Optimizing the management of hereditary haemochromatosis: the value of MRI R2* quantification to predict and monitor body iron stores

This study was supported by a research Grant from the Teaching and Research Department of Centro Hospitalar do Porto (grant number DEFI:309/12(213-DEFI/251-CES). The funder had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript

Tissue iron quantification in chronic liver diseases using MRI shows a relationship between iron accumulation in liver, spleen, and bone marrow

Aim: To investigate iron loading within the liver, pancreas, spleen, and bone marrow using magnetic resonance imaging (MRI) transverse relaxation rate (R2*), in patients with diffuse liver diseases; to evaluate the relationships between iron accumulation in these tissue compartments; and to assess the association between tissue iron overload and the pattern of hepatic cellular iron distribution (hepatocytes versus Kupffer cells). Material and methods: Fifty-six patients with diffuse liver diseases had MRI-derived R2* values, using a multi-echo chemical-shift encoded MRI sequence, of the liver, pancreas, spleen, and vertebral bone marrow. All patients had liver biopsy samples scored for hepatic iron grading (0–4) and iron cellular distribution (within hepatocytes only or within both hepatocytes and Kupffer cells). Results: Liver R2* increased with histological iron grade (RS=0.58, p<0.001) and correlated with spleen (RS=0.71, p<0.001) and bone marrow R2* (RS=0.66, p<0.001), but not with pancreatic R2* (RS=0.22, p=0.096). Splenic and bone marrow R2* values were also correlated (RS=0.72, p<0.001). Patients with iron inside Kupffer cells had the highest R2* in liver, spleen and bone marrow. Conclusions: Patients with chronic diffuse liver diseases have concomitant hepatic, splenic, and bone marrow iron loading. The highest hepatic iron scores and iron inside Kupffer cells were associated with the highest splenic and bone marrow deposits, suggesting systemic iron accumulation in the mononuclear phagocytic system.The present study was supported by the Teaching and Research Department of Centro Hospitalar do Porto with a research grant number DEFI:309/12(213-DEFI/251-CES). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. L.M.B. and A.A.B. are co-founders of QUIBIM SME

Segmentación de imágenes de resonancia magnética en contraste de fase para el estudio de la dinámica del líquido cefalorraquídeo perimedular

La imagen de resonancia magnética en contraste de fase permite estudiar la dinámica del líquido cefalorraquídeo (LCR) perimedular de manera cuantitativa. Sin embargo la anatomía propia del espacio subaracnoideo dificulta la segmentación del LCR debido a la presencia de estructuras vasculares y nervios raquídeos. El objetivo de este trabajo es describir un método de segmentación semiautomático para el estudio de la dinámica del LCR perimedular. El proceso se inicializa con un punto semilla dentro de la región a analizar. El algoritmo crea un mapa de correlación, calcula un valor de umbral y clasifica píxeles de LCR combinando diversas características temporales del comportamiento del flujo como atributos de entrada a un algoritmo k-medias. Un observador llevó a cabo 10 veces la segmentación en 5 sujetos sanos y se calculó el volumen por ciclo y el área en el espacio perimedular C2C3. Las variaciones de las medidas fueron evaluadas como una estimación de la reproducibilidad del método. Para esto se calculó el coeficiente de variación. La variabilidad de las medidas fue menor del 5%. El método facilita la cuantificación del LCR perimedular. En 16 sujetos sanos se cuantificó el volumen por ciclo de LCR y el área en el espacio C2C3 y cisterna prepontina

Accurate simultaneous quantification of liver steatosis and iron overload in diffuse liver diseases with MRI

Purpose: To evaluate the diagnostic performances of 3 Tesla multi-echo chemical shift-encoded gradient echo magnetic resonance (MECSE-MR) imaging to simultaneously quantify liver steatosis and iron overload in a wide spectrum of diffuse liver diseases having biopsy as reference standard. Methods: MECSE-MR-acquired images were used to calculate fat fraction and iron content in a single breath-hold in 109 adult patients. Proton density fat fraction (PDFF) was prospectively estimated using complex-based data reconstruction with multipeak fat modeling. Water R2* was used to estimate iron content. Biopsy was obtained in all cases, grading liver steatosis, siderosis, inflammation, and fibrosis. Differences in PDFF and R2* values across histopathological grades were analyzed, and ROC curves analyses evaluated the MR diagnostic performance. Results: Calculated fat fraction measurements showed significant differences (p < 0.001) among steatosis grades, being unaffected by the presence of inflammation or fibrosis (p ≥ 0.05). A strong correlation was found between fat fraction and steatosis grade (R S = 0.718, p < 0.001). Iron deposits did not affect fat fraction quantitation (p ≥ 0.05), except in cases with severe iron overload (grade 4). A strong positive correlation was also observed between R2* measurements and iron grades (R S = 0.704, p < 0.001). Calculated R2* values were not different across grades of steatosis, inflammation, and fibrosis (p ≥ 0.05). Conclusion: A MECSE-MR sequence simultaneously quantifies liver steatosis and siderosis, regardless coexisting liver inflammation or fibrosis, with high accuracy in a wide spectrum of diffuse liver disorders. This sequence can be acquired within a single breath-hold and can be implemented in the routine MR evaluation of the liver.This work was partially funded by a research grant from the Teaching and Research Department of Centro Hospitalar do Porto (DEFI:309/12(213-DEFI/251-CES)) and from a Spanish Ministry of Health and Carlos III Health Institute funding grant (PI12/01262). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Predicción de la activación neuronal en estimulación tónica en la terapia de EME: uso de modelos 3D de médula espinal personalizados al paciente frente a modelos generalizados

[ES] La terapia de Estimulación de Médula Espinal (EME) es una técnica utilizada para el tratamiento del dolor crónico. En estimulación tónica, el objetivo es estimular las fibras sensitivas Aß que se encuentran en los cordones posteriores de la médula espinal. Esta estimulación produce una sensación de parestesia que bloquea la señal del dolor. Sin embargo, el 35% de los pacientes perciben una estimulación molesta, pues los cambios posturales, la migración de los electrodos o una incorrecta posición de los mismos produce cambios en la parestesia. En los últimos 40 años se han desarrollado modelos computacionales de médula espinal generalizados que permiten entender mejor el efecto de los parámetros de estimulación y de la geometría de los electrodos en la activación neuronal. Pero, el avance hacia una medicina personalizada obliga a desarrollar modelos computacionales personalizados al paciente para optimizar la estimulación de forma individual. Para conocer las ventajas de usar un modelo personalizado frente a uno generalizado, en este estudio se ha comparado la predicción de la activación neuronal y de los parámetros de estimulación que se obtiene de ambos modelos con un caso real. Los resultados muestran que el modelo personalizado predice de forma más aproximada la activación neuronal y, por tanto, el efecto de la estimulación en un paciente. Por tanto, el uso de modelos personalizados podría suponer en un futuro la mejora de la eficacia de la terapia, pues se podría optimizar la programación y la posición de los electrodos antes del implante del sistema de EMESolanes, C.; Durá, JL.; Canós, MA.; De Andres, J.; Martí-Bonmatí, L.; Saiz Rodríguez, FJ. (2020). Predicción de la activación neuronal en estimulación tónica en la terapia de EME: uso de modelos 3D de médula espinal personalizados al paciente frente a modelos generalizados. Sociedad Española de Ingeniería Biomédica. 306-309. http://hdl.handle.net/10251/167126S30630

Evaluation of fibrosis and inflammation in diffuse liver diseases using intravoxel incoherent motion diffusion-weighted MR imaging

Purpose: The purpose of the study was to evaluate the role of intravoxel incoherent motion (IVIM) diffusion model for the assessment of liver fibrosis and inflammation in diffuse liver disorders, also considering the presence of liver steatosis and iron deposits. Methods: Seventy-four patients were included, with liver biopsy and a 3 Tesla abdominal magnetic resonance imaging examination, with an IVIM diffusion-weighted sequence (single-shot spin-echo echo-planar sequence, with gradient reversal fat suppression; 6 b-values: 0, 50, 200, 400, 600, and 800 s/mm2). Histological evaluation comprised the Ishak modified scale, for grading inflammation and fibrosis, plus steatosis and iron loading classification. The liver apparent diffusion coefficient (ADC) and IVIM parameters (D, D*, f) were calculated from the IVIM images. The relationship between IVIM parameters and histopathological scores were evaluated by ANOVA and Spearman correlation tests. A test-retest experiment assessed reproducibility and repeatability in 10 healthy volunteers and 10 randomly selected patient studies. Results: ADC and f values were lower with higher fibrosis stages (p = 0.009, p = 0.006, respectively) and also with higher necro-inflammatory activity grades (p = 0.02, p = 0.017, respectively). Considered together, only fibrosis presented a significant effect on ADC and f measurements (p 0.05). A mild correlation was found between ADC and f with fibrosis (R S = -0.32 and R S = -0.38; p < 0.05) and inflammation (R S = -0.31 and R S = -0.32, p < 0.05; respectively). The AUROC for ADC and f measurements with the different dichotomizations between fibrosis or inflammation grades were only fair (0.670 to 0.749, p < 0.05). Neither D nor D* values were significantly different between liver fibrosis or inflammation grades. D measurements were significantly different across histologic grades of steatosis (p < 0.001) and iron overload (p < 0.001), whereas f measurements showed significant differences across histologic steatosis grades (p = 0.005). There was an excellent agreement between the different readers for ADC, f, and D. Conclusions: Although fibrosis presented a significant effect on ADC and f, IVIM measurements are not accurate enough to stage liver fibrosis or necro-inflammatory activity in diffuse liver diseases. D values were influenced by steatosis and iron overload.This work was partially funded by a research Grant from the Teaching and Research Department of Centro Hospitalar do Porto (DEFI:309/12(213-DEFI/251-CES)) and from a Spanish Ministry of Health and Carlos III Health Institute funding grant (PI12/01262). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Prostate Diffusion Weighted-Magnetic Resonance Image analysis using Multivariate Curve Resolution methods

[EN] Multivariate Curve Resolution (MCR) has been applied on prostate Diffusion Weighted-Magnetic Resonance Images (DW-MRI). Different physiological-based modeling approaches of the diffusion process have been submitted to validation by sequentially incorporating prior knowledge on the MCR constraints. Results validate the biexponential diffusion modeling approach and show the capability of the MCR models to find, characterize and locate the behaviors related to the presence of an early prostate tumor.The authors want to thank prof. Anna de Juan for her comments and help in using the software for this study. This research work was partially supported by the Spanish Ministry of Economy and Competitiveness under the project DPI 2011-28112-004-02.Aguado Sarrió, E.; Prats-Montalbán, JM.; Sanz Requena, R.; Marti Bonmati, L.; Alberich Bayarri, Á.; Ferrer Riquelme, AJ. (2015). Prostate Diffusion Weighted-Magnetic Resonance Image analysis using Multivariate Curve Resolution methods. Chemometrics and Intelligent Laboratory Systems. 140:43-48. https://doi.org/10.1016/j.chemolab.2014.11.002S434814

Portable magnetic resonance imaging of patients indoors, outdoors and at home

Mobile medical imaging devices are invaluable for clinical diagnostic purposes both in and outside healthcare institutions. Among the various imaging modalities, only a few are readily portable. Magnetic resonance imaging (MRI), the gold standard for numerous healthcare conditions, does not traditionally belong to this group. Recently, low-field MRI start-up companies have demonstrated the first decisive steps towards portability within medical facilities, but these are so far incompatible with more demanding use cases such as in remote and developing regions, sports facilities and events, medical and military camps, or home healthcare. Here we present in vivo images taken with a light, home-made, low-field extremity MRI scanner outside the controlled environment provided by medical facilities. To demonstrate the true portability of the system and benchmark its performance in various relevant scenarios, we have acquired images of a volunteer's knee in: i) an MRI physics laboratory; ii) an office room; iii) outside a campus building, connected to a nearby power outlet; iv) in open air, powered from a small fuel-based generator; and v) at the volunteer's home. All images have been acquired within clinically viable times, and signal-to-noise ratios (SNR) and tissue contrast suffice for 2D and 3D reconstructions with diagnostic value, with comparable overall image quality across all five situations. Furthermore, the volunteer carries a fixation metallic implant screwed to the femur, which leads to strong artifacts in standard clinical systems but appears sharp in our low-field acquisitions. Altogether, this work opens a path towards highly accessible MRI under circumstances previously unrealistic.Comment: 17 pages, 4 figures, comments welcom