Systematic method for morphological reconstruction of the semicircular canals using a fully automatic skeletonization process

We present a novel method to characterize the morphology of semicircular canals of the inner ear. Previous experimental works have a common nexus, the human-operator subjectivity. Although these methods are mostly automatic, they rely on a human decision to determine some particular anatomical positions. We implement a systematic analysis where there is no human subjectivity. Our approach is based on a specific magnetic resonance study done in a group of 20 volunteers. From the raw data, the proposed method defines the centerline of all three semicircular canals through a skeletonization process and computes the angle of the functional pair and other geometrical parameters. This approach allows us to assess the inter-operator effect on other methods. From our results, we conclude that, although an average geometry can be defined, the inner ear anatomy cannot be reduced to a single geometry as seen in previous experimental works. We observed a relevant variability of the geometrical parameters in our cohort of volunteers that hinders this usual simplification

Multiparametric renal magnetic resonance imaging: A reproducibility study in renal allografts with stable function

Monitoring renal allograft function after transplantation is key for the early detection of allograft impairment, which in turn can contribute to preventing the loss of the allograft. Multiparametric renal MRI (mpMRI) is a promising noninvasive technique to assess and characterize renal physiopathology; however, few studies have employed mpMRI in renal allografts with stable function (maintained function over a long time period). The purposes of the current study were to evaluate the reproducibility of mpMRI in transplant patients and to characterize normal values of the measured parameters, and to estimate the labeling efficiency of Pseudo-Continuous Arterial Spin Labeling (PCASL) in the infrarenal aorta using numerical simulations considering experimental measurements of aortic blood flow profiles. The subjects were 20 transplant patients with stable kidney function, maintained over 1 year. The MRI protocol consisted of PCASL, intravoxel incoherent motion, and T1 inversion recovery. Phase contrast was used to measure aortic blood flow. Renal blood flow (RBF), diffusion coefficient (D), pseudo-diffusion coefficient (D*), flowing fraction ( f ), and T1 maps were calculated and mean values were measured in the cortex and medulla. The labeling efficiency of PCASL was estimated from simulation of Bloch equations. Reproducibility was assessed with the within-subject coefficient of variation, intraclass correlation coefficient, and Bland-Altman analysis. Correlations were evaluated using the Pearson correlation coefficient. The significance level was p less than 0.05. Cortical reproducibility was very good for T1, D, and RBF, moderate for f , and low for D*, while medullary reproducibility was good for T1 and D. Significant correlations in the cortex between RBF and f (r = 0.66), RBF and eGFR (r = 0.64), and D* and eGFR (r = -0.57) were found. Normal values of the measured parameters employing the mpMRI protocol in kidney transplant patients with stable function were characterized and the results showed good reproducibility of the techniques

Consensus-based technical recommendations for clinical translation of renal phase contrast MRI

Background Phase-contrast (PC) MRI is a feasible and valid noninvasive technique to measure renal artery blood flow, showing potential to support diagnosis and monitoring of renal diseases. However, the variability in measured renal blood flow values across studies is large, most likely due to differences in PC-MRI acquisition and processing. Standardized acquisition and processing protocols are therefore needed to minimize this variability and maximize the potential of renal PC-MRI as a clinically useful tool.Purpose To build technical recommendations for the acquisition, processing, and analysis of renal 2D PC-MRI data in human subjects to promote standardization of renal blood flow measurements and facilitate the comparability of results across scanners and in multicenter clinical studies.Study Type Systematic consensus process using a modified Delphi method.Population Not applicable.Sequence Field/Strength Renal fast gradient echo-based 2D PC-MRI.Assessment An international panel of 27 experts from Europe, the USA, Australia, and Japan with 6 (interquartile range 4-10) years of experience in 2D PC-MRI formulated consensus statements on renal 2D PC-MRI in two rounds of surveys. Starting from a recently published systematic review article, literature-based and data-driven statements regarding patient preparation, hardware, acquisition protocol, analysis steps, and data reporting were formulated.Statistical Tests Consensus was defined as >= 75% unanimity in response, and a clear preference was defined as 60-74% agreement among the experts.Results Among 60 statements, 57 (95%) achieved consensus after the second-round survey, while the remaining three showed a clear preference. Consensus statements resulted in specific recommendations for subject preparation, 2D renal PC-MRI data acquisition, processing, and reporting.Data Conclusion These recommendations might promote a widespread adoption of renal PC-MRI, and may help foster the set-up of multicenter studies aimed at defining reference values and building larger and more definitive evidence, and will facilitate clinical translation of PC-MRI.Level of Evidence 1Technical Efficacy Stage 1Cardiovascular Aspects of Radiolog

RICORS2040 : The need for collaborative research in chronic kidney disease

Chronic kidney disease (CKD) is a silent and poorly known killer. The current concept of CKD is relatively young and uptake by the public, physicians and health authorities is not widespread. Physicians still confuse CKD with chronic kidney insufficiency or failure. For the wider public and health authorities, CKD evokes kidney replacement therapy (KRT). In Spain, the prevalence of KRT is 0.13%. Thus health authorities may consider CKD a non-issue: very few persons eventually need KRT and, for those in whom kidneys fail, the problem is 'solved' by dialysis or kidney transplantation. However, KRT is the tip of the iceberg in the burden of CKD. The main burden of CKD is accelerated ageing and premature death. The cut-off points for kidney function and kidney damage indexes that define CKD also mark an increased risk for all-cause premature death. CKD is the most prevalent risk factor for lethal coronavirus disease 2019 (COVID-19) and the factor that most increases the risk of death in COVID-19, after old age. Men and women undergoing KRT still have an annual mortality that is 10- to 100-fold higher than similar-age peers, and life expectancy is shortened by ~40 years for young persons on dialysis and by 15 years for young persons with a functioning kidney graft. CKD is expected to become the fifth greatest global cause of death by 2040 and the second greatest cause of death in Spain before the end of the century, a time when one in four Spaniards will have CKD. However, by 2022, CKD will become the only top-15 global predicted cause of death that is not supported by a dedicated well-funded Centres for Biomedical Research (CIBER) network structure in Spain. Realizing the underestimation of the CKD burden of disease by health authorities, the Decade of the Kidney initiative for 2020-2030 was launched by the American Association of Kidney Patients and the European Kidney Health Alliance. Leading Spanish kidney researchers grouped in the kidney collaborative research network Red de Investigación Renal have now applied for the Redes de Investigación Cooperativa Orientadas a Resultados en Salud (RICORS) call for collaborative research in Spain with the support of the Spanish Society of Nephrology, Federación Nacional de Asociaciones para la Lucha Contra las Enfermedades del Riñón and ONT: RICORS2040 aims to prevent the dire predictions for the global 2040 burden of CKD from becoming true

Non-invasive evaluation of myocardial perfusion in humans using arterial spin labeling magnetic resonance imaging

Las arterias coronarias son las encargadas de suministrar constantemente oxígeno y nutrientes al corazón. Su estrechamiento u obstrucción causan isquemia y, si no se tratan, provocan la enfermedad isquémica del corazón (CAD), una de las enfermedades cardiovasculares con mayor tasa de mortalidad en Estados Unidos y Europa. La cuantificación de la perfusión miocárdica es un factor clave para el diagnóstico y evaluación de CAD. La perfusión miocárdica se evalúa en resonancia magnética con una técnica de imagen llamada first-pass que requiere de la inyección de un material de contraste basado en Gadolinio, el cual limita la repetibilidad de la técnica y restringe su uso en pacientes con una función renal anormal. Arterial Spin Labeling (ASL) es una técnica de imagen por resonancia magnética que permite cuantificar la perfusión sin necesidad de inyectar un agente de contraste, a través del marcado electromagnético del agua contenida en la sangre arterial, actuando como trazador endógeno. El principal inconveniente de esta técnica es que la magnitud de este trazador es pequeña, debido a la reducida cantidad de sangre marcada por volumen de tejido, y decae con el tiempo de relajación T1. Por tanto, la relación señal/ruido es relativamente baja. Además, su aplicación en el corazón es complicada debido al continuo movimiento y al tortuoso camino que realiza la sangre arterial a través del corazón, lo cual dificulta un marcado preciso. En esta tesis, la técnica ASL (adquisición y procesado de datos) fue optimizada para su utilización en voluntarios sanos y pacientes. En particular, la técnica ASL fue implementada, optimizada y validada en el corazón de sujetos sanos bajo condiciones de reposo y estrés leve mediante el levantamiento pasivo de piernas. Distintas estrategias fueron evaluadas para minimizar el movimiento cardíaco y respiratorio durante la adquisición y el post-procesado de las imágenes de perfusión. Finalmente, la aplicación de la secuencia ASL en el corazón fue evaluada en un grupo de pacientes con sospecha de CAD en condiciones de reposo y vasodilatación farmacológica. La validación de la secuencia miocárdica ASL en voluntarios sanos mostró una mayor eficiencia en el tiempo de adquisición con la utilización de un TR corto de aproximadamente cuatro segundos, el cual proporcionó medidas de reproducibilidad razonables (coeficientes de variación entre sujeto de 17% intrasesión y 37% intersesión). La comparación entre las distintas estrategias de respiración y técnicas de corrección de movimiento mostró la superioridad de la respiración libre en combinación con el método de registro pairwise , resultando en una mayor precisión tras el registro de imágenes sintéticas y mejores resultados de reproducibilidad intrasesión (coeficientes de variación entre sujeto de 14%) junto con una menor variabilidad entre sujetos en la perfusión tras el registro de imágenes reales. Las estrategias de apnea y respiración sincronizada combinadas con el algoritmo de detección de movimiento mostraron resultados similares, pero su aplicación práctica requiere colaboración, lo cual puede ser problemático en pacientes con sospecha de CAD. El estudio clínico ASL demostró la capacidad de la técnica ASL para detectar hiperemia debida a la vasodilatación, para identificar diferencias significativas en la reserva de perfusión miocárdica (MPR) entre segmentos normales e hipoperfundidos y correlaciones de MPR entre ASL y first-pass semicuantitativo, lo que en conjunto sugieren el potencial clínico de la técnica ASL para detectar defectos de perfusión sin el uso de un contraste exógeno

Systematic method for morphological reconstruction of the semicircular canals using a fully automatic skeletonization process

We present a novel method to characterize the morphology of semicircular canals of the inner ear. Previous experimental works have a common nexus, the human-operator subjectivity. Although these methods are mostly automatic, they rely on a human decision to determine some particular anatomical positions. We implement a systematic analysis where there is no human subjectivity. Our approach is based on a specific magnetic resonance study done in a group of 20 volunteers. From the raw data, the proposed method defines the centerline of all three semicircular canals through a skeletonization process and computes the angle of the functional pair and other geometrical parameters. This approach allows us to assess the inter-operator effect on other methods. From our results, we conclude that, although an average geometry can be defined, the inner ear anatomy cannot be reduced to a single geometry as seen in previous experimental works. We observed a relevant variability of the geometrical parameters in our cohort of volunteers that hinders this usual simplification

Systematic method for morphological reconstruction of the semicircular canals using a fully automatic skeletonization process

We present a novel method to characterize the morphology of semicircular canals of the inner ear. Previous experimental works have a common nexus, the human-operator subjectivity. Although these methods are mostly automatic, they rely on a human decision to determine some particular anatomical positions. We implement a systematic analysis where there is no human subjectivity. Our approach is based on a specific magnetic resonance study done in a group of 20 volunteers. From the raw data, the proposed method defines the centerline of all three semicircular canals through a skeletonization process and computes the angle of the functional pair and other geometrical parameters. This approach allows us to assess the inter-operator effect on other methods. From our results, we conclude that, although an average geometry can be defined, the inner ear anatomy cannot be reduced to a single geometry as seen in previous experimental works. We observed a relevant variability of the geometrical parameters in our cohort of volunteers that hinders this usual simplification

Optimization of pseudo‐continuous arterial spin labeling for renal perfusion imaging

Purpose: To evaluate labeling efficiency of pseudo-continuous arterial spin labeling (PCASL) and to find the gradient parameters that increase PCASL robustness for renal perfusion measurements. Methods: Aortic blood flow was characterized in 3 groups: young healthy volunteers (YHV1), chronic kidney disease (CKD) patients (CKDP), and healthy controls (HCO). PCASL inversion efficiency was evaluated through numeric simulations considering the measured pulsatile flow velocity profiles and off-resonance effects for a wide range of gradient parameters, and the results were assessed in vivo. The most robust PCASL implementation was used to measure renal blood flow (RBF) in CKDP and HCO. Results: Aortic blood velocities reached peak values of 120 cm/s in YHV1, whereas for elderly subjects values were lower by approximately a factor of 2. Simulations and experiments showed that by reducing the gradient average (Gave ) and the selective to average gradient ratio (Gmax /Gave ), labeling efficiency was maximized and PCASL robustness to off-resonance was improved. The study in CKDP and HCO showed significant differences in RBF between groups. Conclusion: An efficient and robust PCASL scheme for renal applications requires a Gmax /Gave ratio of 6-7 and a Gave value that depends on the aortic blood flow velocities (0.5 mT/m being appropriate for CKDP and HCO)