The identification of gastrointestinal (GI) motility disorders requires the evaluation of regional GI transit, and the development of alternative methodologies in animals has a significant impact on translational approaches. Therefore, the purpose of this study was to validate an easy and low-cost methodology (alternate current biosusceptometry – ACB) for the assessment of regional GI transit in rats through images. Rats were fed a test meal containing magnetic tracer and phenol red, and GI segments (stomach, proximal, medial and distal small intestine, and cecum) were collected to assess tracer’s retention at distinct times after ingestion (0, 60, 120, 240, and 360 min). Images were obtained by scanning the segments, and phenol red concentration was determined by the sample’s absorbance. The temporal retention profile, geometric center, gastric emptying, and cecum arrival were evaluated. The correlation coefficient between methods was 0.802, and the temporal retention of each segment was successfully assessed. GI parameters yielded comparable results between methods, and ACB images presented advantages as the possibility to visualize intrasegmental tracer distribution and the automated scan of the segments. The imaging approach provided a reliable assessment of several parameters simultaneously and may serve as an accurate and sensitive approach for regional GI research in rats.

Neste trabalho foram analisadas as resoluções espaciais de sensores de Biosusceptometria AC (BAC) com diferentes diâmetros de bobinas e distâncias do objeto simulador. Com o uso de ferrita de manganês, como um fantoma pontual, foram adquiridas as Funções de Espalhamento Pontual dos sistemas e, através delas, foram quantificadas as resoluções dos sensores. Para isso, foram utilizados dois métodos consagrados em análise de resolução: a função de transferência modulada e a largura à meia altura. Os resultados demonstraram que para todos os diâmetros a menor distância apresentou melhores resoluções, enquanto para ambas distâncias o menor diâmetro apresentou melhores resoluções. Ao correlacionar os dois métodos para todos os casos foram obtidos perfis lineares, portanto, os métodos possuem alta similaredade quando aplicados ao sistema BAC. Com isso, podemos aferir a resolução espacial do sensor, onde foi possível realizar otimizações de geometria do sistema e posicionamentos conforme a medida a ser realizada e possíveis aplicações.

Background Non-invasive magnetic imaging techniques are necessary to assist magnetic nanoparticles in biomedical applications, mainly detecting their distribution inside the body. In Alternating Current Biosusceptometry (ACB), the magnetic nanoparticle's magnetization response under an oscillating magnetic field, which is applied through an excitation coil, is detected with a balanced detection coil system. Results We built a Multi-Channel ACB system (MC-ACB) containing nineteen pick-up coils and obtained 2D quantitative images of magnetic nanoparticle distributions by solving an inverse problem. We reconstructed the magnetic nanoparticles spatial distributions in a field of view of 14 × 14 cm2 with a spatial resolution of 2.0 cm and sensitivity in the milligram scale. A correlation coefficient between quantitative reconstructed and nominal magnetic nanoparticle distributions above 0.6 was found for all measurements. Conclusion Besides other interesting features such as sufficient large field of view dimension for mice and rat studies, portability, and the ability to assess the quantitative magnetic nanoparticles distributions in real-time, the MC-ACB system is a promising tool for quantitative imaging of magnetic nanoparticles distributions in real-time, offering an affordable setup for easy access in clinical or laboratory environments.

The use of magnetic nanoparticles (MNPs) in biomedical applications requires the quantitative knowledge of their quantitative distribution within the body. AC Biosusceptometry (ACB) is a biomagnetic technique recently employed to detect MNPs in vivo by measuring the MNPs response when exposed to an alternate magnetic field. The ACB technique presents some interesting characteristics: non-invasiveness, low operational cost, high portability, and no need for magnetic shielding. ACB conventional methods until now provided only qualitative information about the MNPs’ mapping in small animals. We present a theoretical model and experimentally demonstrate the feasibility of ACB reconstructing 2D quantitative images of MNPs’ distributions. We employed an ACB single-channel scanning approach, measuring at 361 sensor positions, to reconstruct MNPs’ spatial distributions. For this, we established a discrete forward problem and solved the ACB system’s inverse problem. Thus, we were able to determine the positions and quantities of MNPs in a field of view of 5×5×1 cm3 with good precision and accuracy. The results show the ACB system’s capabilities to reconstruct the quantitative spatial distribution of MNPs with a spatial resolution better than 1 cm, and a sensitivity of 1.17 mg of MNPs fixed in gypsum. These results show the system’s potential for biomedical application of MNPs in several studies, for example, electrochemical-functionalized MNPs for cancer cell targeting, quantitative sensing, and possibly in vivo imaging.

Nuclear Medicine employs unsealed radioactive sources, which are further administered to patients. After radiopharmaceutical capture by an organ of interest, the examination is performed. The transportation of radioactive sources within the Nuclear Medicine Department entails different rates of exposure to ionizing radiation. This affects the dosimetry of occupationally exposed individuals and individuals of the public. The National Commission for Nuclear Energy (CNEN) sets dose limits for both groups of individuals in order to protect them from the effects of ionizing radiation. Based on these assumptions, the objective of this study was to assess the rates of exposures in nuclear