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1.
Neurocirugía (Soc. Luso-Esp. Neurocir.) ; 31(4): 158-164, jul.-ago. 2020. ilus, tab
Artigo em Espanhol | IBECS | ID: ibc-193896

RESUMO

INTRODUCCIÓN: Los tumores neuroepiteliales disembrioplásicos (DNET) son un tipo de neoplasia glioneuronal benigna de localización típicamente temporal que producen crisis epilépticas resistentes al tratamiento farmacológico en niños y adultos jóvenes. OBJETIVO: Se muestran 4 casos valorando la utilidad de la resonancia magnética funcional en el estudio prequirúrgico de pacientes con tumores neuroepiteliales disembrionarios. Para la obtención de imágenes se utilizó un equipo de resonancia magnética Philipps Intera de 3.0 Tesla y la técnica Blood Oxygenation Level-Dependent, permitiendo localizar las áreas elocuentes de lenguaje y motora mediante la aplicación de paradigmas específicos. RESULTADOS: En un caso el tumor se encontraba adyacente al área de Broca, en 2 casos coincidía con Wernicke, en un paciente estaba menos de 1cm del área motora de la mano y en otro próximo a la memoria. Solo 2 de los pacientes fueron operados, no produciéndose déficit funcional postoperatorio. Se observó activación hemisférica contralateral al tumor sugestivo de neuroplasticidad en uno de los pacientes. CONCLUSIONES: La resonancia magnética funcional supone un método no invasivo que permite evaluar la proximidad de las lesiones a las áreas elocuentes, clave en la evaluación del riesgo quirúrgico. Además, ha permitido detectar probable neuroplasticidad en un caso, la cual ha garantizado el éxito de la cirugía


INTRODUCTION: Dysembryoplastic neuroepithelial tumours (DNET) are a type of benign glioneuronal neoplasia of typically temporal location that produce drug-resistant epileptic seizures in children and young adults. OBJECTIVE: This work aims to assess the usefulness of functional magnetic resonance imaging (fMRI) in the preoperative study in four patients with DNET. A Philips Intera 3.0 Tesla magnetic resonance imaging scanner and the Blood-Oxygen-Level-Dependent (BOLD) technique were used to obtain the images, making it possible to locate the eloquent areas for language and motor areas through the application of specific paradigms. RESULTS: In one case the tumour was adjacent to Broca's area, in two cases it coincided with Wernicke's area, in one patient it was < 1cm from the motor area for the hand and in another close to memory. Only two of the patients were operated on, without postoperative functional deficit. Hemispheric activation contralateral to the tumour suggestive of neuroplasticity was observed in one of the patients. CONCLUSIONS: fMRI is a non-invasive method that allows us to assess the proximity of lesions to eloquent areas, which is key in the evaluation of surgical risk. In addition, it allowed the detection of probable neuroplasticity in one case, which guaranteed the success of the surgery


Assuntos
Humanos , Neoplasias Neuroepiteliomatosas/diagnóstico por imagem , Neoplasias Neuroepiteliomatosas/fisiopatologia , Encefalopatias/patologia , Lateralidade Funcional/fisiologia , Neuroimagem Funcional/métodos , Imagem por Ressonância Magnética/instrumentação , Área de Wernicke/diagnóstico por imagem , Encefalopatias/fisiopatologia
2.
Neurocirugía (Soc. Luso-Esp. Neurocir.) ; 31(4): 184-194, jul.-ago. 2020. ilus
Artigo em Espanhol | IBECS | ID: ibc-193899

RESUMO

INTRODUCCIÓN: La cirugía de los tumores cerebrales se ha implementado en los últimos años con nuevas técnicas de imagen intraoperatoria, que tratan de mejorar la resección tumoral, aunque conllevan un aumento de recursos. Con el fin de hacer una actualización de este tema, se ha elaborado este manuscrito desde el grupo de tumores de la Sociedad Española de Neurocirugía. MATERIAL Y MÉTODOS: Se ha propuesto a expertos en el uso de cada una de las técnicas intraoperatorias más empleadas en la cirugía de los tumores cerebrales, la descripción de la técnica y una breve revisión de la literatura. Se describirán indicaciones de uso, sus ventajas e inconvenientes basados en la experiencia clínica y en lo publicado en la literatura. RESULTADOS: La técnica de imagen intraoperatoria más consistente sería la resonancia de bajo y alto campo, pero a su vez es la que supone un mayor gasto de recursos. La ecografía intraoperatoria navegada es portátil y tiene un menor coste, aunque discrimina peor los tumores de alto grado y es observador-dependiente. Las técnicas de fluorescencia más empleadas son el 5-aminolevulínico para gliomas de alto grado y la fluoresceína, de utilidad en lesiones que rompen la barrera hematoencefálica. Por último, la TAC intraoperatoria es la más versátil en el quirófano de neurocirugía, pero tiene menos indicaciones en la cirugía neurooncológica. CONCLUSIONES: Las técnicas de imagen intraoperatoria se emplean cada vez con más frecuencia en la cirugía de los tumores cerebrales, y el neurocirujano debe valorar su posible uso en función de sus recursos y las necesidades de cada paciente


INTRODUCTION: New intraoperative imaging techniques, which aim to improve tumour resection, have been implemented in recent years in brain tumour surgery, although they lead to an increase in resources. In order to carry out an update on this topic, this manuscript has been drafted by a group from the Sociedad Española de Neurocirugía (Spanish Society of Neurosurgery). MATERIAL AND METHODS: Experts in the use of each one of the most-used intraoperative techniques in brain tumour surgery were presented with a description of the technique and a brief review of the literature. Indications for use, their advantages and disadvantages based on clinical experience and on what is published in the literature will be described. RESULTS: The most robust intraoperative imaging technique appears to be low- and high-field magnetic resonance imaging, but this is the technique which results in the greatest expenditure. Intraoperative ultrasound navigation is portable and less expensive, but it provides poorer differentiation of high-grade tumours and is observer-dependent. The most-used fluorescence techniques are 5-aminolevulinic acid for high-grade gliomas and fluorescein, useful in lesions which rupture the blood-brain barrier. Last of all, intraoperative CT is more versatile in the neurosurgery operating theatre, but it has fewer indications in neuro-oncology surgery. CONCLUSIONS: Intraoperative imaging techniques are used with increasingly greater frequency in brain tumour surgery, and the neurosurgeon should assess their possible use depending on their resources and the needs of each patient


Assuntos
Humanos , Neoplasias Encefálicas/cirurgia , Procedimentos Neurocirúrgicos , Processamento de Imagem Assistida por Computador , Monitorização Intraoperatória/instrumentação , Imagem por Ressonância Magnética/instrumentação , Monitorização Intraoperatória/normas , Imagem por Ressonância Magnética/normas
3.
Nat Commun ; 11(1): 3840, 2020 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-32737293

RESUMO

Currently, human magnetic resonance (MR) examinations are becoming highly specialized with a pre-defined and often relatively small target in the body. Conventionally, clinical MR equipment is designed to be universal that compromises its efficiency for small targets. Here, we present a concept for targeted clinical magnetic resonance imaging (MRI), which can be directly integrated into the existing clinical MR systems, and demonstrate its feasibility for breast imaging. The concept comprises spatial redistribution and passive focusing of the radiofrequency magnetic flux with the aid of an artificial resonator to maximize the efficiency of a conventional MR system for the area of interest. The approach offers the prospect of a targeted MRI and brings novel opportunities for high quality specialized MR examinations within any existing MR system.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Cerâmica/efeitos da radiação , Espectroscopia Dielétrica/métodos , Imagem por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Adulto , Cerâmica/química , Espectroscopia Dielétrica/instrumentação , Radiação Eletromagnética , Desenho de Equipamento , Feminino , Voluntários Saudáveis , Humanos , Imagem por Ressonância Magnética/instrumentação , Imagens de Fantasmas , Razão Sinal-Ruído
4.
PLoS One ; 15(8): e0238112, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32857805

RESUMO

This longitudinal study was performed to evaluate the feasibility of detecting the interaction between wall shear stress (WSS) and plaque development. 20 ApoE-/- mice were separated in 12 mice with Western Diet and 8 mice with Chow Diet. Magnetic resonance (MR) scans at 17.6 Tesla and histological analysis were performed after one week, eight and twelve weeks. All in vivo MR measurements were acquired using a flow sensitive phase contrast method for determining vectorial flow. Histological sections were stained with Hematoxylin and Eosin, Elastica van Gieson and CD68 staining. Data analysis was performed using Ensight and a Matlab-based "Flow Tool". The body weight of ApoE-/- mice increased significantly over 12 weeks. WSS values increased in the Western Diet group over the time period; in contrast, in the Chow Diet group the values decreased from the first to the second measurement point. Western Diet mice showed small plaque formations with elastin fragmentations after 8 weeks and big plaque formations after 12 weeks; Chow Diet mice showed a few elastin fragmentations after 8 weeks and small plaque formations after 12 weeks. Favored by high-fat diet, plaque formation results in higher values of WSS. With wall shear stress being a known predictor for atherosclerotic plaque development, ultra highfield MRI can serve as a tool for studying the causes and beginnings of atherosclerosis.


Assuntos
Aorta/diagnóstico por imagem , Imagem por Ressonância Magnética , Placa Aterosclerótica/diagnóstico por imagem , Animais , Aorta/patologia , Aorta/fisiopatologia , Apolipoproteínas E/deficiência , Apolipoproteínas E/genética , Aterosclerose/diagnóstico por imagem , Aterosclerose/patologia , Aterosclerose/fisiopatologia , Peso Corporal , Dieta Ocidental , Modelos Animais de Doenças , Estudos de Viabilidade , Feminino , Estudos Longitudinais , Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Camundongos Knockout , Placa Aterosclerótica/patologia , Placa Aterosclerótica/fisiopatologia , Distribuição Aleatória , Fluxo Sanguíneo Regional , Estresse Mecânico
5.
PLoS One ; 15(8): e0237494, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32804972

RESUMO

Modern magnetic resonance imaging systems are equipped with a large number of receive connectors in order to optimally support a large field-of-view and/or high acceleration in parallel imaging using high-channel count, phased array coils. Given that the MR system is equipped with a limited number of digitizing receivers and in order to support operation of multinuclear coil arrays, these connectors need to be flexibly routed to the receiver outside the RF shielded examination room. However, for a number of practical, economic and safety reasons, it is better to only route a subset of the connectors. This is usually accomplished with the use of switch matrices. These exist in a variety of topologies and differ in routing flexibility and technological implementation. A highly flexible implementation is a crossbar topology that allows to any one input to be routed to any one output and can use single PIN diodes as active elements. However, in this configuration, long open-ended transmission lines can potentially remain connected to the signal path leading to high transmission losses. Thus, especially for high-field systems compensation mechanisms are required to remove the effects of open-ended transmission line stubs. The selection of a limited number of lumped element reactance values to compensate for the for the effect of transmission line stubs in large-scale switch matrices capable of supporting multi-nuclear operation is non-trivial and is a combinatorial problem of high order. Here, we demonstrate the use of metaheuristic approaches to optimize the circuit design of these matrices that additionally carry out the optimization of distances between the parallel transmission lines. For a matrix with 128 inputs and 64 outputs a realization is proposed that displays a worst-case insertion loss of 3.8 dB.


Assuntos
Imagem por Ressonância Magnética/métodos , Algoritmos , Desenho de Equipamento , Imagem por Ressonância Magnética/instrumentação , Processamento de Sinais Assistido por Computador , Razão Sinal-Ruído
6.
Medicine (Baltimore) ; 99(28): e21125, 2020 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-32664139

RESUMO

OBJECTIVE: The aim of this study was to characterize the capability of detection of the resting state networks (RSNs) with functional magnetic resonance imaging (fMRI) in healthy subjects using a 1.5T scanner in a middle-income country. MATERIALS AND METHODS: Ten subjects underwent a complete blood-oxygen-level dependent imaging (BOLD) acquisition on a 1.5T scanner. For the imaging analysis, we used the spatial independent component analysis (sICA). We designed a computer tool for 1.5 T (or above) scanners for imaging processing. We used it to separate and delineate the different components of the RSNs of the BOLD signal. The sICA was also used to differentiate the RSNs from noise artifact generated by breathing and cardiac cycles. RESULTS: For each subject, 20 independent components (IC) were computed from the sICA (a total of 200 ICs). From these ICs, a spatial pattern consistent with RSNs was identified in 161 (80.5%). From the 161, 131 (65.5%) were fit for study. The networks that were found in all subjects were: the default mode network, the right executive control network, the medial visual network, and the cerebellar network. In 90% of the subjects, the left executive control network and the sensory/motor network were observed. The occipital visual network was present in 80% of the subjects. In 39 (19.5%) of the images, no any neural network was identified. CONCLUSIONS: Reproduction and differentiation of the most representative RSNs was achieved using a 1.5T scanner acquisitions and sICA processing of BOLD imaging in healthy subjects.


Assuntos
Encéfalo/diagnóstico por imagem , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética/instrumentação , Rede Nervosa/diagnóstico por imagem , Descanso/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Mapeamento Encefálico/métodos , Desenho de Equipamento , Feminino , Seguimentos , Voluntários Saudáveis , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Estudos Retrospectivos
7.
PLoS One ; 15(7): e0236295, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32706813

RESUMO

The purpose of the present study was to integrate an interactive gradient-based needle navigation system and to evaluate the feasibility and accuracy of the system for real-time MR guided needle puncture in a multi-ring phantom and in vivo in a porcine model. The gradient-based navigation system was implemented in a 1.5T MRI. An interactive multi-slice real-time sequence was modified to provide the excitation gradients used by two sets of three orthogonal pick-up coils integrated into a needle holder. Position and orientation of the needle holder were determined and the trajectory was superimposed on pre-acquired MR images. A gel phantom with embedded ring targets was used to evaluate accuracy using 3D distance from needle tip to target. Six punctures were performed in animals to evaluate feasibility, time, overall error (target to needle tip) and system error (needle tip to the guidance needle trajectory) in vivo. In the phantom experiments, the overall error was 6.2±2.9 mm (mean±SD) and 4.4±1.3 mm, respectively. In the porcine model, the setup time ranged from 176 to 204 seconds, the average needle insertion time was 96.3±40.5 seconds (min: 42 seconds; max: 154 seconds). The overall error and the system error was 8.8±7.8 mm (min: 0.8 mm; max: 20.0 mm) and 3.3±1.4 mm (min: 1.8 mm; max: 5.2 mm), respectively.


Assuntos
Biópsia por Agulha , Biópsia Guiada por Imagem , Imagem por Ressonância Magnética , Punções , Animais , Biópsia por Agulha/instrumentação , Biópsia por Agulha/métodos , Biópsia Guiada por Imagem/instrumentação , Biópsia Guiada por Imagem/métodos , Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Agulhas , Imagens de Fantasmas , Punções/instrumentação , Punções/métodos , Suínos
8.
Br J Radiol ; 93(1111): 20200113, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32496816

RESUMO

MRI developed during the last half-century from a very basic concept to an indispensable non-ionising medical imaging technique that has found broad application in diagnostics, therapy control and far beyond. Due to its excellent soft-tissue contrast and the huge variety of accessible tissue- and physiological-parameters, MRI is often preferred to other existing modalities. In the course of its development, MRI underwent many substantial transformations. From the beginning, starting as a proof of concept, much effort was expended to develop the appropriate basic scanning technology and methodology, and to establish the many clinical contrasts (e.g., T1, T2, flow, diffusion, water/fat, etc.) that MRI is famous for today. Beyond that, additional prominent innovations to the field have been parallel imaging and compressed sensing, leading to significant scanning time reductions, and the move towards higher static magnetic field strengths, which led to increased sensitivity and improved image quality. Improvements in workflow and the use of artificial intelligence are among many current trends seen in this field, paving the way for a broad use of MRI. The 125th anniversary of the BJR is a good point to reflect on all these changes and developments and to offer some slightly speculative ideas as to what the future may bring.


Assuntos
Invenções/tendências , Imagem por Ressonância Magnética/tendências , Inteligência Artificial/tendências , Meios de Contraste , Aprendizado Profundo/tendências , Humanos , Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Magnetismo , Fluxo de Trabalho
9.
Nat Commun ; 11(1): 3032, 2020 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-32541769

RESUMO

Tumor heterogeneity is one major reason for unpredictable therapeutic outcomes, while stratifying therapeutic responses at an early time may greatly benefit the better control of cancer. Here, we developed a hybrid nanovesicle to stratify radiotherapy response by activatable inflammation magnetic resonance imaging (aiMRI) approach. The high Pearson's correlation coefficient R values are obtained from the correlations between the T1 relaxation time changes at 24-48 h and the ensuing adaptive immunity (R = 0.9831) at day 5 and the tumor inhibition ratios (R = 0.9308) at day 18 after different treatments, respectively. These results underscore the role of acute inflammatory oxidative response in bridging the innate and adaptive immunity in tumor radiotherapy. Furthermore, the aiMRI approach provides a non-invasive imaging strategy for early prediction of the therapeutic outcomes in cancer radiotherapy, which may contribute to the future of precision medicine in terms of prognostic stratification and therapeutic planning.


Assuntos
Imagem por Ressonância Magnética/métodos , Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Imunidade Adaptativa , Animais , Humanos , Imagem por Ressonância Magnética/instrumentação , Camundongos , Neoplasias/imunologia , Espécies Reativas de Oxigênio/imunologia
10.
J Cardiovasc Magn Reson ; 22(1): 31, 2020 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-32375896

RESUMO

BACKGROUND: The T1 Mapping and Extracellular volume (ECV) Standardization (T1MES) program explored T1 mapping quality assurance using a purpose-developed phantom with Food and Drug Administration (FDA) and Conformité Européenne (CE) regulatory clearance. We report T1 measurement repeatability across centers describing sequence, magnet, and vendor performance. METHODS: Phantoms batch-manufactured in August 2015 underwent 2 years of structural imaging, B0 and B1, and "reference" slow T1 testing. Temperature dependency was evaluated by the United States National Institute of Standards and Technology and by the German Physikalisch-Technische Bundesanstalt. Center-specific T1 mapping repeatability (maximum one scan per week to minimum one per quarter year) was assessed over mean 358 (maximum 1161) days on 34 1.5 T and 22 3 T magnets using multiple T1 mapping sequences. Image and temperature data were analyzed semi-automatically. Repeatability of serial T1 was evaluated in terms of coefficient of variation (CoV), and linear mixed models were constructed to study the interplay of some of the known sources of T1 variation. RESULTS: Over 2 years, phantom gel integrity remained intact (no rips/tears), B0 and B1 homogenous, and "reference" T1 stable compared to baseline (% change at 1.5 T, 1.95 ± 1.39%; 3 T, 2.22 ± 1.44%). Per degrees Celsius, 1.5 T, T1 (MOLLI 5s(3s)3s) increased by 11.4 ms in long native blood tubes and decreased by 1.2 ms in short post-contrast myocardium tubes. Agreement of estimated T1 times with "reference" T1 was similar across Siemens and Philips CMR systems at both field strengths (adjusted R2 ranges for both field strengths, 0.99-1.00). Over 1 year, many 1.5 T and 3 T sequences/magnets were repeatable with mean CoVs < 1 and 2% respectively. Repeatability was narrower for 1.5 T over 3 T. Within T1MES repeatability for native T1 was narrow for several sequences, for example, at 1.5 T, Siemens MOLLI 5s(3s)3s prototype number 448B (mean CoV = 0.27%) and Philips modified Look-Locker inversion recovery (MOLLI) 3s(3s)5s (CoV 0.54%), and at 3 T, Philips MOLLI 3b(3s)5b (CoV 0.33%) and Siemens shortened MOLLI (ShMOLLI) prototype 780C (CoV 0.69%). After adjusting for temperature and field strength, it was found that the T1 mapping sequence and scanner software version (both P < 0.001 at 1.5 T and 3 T), and to a lesser extent the scanner model (P = 0.011, 1.5 T only), had the greatest influence on T1 across multiple centers. CONCLUSION: The T1MES CE/FDA approved phantom is a robust quality assurance device. In a multi-center setting, T1 mapping had performance differences between field strengths, sequences, scanner software versions, and manufacturers. However, several specific combinations of field strength, sequence, and scanner are highly repeatable, and thus, have potential to provide standardized assessment of T1 times for clinical use, although temperature correction is required for native T1 tubes at least.


Assuntos
Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/normas , Imagens de Fantasmas/normas , Consenso , Humanos , Variações Dependentes do Observador , Valor Preditivo dos Testes , Reprodutibilidade dos Testes
11.
AJR Am J Roentgenol ; 215(2): 382-389, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32432909

RESUMO

OBJECTIVE. The purposes of this study were to evaluate the outcome of new arterial phase enhancing nodules at MRI of cirrhotic livers, including clinical and imaging factors that affect progression to hepatocellular carcinoma (HCC), and to assess the diagnostic performance of Liver Imaging Reporting and Data System version 2018 (LI-RADSv2018) versus version 2017 (LI-RADSv2017) in categorizing these nodules. MATERIALS AND METHODS. A database search identified 129 new arterial phase enhancing, round, solid, space-occupying nodules in 79 patients with cirrhosis who underwent surveillance MRI. Three readers assessed the nodules for LI-RADS findings and made assessments based on the 2017 and 2018 criteria. Clinical information and laboratory values were collected. Outcome data were assessed on the basis of follow-up imaging and pathology results. Interreader agreement was assessed. Logistic regression and ROC curve analyses were used to assess the utility of the features for prediction of progression to HCC. RESULTS. Of the 129 nodules, 71 (55%) progressed to HCC. LI-RADSv2017 score, LIRADSv2018 score, and mild-to-moderate T2 hyperintensity were significant independent predictors of progression to HCC in univariate analyses. Serum α-fetoprotein level, hepatitis B or C virus infection as the cause of liver disease, and presence of other HCCs were significant predictors of progression to HCC in multivariate analyses. The rates of progression of LI-RADS category 3 and 4 observations were 38.1% and 57.6%, respectively, for LI-RADSv2017 and 44.4% and 69.9%, respectively, for LI-RADSv2018. CONCLUSION. New arterial phase enhancing nodules in patients with cirrhosis frequently progress to HCC. Factors such as serum α-fetoprotein level and presence of other HCCs are strong predictors of progression to HCC.


Assuntos
Carcinoma Hepatocelular/diagnóstico por imagem , Carcinoma Hepatocelular/etiologia , Cirrose Hepática/complicações , Cirrose Hepática/diagnóstico por imagem , Neoplasias Hepáticas/diagnóstico por imagem , Neoplasias Hepáticas/etiologia , Fígado/diagnóstico por imagem , Fígado/patologia , Imagem por Ressonância Magnética/métodos , Artérias , Progressão da Doença , Feminino , Humanos , Cirrose Hepática/patologia , Imagem por Ressonância Magnética/instrumentação , Masculino , Pessoa de Meia-Idade , Projetos de Pesquisa , Estudos Retrospectivos
12.
Sensors (Basel) ; 20(7)2020 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-32260376

RESUMO

The development of 3D anthropomorphic head and neck phantoms is of crucial and timely importance to explore novel imaging techniques, such as radar-based MicroWave Imaging (MWI), which have the potential to accurately diagnose Cervical Lymph Nodes (CLNs) in a neoadjuvant and non-invasive manner. We are motivated by a significant diagnostic blind-spot regarding mass screening of LNs in the case of head and neck cancer. The timely detection and selective removal of metastatic CLNs will prevent tumor cells from entering the lymphatic and blood systems and metastasizing to other body regions. The present paper describes the developed phantom generator which allows the anthropomorphic modelling of the main biological tissues of the cervical region, including CLNs, as well as their dielectric properties, for a frequency range from 1 to 10 GHz, based on Magnetic Resonance images. The resulting phantoms of varying complexity are well-suited to contribute to all stages of the development of a radar-based MWI device capable of detecting CLNs. Simpler models are essential since complexity could hinder the initial development stages of MWI devices. Besides, the diversity of anthropomorphic phantoms resulting from the developed phantom generator can be explored in other scientific contexts and may be useful to other medical imaging modalities.


Assuntos
Cabeça/diagnóstico por imagem , Imageamento de Micro-Ondas , Pescoço/diagnóstico por imagem , Imagens de Fantasmas , Humanos , Imageamento Tridimensional , Imagem por Ressonância Magnética/instrumentação
13.
Cancer Radiother ; 24(5): 398-402, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32247688

RESUMO

Computed tomography (CT) in the treatment position is currently indispensable for planning radiation therapy. Other imaging modalities, such as magnetic resonance imaging (MRI) and positron emission-tomography (PET), can be used to improve the definition of the tumour and/or healthy tissue but also to provide functional data of the target volume. Accurate image registration is essential for treatment planning, so MRI and PET scans should be registered at the planning CT scan. Hybrid PET/MRI scans with a hard plane can be used but pose the problem of the absence of CT scans. Finally, techniques for moving the patient on a rigid air-cushioned table allow PET/CT/MRI scans to be performed in the treatment position while limiting the patient's movements exist. At the same time, the advent of MRI-linear accelerator systems allows to redefine image-guided radiotherapy and to propose treatments with daily recalculation of the dose. The place of PET during treatment remains more confidential and currently only in research and prototype status. The same development of imaging during radiotherapy is underway in proton therapy.


Assuntos
Imagem por Ressonância Magnética/métodos , Imagem Multimodal/métodos , Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Tomografia por Emissão de Pósitrons/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Humanos , Imagem por Ressonância Magnética/instrumentação , Imagem Multimodal/instrumentação , Tomografia por Emissão de Pósitrons/instrumentação , Terapia com Prótons/métodos , Planejamento da Radioterapia Assistida por Computador/instrumentação
14.
PLoS One ; 15(4): e0221071, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32275668

RESUMO

PURPOSE: To accelerate the acquisition of free-breathing 3D saturation-recovery-based (SASHA) myocardial T1 mapping by acquiring fewer saturation points in combination with a post-processing 3D denoising technique to maintain high accuracy and precision. METHODS: 3D SASHA T1 mapping acquires nine T1-weighted images along the saturation recovery curve, resulting in long acquisition times. In this work, we propose to accelerate conventional cardiac T1 mapping by reducing the number of saturation points. High T1 accuracy and low standard deviation (as a surrogate for precision) is maintained by applying a 3D denoising technique to the T1-weighted images prior to pixel-wise T1 fitting. The proposed approach was evaluated on a T1 phantom and 20 healthy subjects, by varying the number of T1-weighted images acquired between three and nine, both prospectively and retrospectively. Following the results from the healthy subjects, three patients with suspected cardiovascular disease were acquired using five T1-weighted images. T1 accuracy and precision was determined for all the acquisitions before and after denoising. RESULTS: In the T1 phantom, no statistical difference was found in terms of accuracy and precision for the different number of T1-weighted images before or after denoising (P = 0.99 and P = 0.99 for accuracy, P = 0.64 and P = 0.42 for precision, respectively). In vivo, both prospectively and retrospectively, the precision improved considerably with the number of T1-weighted images employed before denoising (P<0.05) but was independent on the number of T1-weighted images after denoising. CONCLUSION: We demonstrate the feasibility of accelerating 3D SASHA T1 mapping by reducing the number of acquired T1-weighted images in combination with an efficient 3D denoising, without affecting accuracy and precision of T1 values.


Assuntos
Doenças Cardiovasculares/diagnóstico por imagem , Coração/diagnóstico por imagem , Imageamento Tridimensional/métodos , Imagem por Ressonância Magnética/métodos , Humanos , Imageamento Tridimensional/economia , Imageamento Tridimensional/instrumentação , Imagem por Ressonância Magnética/economia , Imagem por Ressonância Magnética/instrumentação , Imagens de Fantasmas , Estudos Retrospectivos
15.
Med Phys ; 47(7): 3054-3063, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32277703

RESUMO

INTRODUCTION: This work describes the development of a novel radiomics phantom designed for magnetic resonance imaging (MRI) that can be used in a multicenter setting. The purpose of this study is to assess the stability and reproducibility of MRI-based radiomic features using this phantom across different MRI scanners. METHODS & MATERIALS: A set of phantoms were three-dimensional (3D) printed using MRI visible materials. One set of phantoms were imaged on seven MRI scanners and one was imaged on one MRI scanner. Radiomics analysis of the phantoms, which included first-order features, shape and texture features was performed. Intraclass correlation coefficient (ICC) was used to assess the stability of radiomic features across eight scanners and the reproducibility of two printed models on one scanner. Coefficient of variation (COV) was used to assess the reproducibility of radiomics measurements in the phantom on a single scanner. RESULTS: The phantom models provide sufficient signal-to-noise and contrast in all the tumor models permitting robust automatic segmentation. During a 12-month period of monitoring, the phantom material was stable with T1 and T2 of 150.7 ± 6.7 ms and 56.1 ± 3.9 ms, respectively. Of all the radiomic features computed, 34 of 69 had COV < 10%. Features from first-order statistics were the most robust in stability across the eight scanners with eight of 12 (67%) having high stability. About 29 of 50 (58%) texture features had high stability and no shape features had high stability features across the eight scanners. CONCLUSION: A novel MRI radiomics phantom has been developed to assess the reproducibility and stability of MRI-based radiomic features across multiple institutions. The variation in radiomic feature stability demonstrates the need for caution when interpreting these features for clinical studies.


Assuntos
Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética/instrumentação , Imagens de Fantasmas , Impressão Tridimensional , Reprodutibilidade dos Testes
16.
Arterioscler Thromb Vasc Biol ; 40(5): 1123-1134, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32237905

RESUMO

Cardiovascular disease due to atherosclerosis is still the main cause of morbidity and mortality worldwide. This disease is a complex systemic disorder arising from a network of pathological processes within the arterial vessel wall, and, outside of the vasculature, in the hematopoietic system and organs involved in metabolism. Recent years have seen tremendous efforts in the development and validation of quantitative imaging technologies for the noninvasive evaluation of patients with atherosclerotic cardiovascular disease. Specifically, the advent of combined positron emission tomography and magnetic resonance imaging scanners has opened new exciting opportunities in cardiovascular imaging. In this review, we will describe how combined positron emission tomography/magnetic resonance imaging scanners can be leveraged to evaluate atherosclerotic cardiovascular disease at the whole-body level, with specific focus on preclinical animal models of disease, from mouse to nonhuman primates. We will broadly describe 3 major areas of application: (1) vascular imaging, for advanced atherosclerotic plaque phenotyping and evaluation of novel imaging tracers or therapeutic interventions; (2) assessment of the ischemic heart and brain; and (3) whole-body imaging of the hematopoietic system. Finally, we will provide insights on potential novel technical developments which may further increase the relevance of integrated positron emission tomography/magnetic resonance imaging in preclinical atherosclerosis studies.


Assuntos
Aterosclerose/diagnóstico por imagem , Imagem por Ressonância Magnética , Tomografia por Emissão de Pósitrons , Imagem Corporal Total/métodos , Animais , Aterosclerose/patologia , Aterosclerose/terapia , Modelos Animais de Doenças , Desenho de Equipamento , Imagem por Ressonância Magnética/instrumentação , Camundongos , Imagem Multimodal , Tomografia por Emissão de Pósitrons/instrumentação , Valor Preditivo dos Testes , Primatas , Reprodutibilidade dos Testes , Imagem Corporal Total/instrumentação
17.
Phys Med Biol ; 65(11): 115005, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32268314

RESUMO

Prostate cancer is one of the most common cancers among men and its early detection is critical for its successful treatment. The use of multimodal imaging, such as MR-PET, is most advantageous as it is able to provide detailed information about the prostate. However, as the human prostate is flexible and can move into different positions under external conditions, it is important to localise the focused region-of-interest using both MRI and PET under identical circumstances. In this work, we designed five commonly used linear and quadrature radiofrequency surface coils suitable for hybrid MR-PET use in endorectal applications. Due to the endorectal design and the shielded PET insert, the outer face of the coils investigated was curved and the region to be imaged was outside the volume of the coil. The tilting angles of the coils were varied with respect to the main magnetic field direction. This was done to approximate the various positions from which the prostate could be imaged. The transmit efficiencies and safety excitation efficiencies from simulations, together with the signal-to-noise ratios from the MR images were calculated and analysed. Overall, it was found that the overlapped loops driven in quadrature were superior to the other types of coils we tested. In order to determine the effect of the different coil designs on PET, transmission scans were carried out, and it was observed that the differences between attenuation maps with and without the coils were negligible. The findings of this work can provide useful guidance for the integration of such coil designs into MR-PET hybrid systems in the future.


Assuntos
Imagem por Ressonância Magnética/instrumentação , Imagem Multimodal/instrumentação , Tomografia por Emissão de Pósitrons/instrumentação , Neoplasias da Próstata/diagnóstico por imagem , Humanos , Imagem por Ressonância Magnética/métodos , Masculino , Imagem Multimodal/métodos , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons/métodos , Ondas de Rádio , Razão Sinal-Ruído
18.
Phys Med Biol ; 65(10): 105004, 2020 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-32235074

RESUMO

Recent developments in magnetic resonance (MR) to synthetic computed tomography (sCT) conversion have shown that treatment planning is possible without an initial planning CT. Promising conversion results have been demonstrated recently using conditional generative adversarial networks (cGANs). However, the performance is generally only tested on images from one MR scanner, which neglects the potential of neural networks to find general high-level abstract features. In this study, we explored the generalizability of the generator models, trained on a single field strength scanner, to data acquired with higher field strengths. T2-weighted 0.35T MRIs and CTs from 51 patients treated for prostate (40) and cervical cancer (11) were included. 25 of them were used to train four different generators (SE-ResNet, DenseNet, U-Net, and Embedded Net). Further, an ensemble model was created from the four network outputs. The models were validated on 16 patients from a 0.35T MR scanner. Further, the trained models were tested on the Gold Atlas dataset, containing T2-weighted MR scans of different field strengths; 1.5T(7) and 3T(12), and 10 patients from the 0.35T scanner. The sCTs were dosimetrically compared using clinical VMAT plans for all test patients. For the same scanner (0.35T), the results from the different models were comparable on the test set, with only minor differences in the mean absolute error (MAE) (35-51HU body). Similar results were obtained for conversions of 3T GE Signa and the 3T GE Discovery images (40-62HU MAE) for three of the models. However, larger differences were observed for the 1.5T images (48-65HU MAE). The overall best model was found to be the ensemble model. All dose differences were below 1%. This study shows that it is possible to generalize models trained on images of one scanner to other scanners and different field strengths. The best metric results were achieved by the combination of all networks.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/instrumentação , Tomografia Computadorizada por Raios X , Humanos , Masculino , Redes Neurais de Computação , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Radiometria , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada
19.
Phys Med Biol ; 65(12): 125008, 2020 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-32340015

RESUMO

We are building a high sensitivity preclinical PET/MRI insert using a highly multiplexed light sharing PET module. Each module incorporates four 19 × 19 arrays of 1 × 1 × 20 mm3 LYSO crystals with dual-ended DOI encoding readout, requiring 32 readout channels for positioning and eight channels for timing. These constraints necessitate compact, robust electronics for digitization. We have characterized four linearized time-over-threshold circuits based on these detector requirements. The four circuits allow for high channel density and can digitize signals from highly multiplexed light sharing detectors. Each circuit digitizes one channel of a multiplexed SiPM array, yielding a binary output that interfaces directly with an FPGA. Using the optimal circuit, we have characterized the performance of a pair of PET modules. The four circuits were characterized based on linearity of the 22Na photopeak positions and energy resolution at 511 keV, as well as separation of elements in a 10 × 10 array of 1.2 mm LYSO crystals coupled with a specular reflector. Practical measures of performance were comparable to those obtained with a DRS evaluation board, which served as a reference acquisition system. The ratio of the 22Na photopeak positions was 2.0 for each circuit and the reference system, implying 20% saturation due to the SiPM. PET energy resolution of the optimal circuit was 11.8% FWHM for a single crystal versus 12.6% for the reference system, and crystals were equally well separated in all cases. PCBs implementing the optimal readout circuit were fabricated and used to construct two complete detector modules. Crystals in each of the four blocks in the module were well resolved, with a mean energy resolution of 24.4 ± 4.7%. Two modules operating in coincidence showed a single detector timing resolution of 3.0 ns, which is appropriate for preclinical applications.


Assuntos
Imagem por Ressonância Magnética/instrumentação , Tomografia por Emissão de Pósitrons/instrumentação , Eletrônica
20.
Rev Sci Instrum ; 91(2): 024102, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32113406

RESUMO

The dependence of the nuclear magnetic resonance relaxation rate on the magnetic field has been widely studied, in particular, in biomedical areas with the objectives to better understand the underlying microscopic mechanisms in tissues and provide biomarkers of diseases. By combining fast-field cycling (FFC) and magnetic resonance imaging (MRI), it is possible to provide localized relaxation dispersion measurements in heterogeneous systems with recent demonstrations in solutions, biological samples, human beings, and small animals. We report here the developments and performances of a device designed for small animal FFC-MRI comprising a resistive insert technology operating inside a 1.5 T MRI system. Specific measurement methods were developed to characterize the system efficiency, response time, homogeneity, stability, and compensation. By adding a non-linear element in the system and using a dual amplifier strategy, it is shown that large field offsets can be produced during relaxation periods while maintaining precise field control during detection periods. The measurement of longitudinal nuclear magnetic relaxation dispersion (NMRD) profiles in the range of 1.08 T-1.92 T is reported, essentially displaying a linear variation in this range for common MRI contrast agents. The slopes of both the longitudinal and transverse relaxation dispersion profiles at 1.5 T are measured and validated, extending the capabilities of previous approaches. The performances of a longitudinal relaxation dispersion mapping method are finally reported, opening the way to quantitative preclinical dispersion imaging studies at a high FFC-MRI field.


Assuntos
Imagem por Ressonância Magnética/instrumentação , Calibragem , Desenho de Equipamento , Fatores de Tempo
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