Sviluppo di un software per l’analisi di immagini di Diffusion Kurtosis Imaging

L’analisi mediante RM del tensore di diffusione (Diffusion Tensor Imaging, DTI) consente di valutare anche in vivo e con modalità non invasive il processo di diffusione delle molecole d’acqua nei tessuti biologici. La peculiare organizzazione di alcuni tessuti biologici (es: muscoli, sostanza bianca del sistema nervoso centrale e tessuti ad alta cellularità) influenza tale fenomeno rendendolo anisotropo e quindi ben valutabile con tali tecniche di studio. Nonostante i grandi vantaggi di tale tecnica, il DTI è basato su un modello molto semplificato che assume che lo spostamento per diffusione segua un profilo gaussiano il che è molto raro in un ambiente variegato come i tessuti biologici. Per caratterizzare la natura non gaussiana della diffusione dell’acqua nei tessuti è stata sviluppata negli ultimi anni la Diffusion Kurtosis Imaging (DKI) che permette di ottenere ulteriori e più accurate informazioni sulle caratteristiche ultrastrutturali tissutali. Nel presente lavoro si è posto come obiettivo lo sviluppo di un software in grado di ricostruire le mappe tipiche della DKI. In particolare, il software è stato sviluppato in linguaggio di programmazione “Python” e permette di estrarre i parametri DTI e DKI da una serie di dati acquisiti per vari valori di b e per un vario numero di direzioni di gradienti

Improvement of neutron sensitivity for lithium formate ESR dosimeters: A Monte Carlo analysis

This work presents the computational analysis of the sensitivity improvements that could be achieved in lithium formate monohydrate (LFM) electron paramagnetic resonance (EPR) dosemeters exposed to neutron beams. Monte Carlo (MC) simulations were performed on LFM pellets exposed to neutron beams with different energy spectra at various depths inside a water phantom. Various computations were carried out by considering different enrichments of 6Li inside the LFM matrix as well as addition of different amounts of gadolinium oxide inside the pellet blend. The energy released per unit mass was calculated with the aim of redicting the increase in dose achievable by the addition of sensitizers inside the pellets. As expected, a larger amount of 6Li induces an increase of energy released because of the charged secondary particles (i.e. 3H ions and α particles) produced after neutron capture. For small depths in water phantom and low-energy neutron spectra the dose increase due to 6Li enrichment is high (more than three orders of magnitude with respect to the case of with 7Li). In case of epithermal neutron beams the energy released in 6Li-enriched LFM compound is smaller but larger than in the case of fast neutron beams. On the other hand, the computational analysis evidenced that gadolinium is less effective than 6Li in improving neutron sensitivity of the LFM pellets. Discussion based on the features of MC transport code is provided. This result suggests that 6Li enrichment of LFM dosemeters would be more effective for neutron sensitivity improvement and these EPR dosemeters could be tested for dosimetric applications in Neutron Capture Therapy

Does exergaming promote neurofunctional changes in Parkinson ́s disease? A pilot clinical study

ntrodução: Estudos anteriores demonstraram efeitos bené- ficos em pessoas com doença de Parkinson treinadas com exergames. No entanto, até onde sabe-se, nenhum deles avaliou se esses efeitos são sustentados por alterações neurofuncionais. Objetivo: Avaliar os efeitos neurofuncionais de um treinamento, por meio da ressonância magnética funcional, em pessoas com doença de Parkinson. Métodos: Trata-se de um ensaio clínico piloto cego, randomizado e controlado com delineamento crossover. Os participantes foram submetidos a uma avaliação incluindo desempenho cognitivo e ressonância magnética funcional antes e após treinamentos com Wii® ou controle. Os treinamentos foram aplicados durante 10 dias, em duas semanas consecutivas. Os participantes que começaram o treinamento com Wii® foram depois movidos para o treinamento de controle e vice-versa. Respeitou-se um período de wash-out de 45 dias entre os treinamentos. Resultados: Memória, funções execu- tivas e visuoespaciais e atenção melhoraram significativamente em comparação com a linha de base (p < 0,05). Não foram observadas diferenças na cognição em comparação com o treinamento de controle. Embora não significativos, os resultados das análises de ressonância magnética funcional sugeriram que o treinamento com Wii® poderia promover melhorias na conectividade funcional do cérebro, especialmente em áreas envolvidas na execução motora, planejamento, funções visuais, de memória e somatossensoriais. Conclusão: Em pessoas com doença de Parkinson, um treinamento intensivo com Wii® melhorou o desempenho cognitivo, que destacou mudanças neurofuncionais em áreas envolvidas no processamento cognitivo.Introduction: Previous studies have demonstrated beneficial effects in people with Parkinson ́s disease trained with exergames. However, to the best of our knowledge, none of them evaluated whether these effects are sustained by neurofunctional changes. Objective: To evaluate neurofunctional effects of a training, by means of functional magnetic resonance imaging, in people with Parkinson ́s disease. Methods: This study was a blind, randomized, and controlled pilot clinical trial with crossover design. The participants were submitted to an evaluation including cognitive performance and functional magnetic resonance imaging before and after the WiiTM or control trainings. Trainings were applied for 10 days, in two consecutive weeks. Participants starting with WiiTM training were then moved to the control training and vice versa. A wash-out period of 45 days between the trainings was respected. Results: Memory, executive and visuo-spatial functions, and attention were significantly improved compared to baseline (p < 0.05). No differences were observed in cognition compared to the control training. Though not significant, results of functional magnetic resonance imaging analyses suggested that WiiTM training could promote improvements on the brain functional connectivity especially in areas involved in motor execution, planning, visual, memory and somatosensory functions. Conclusion: In people with Parkinson ́s disease, an intensive WiiTM training improved cognitive performance that underlined neurofunctional changes in areas involved in cognitive processing

Modulation of Human Motor Cortical Excitability and Plasticity by Opuntia Ficus Indica Fruit Consumption: Evidence from a Preliminary Study through Non-Invasive Brain Stimulation

Indicaxanthin (IX) from Opuntia Ficus Indica (OFI) has been shown to exert numerous biological effects both in vitro and in vivo, such as antioxidant, anti-inflammatory, neuro-modulatory activity in rodent models. Our goal was to investigate the eventual neuro-active role of orally assumed fruits containing high levels of IX at nutritionally-relevant amounts in healthy subjects, exploring cortical excitability and plasticity in the human motor cortex (M1). To this purpose, we applied paired-pulse transcranial magnetic stimulation and anodal transcranial direct current stimulation (a-tDCS) in basal conditions and followed the consumption of yellow cactus pear fruits containing IX or white cactus pear fruits devoid of IX (placebo). Furthermore, resting state-functional MRI (rs-fMRI) preliminary acquisitions were performed before and after consumption of the same number of yellow fruits. Our data revealed that the consumption of IX-containing fruits could specifically activate intracortical excitatory circuits, differently from the placebo-controlled group. Furthermore, we found that following the ingestion of IX-containing fruits, elevated network activity of glutamatergic intracortical circuits can homeostatically be restored to baseline levels following a-tDCS stimulation. No significant differences were observed through rs-fMRI acquisitions. These outcomes suggest that IX from OFI increases intracortical excitability of M1 and leads to homeostatic cortical plasticity responses

PERFORMANCE OF DIFFUSION KURTOSIS IMAGING FOR CHARACTERIZATION OF PROSTATE LESIONS USING 1.5T MAGNETIC RESONANCE IMAGING SCANNER

The aim of the study is to evaluate the diagnostic performance of apparent diffusion coefficient (ADC) and apparent kurtosis coefficient (Kapp) for the characterization of prostate lesions on 1.5T MRI. This retrospective study included 34 patients with at least one lesion with PI-RADS score≥ 3. Performances of ADC and Kapp were evaluated using the Mann-Whitney U test and receiver operating characteristics curve (AUROC). Lesions with Gleason score≥6 had significantly lower Kapp compared to benign lesions (p=0.025). The ADC-ratio was the only significantly different parameter between GS≥7 and GS=6 lesions (p=0.039). Kapp showed the largest AUROC for the diagnosis of GS≥6 prostate cancers (AUROC: 0.741, p=0.025), while the largest AUROC for the diagnosis of GS≥7 prostate cancers was achieved by the ADC-ratio (AUROC: 0.709, p=0.039). While Kapp demonstrated no significant benefit in characterization of prostate cancers compared to ADC, it could be helpful to distinguish benign lesions from prostate cancers

Preoperative imaging findings in patients undergoing transcranial magnetic resonance imaging-guided focused ultrasound thalamotomy

The prevalence and impact of imaging findings detected during screening procedures in patients undergoing transcranial MR-guided Focused Ultrasound (tcMRgFUS) thalamotomy for functional neurological disorders has not been assessed yet. This study included 90 patients who fully completed clinical and neuroradiological screenings for tcMRgFUS in a single-center. The presence and location of preoperative imaging findings that could impact the treatment were recorded and classified in three different groups according to their relevance for the eligibility and treatment planning. Furthermore, tcMRgFUS treatments were reviewed to evaluate the number of transducer elements turned off after marking as no pass regions the depicted imaging finding. A total of 146 preoperative imaging findings in 79 (87.8%) patients were detected in the screening population, with a significant correlation with patients' age (rho = 483, p < 0.001). With regard of the group classification, 119 (81.5%), 26 (17.8%) were classified as group 1 or 2, respectively. One patient had group 3 finding and was considered ineligible. No complications related to the preoperative imaging findings occurred in treated patients. Preoperative neuroradiological findings are frequent in candidates to tcMRgFUS and their identification may require the placement of additional no-pass regions to prevent harmful non-targeted heating

PVA-GTA Fricke gel dosimeters exposed to clinical photons beams: Nuclear Magnetic Resonance Relaxometry and Imaging

Fricke Gel (FXGs) dosimetric system is based on the radiation induced oxidation of ferrous to ferric ions. The application of Fricke gels for ionizing radiation dosimetry is continuously increasing worldwide due to their many favorable properties. However, one of their shortcomings is that ferrous and ferric ions diffuse in the gel matrix. To maintain the spatial integrity of the dose distribution, Fricke gels must be undergoing measurement within a few hours of their irradiation, so that ferric ions remain close to their point of production. Thus, the spatial integrity of the dose distribution in the Fricke gel is maintained (Schreiner, 2015). The gel matrix also contributes to the oxidation of ferrous ions during irradiation, increasing the chemical yield of ferric ions in aqueous solution and increasing the sensitivity of the dosimeter. The oxidation of ferrous ions also causes a reduction of the longitudinal nuclear magnetic relaxation time T1 which can be measured by means of Nuclear Magnetic Resonance Relaxometry (NMR) and Magnetic Resonance Imaging (MRI) (Marrale, 2014). The results here presented are related to an experimental investigation conducted on Fricke Gels characterized by gelatinous matrix of Polyvinyl alcohol (PVA) cross-linked with a Glutaraldehyde (GTA) (Marini, 2016). The main dosimetric features of the NMR signal were investigated. The gels were irradiated in the clinical dose range between 0 and 20 Gy. In order to assess the photon sensitivity we analyzed the dependence of NMR relaxation times on radiation dose with varying ferrous ammonium sulfate content inside FXGs. Furthermore, signal stability was followed for several days after irradiation. These measurements were preliminary to MRI analysis which can permit 3D dose mapping. In order to maximize the MRI response a systematic study was performed to optimize acquisition sequences and parameters. In particular, we analyzed for inversion recovery sequences the dependence of MRI signal on the repetition time TR and on the inversion time TI. The dose calibration curves are reported and discussed from the point of view of the dosimeter use in clinical radiotherapy. This work has highlighted that the optimization of additives inside gel matrix is fundamental for maximizing photon sensitivity of these detectors. We can conclude that FXG dosimeters with optimal ferrous ammonium sulfate content can be regarded as a valuable dosimetric tool to achieve fast information on spatial dose distribution