chambers. (90)Sr+(90)Y clinical applicators were calibrated using an extrapolation minichamber developed at the Calibration Laboratory at IPEN. The obtained results agree satisfactorily with the data provided in calibration certificates of the sources.

Comparison of the activity measurements in nuclear medicine services in the Brazilian northeast region.

The Northeastern Regional Centre for Nuclear Sciences (CRCN-NE), National Nuclear Energy Commission, has organized for the first time in nuclear medicine services (NMSs) in the Brazilian northeast region a comparison of activity measurements for (99m)Tc, (131)I, (67)Ga, (201)Tl and (57)Co. This tool is widely utilized to evaluate not only the accuracy of radionuclide calibrators, but also the competence of NMSs to measure the activity of the radiopharmaceuticals and the performance of the personnel involved in these measurements. The comparison results showed that 90% of the results received from participants are within the ±10% limit established by the Brazilian Norm.

Radiolysis of 2-[¹8F]fluoro-2-deoxy-D-glucose ([¹8F]FDG) and the role of ethanol, radioactive concentration and temperature of storage.

The 2-[(18)F]-fluoro-2-deoxy-d-glucose ([(18)F]FDG) undergoes radiolysis under high temperature and concentration of activity in the absence of stabilizers. No studies on the influence of transport temperature and concentrations of ethanol, used as stabilizer, higher than 0.1% in the radiolytic stability of [(18)F]FDG are reported. In the present work, [(18)F]FDG samples with activity concentrations between 20 and 130 mCi/mL and with concentrations of 0.1-0.4% ethanol remained stable over 16 h, regardless of storage temperature (5, 25 or 40°C).

Thin CaSO4:Dy thermoluminescent dosimeters for calibration of 90Sr+90Y applicators.

Clinical applicators are used in brachytherapy to treat superficial lesions of skin and eye. They should be periodically calibrated according to quality control programs and international recommendations. Thin CaSO(4):Dy thermoluminescent dosimeters were used to calibrate various applicators with a dermatological applicator as a reference. The obtained absorbed dose rates were compared with those quoted in their calibration certificates. Depth-dose curves were constructed for all the applicators. A mail dosimetry system was developed for calibration of clinical applicators.

TL tandem systems for the determination of effective energy in X radiation beams.

Tandem systems usually comprise two detectors with different radiation energy responses and are utilized to determine the effective energy of unknown radiation beams. The aim of this paper was to evaluate the influence of absorbed dose on tandem curves obtained for different TL materials. In the studied dose interval, the results demonstrate that there is no significant influence of dose on the tandem curves. Therefore, the reliability of these systems for the determination of radiation beam effective energy was confirmed.

A special mini-extrapolation chamber for calibration of 90Sr+90Y sources.

90Sr+90Y applicators are commonly utilized in brachytherapy, including ophthalmic procedures. The recommended instruments for the calibration of these applicators are extrapolation chambers, which are ionization chambers that allow the variation of their sensitive volume. Using the extrapolation method, the absorbed dose rate at the applicator surface can be determined. The aim of the present work was to develop a mini-extrapolation chamber for the calibration of 90Sr+90Y beta ray applicators. The developed mini-chamber has a 3.0 cm outer diameter and is 11.3 cm in length. An aluminized polyester foil is used as the entrance window while the collecting electrode is made of graphited polymethylmethacrylate. This mini-chamber was tested in 90Sr+90Y radiation beams from a beta particle check source and with a plane ophthalmic applicator, showing adequate results.

Performance of different thermoluminescence dosimeters in 90SR+90Y radiation fields.

The dosimetry of beta radiation is a difficult process especially because of the low penetration of beta particles in matter. The dosemeter utilised for this kind of procedure needs to approximate an ideal point-like detector: it should be as thin as possible, and its area should be small. The thermoluminescence dosemeters (TLDs) meet with these requirement properties. The aim of this work was to study the dosimetric characteristics of different TLDs to verify the possibility of their use for the calibration of 90Sr+90Y plane applicators. The response reproducibility, calibration curves, TL response as a function of the source-detector distance, the transmission factors and the linearity of the sample response were obtained for several types of dosimetric pellets.

Thin sintered Al2O3 pellets as thermoluminescent dosimeters for the therapeutic dose range.

Thermoluminescent properties of sintered alumina pellets were investigated with the aim of using them as radiation dosimeters. Peak temperatures, signal reproducibility, fading, curves of the response to X-radiation, as well as energy and angular dependences were studied. The results show that the pellets can be used in quality control programs in the therapeutic dose range.

Properties of sintered amethyst pellets as thermoluminescent dosimeters.

The main dosimetric characteristics of amethyst, Brazilian natural semi-precious stone, were investigated in this work, in order to verify the possibility of its use for gamma-radiation detection using the thermoluminescent (TL) technique. The samples were tested in X- and gamma-radiation beams, and their TL glow curves, dependences of the response on the absorbed dose and radiation energy, and the response reproducibility were investigated. The preliminary results show the usefulness of this material in dosimetry for radiation processing.