Trans-cranial Magnetic Resonance-guided Focused UltraSound (tcMRgFUS) system integrated with a 1.5T: an SNR study on DQA phantoms

Background: In recent years transcranial Magnetic Resonance-guided Focused Ultrasound Surgery (tcMRgFUS) treatments have been performed only using 3T units. Since following some internal analysis, planning images obtained using a 1.5T MRI’s body RF coil (as usually done with 3T systems) showed generally reasonable quality in terms of anatomy visualization and SNR but thermal images noise was above acceptable standard for treatments, a dedicated 2-channels head coil was developed (InSightec Ltd.) to ensure an adequate signal-to-noise ratio (SNR). Hence, we present the imaging protocol and the technological methods successfully used with the world-first installation of a certified tcMRgFUS sy…

THALAMIC PARCELLATION FOR TARGET IDENTIFICATION INTRANS-CRANIAL MR-GUIDED FOCUSED ULTRASOUND (TCMRGFUS)THALAMOTOMIES: A PRELIMINARY PROBABILISTC TRACTOGRAPHYSTUDY

Characterization of phenolic pellets for ESR dosimetry in photon beam radiotherapy.

We report a study of the dosimetric features of phenolic compounds for applications in radiation therapy dosimetry of clinical photon beams by using ESR spectroscopy. After the optimization of the ESR readout parameters, basic dosimetric properties (such as intra-batch reproducibility, dose-response, sensitivity, linearity, dose rate dependence, tissue-equivalence and signal stability) of laboratory-made phenolic dosimeters in form of pellets were investigated. Furthermore, these dosimeters were tested for measuring the depth dose profile of a 6 MV clinical photon beam. The results reported show that these dosimeters are promising materials for ESR dosimetric applications in radiation thera…

Analysis of signal-to-noise ratio for a 2-channels coil developed to enable transcranial Magnetic Resonance-guided Focused Ultrasound Surgery (tcMRgFUS) with 1.5 T MRI scanners

Thalamic parcellation for target identification in trans-cranial MR-guided Focused UltraSound (tcMRgFUS) thalamotomies: a preliminary probabilistc tractography study

Background: Trans-cranial MR-guided Focused UltraSound (tcMRgFUS) allows a neurofunctional exploration of thalamic nuclei to confirm and optimize the target before inducing a permanent brain lesion. However, the choice of the target is based on stereotactic coordinates that do not take into account the anatomical variability of each single patient. Thus, the optimization of the treatment target is based on the patient's feedback during lower power sonications. The aim of this work is to retrospectively evaluate the possible role of thalamic parcellation for the identification of the intermediate ventral nucleus (VIM) in patients undergoing tcMRgFUS. Materials and Methods: A 1.5T MR scanner …

Misure preliminari su scanner MRI 7T di stabilità nel tempo di Dosimetri gel di tipo Fricke

L’ottimizzazione delle procedure che utilizzano radiazioni ionizzanti in campo medico costituisce un elemento chiave per la sicurezza del paziente e l’esito dei trattamenti radioterapici. In particolare è fondamentale arrecare il minor danno possibile ai tessuti sani circostanti la neoplasia da trattare (Attix, 2004). La misurazione precisa della dose somministrata nei tessuti e la sua mappatura in tre dimensioni sono di fondamentale importanza in termini di riuscita e di pianificazione dei trattamenti radioterapici (Khan, 2009). In questo lavoro sono presentate le misure preliminari effettuate per testare la stabilità temporale di dosimetri gel di tipo Fricke tramite scanner pre-clinico 7T…

FUNCTIONAL CONNECTIVITY OF THE CEREBELLUM INPATHOLOGICAL GAMBLER

Determinazione della componente gamma nella colone termica del reattore TRIGA di Pavia tramite Dosimetri ESR di alanina

Negli ultimi anni il crescente interesse verso la radioterapia a cattura neutronica (internazionalmente nota come Neutron Capture Therapy - NCT) per il trattamento di neoplasie ha stimolato diverse attività di ricerca finalizzate alla caratterizzazione del fascio utilizzato e all'ottimizzazione delle procedure radioterapiche. Tra i vari sistemi dosimetrici trovano largo impiego i rivelatori a stato solido ESR (Risonanza di Spin Elettronico) a base di alanina che presentano diversi vantaggi come la tessuto equivalenza, la linearità della risposta in un ampio intervallo di dose, l'elevata stabilità dei radicali liberi radioindotti, la non distruttività della lettura del dosimetro e il basso c…

Transcranial Magnetic Resonance-guided Focused Ultrasound Surgery (tcMRgFUS) at 1.5T: this is how we do it

Aims and objectives Methods and materials Results Conclusion Personal information References

Calcolo dei livelli di dose gamma e dei livelli di radon dovuta ai materiali da costruzione

La radioattività delle famiglie di radionuclidi naturali contenuti nei materiali da costruzione è responsabile in una certa misura dell'equivalente di dose riferibile al fondo naturale delle radiazioni. Tale radioattività contribuisce a due fattori di dose: la dose gamma esterna e la dose alfa interna legata all'introduzione e all'accumulo del radon nonché ad un contributo dovuto all’inalazione di polveri nelle quali le concentrazioni dei capostipiti naturali sono alte. I materiali da costruzione sono la sorgente principale del rateo di dose gamma nelle abitazioni. Tutti gli edifici in pietra contengono nuclei radioattivi come 226Ra, 232Th e 40K. É noto che i livelli di radon sono legati al…

Dating of Brazilian shells through electron paramagnetic resonance

In the present work we report dating procedure of these shells by using the electron paramagnetic resonance. The first step of the analysis was the definition of the optimal procedure for sample preparation. At this aim the analysis of the sample composition was carried out by X-ray fluorescence (XRF) measurements and an accurate analysis was study on the effect of the chemical etching with varying typology and concentration of acid to be used for removing the external layer of shells which are affected by alpha particles.

Analisi dei vetri di orologi tramite risonanza paramagnetica elettronica (EPR) e termoluminescenza (TL) per dosimetria retrospettiva

Negli ultimi anni è cresciuto il rischio di esposizioni radiologiche non controllate della popolazione, sia a causa di incidenti associati ad applicazioni industriali e mediche delle radiazioni ionizzanti sia in seguito ad incidenti legati all’abbandono o alla dismissione di sorgenti ma anche ad un uso criminale di materiale radioattivo [1–3]. Gli effetti biologici prodotti dalle radiazioni ionizzanti dipendono fortemente dalla quantità di energia impartita per unità di massa (dose assorbita) [4]. Pertanto, nell’ambito di un incidente radiologico, disporre di procedure di ricostruzione della dose assorbita da un individuo può contribuire oltre che ad identificare i membri della popolazione …

NEW FRICKE GEL WITH HIGH SENSITIVITY AND LOW DIFFUSION FOR3D-MRI DOSIMETRY

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 oxidati…

Resting state functional magnetic resonance imaging analysis of the brain of pathological gamblers

Purpose . Gambling disorder has been recently reclassified under the category ‘‘substance-related and addictive disorders”. Recent studies performed through functional MRI (fMRI) have shown that the perseverance of some behaviors can alter brain activation [1,2]. In this work we aim at investigating functional connectivity changes in pathological gamblers (PGs) in comparison to healthy controls (HCs) by means of resting state functional Magnetic Resonance Imaging (rs-fMRI). Methods and materials. Thirteen HCs and fourteen PGs were recruited (all right handed males; drugs free; mean age 36 ± 10 yrs). All acquisitions were performed through a 1,5 T MRI scanner using a 8-channels phased-array …

Uso della spettroscopia ESR per la caratterizzazione di composti fenolici irradiati con fasci clinici di fotoni ed elettroni

In the last decades several research laboratories have shown an increasing interest aimed at extending the applicability of Electron Spin Resonance (ESR) dosimetry to radiotherapy with different types of radiation beams. ESR is a spectroscopic method for investigating the structure and dynamics of such paramagnetic species. Free radicals are known to be produced when a compound is irradiated with ionizing radiations. The concentration of radiation-induced free radicals is proportional to the energy released inside in the medium and this allows for dosimetric measurements through ESR technique which able to quantitatively determine the radical concentration. The use of alanine as a dosimetri…