Experimental MRI monitoring of renal blood volume fraction variations en route to renal magnetic resonance oximetry

Diagnosis of early-stage acute kidney injury (AKI) will benefit from a timely identification of local tissue hypoxia. Renal tissue hypoxia is an early feature in AKI pathophysiology, and renal oxygenation is increasingly being assessed through T(2)*-weighted magnetic resonance imaging (MRI). However, changes in renal blood volume fraction (BVf) confound renal T(2)*. The aim of this study was to assess the feasibility of intravascular contrast-enhanced MRI for monitoring renal BVf during physiological interventions that are concomitant with variations in BVf and to explore the possibility of correcting renal T(2)* for BVf variations. A dose-dependent study of the contrast agent ferumoxytol was performed in rats. BVf was monitored throughout short-term occlusion of the renal vein, which is known to markedly change renal blood partial pressure of O(2) and BVf. BVf calculated from MRI measurements was used to estimate oxygen saturation of hemoglobin (SO(2)). BVf and SO(2) were benchmarked against cortical data derived from near-infrared spectroscopy. As estimated from magnetic resonance parametric maps of T(2) and T(2)*, BVf was shown to increase, whereas SO(2) was shown to decline during venous occlusion (VO). This observation could be quantitatively reproduced in test-retest scenarios. Changes in BVf and SO(2) were in good agreement with data obtained from near-infrared spectroscopy. Our findings provide motivation to advance multiparametric MRI for studying AKIs, with the ultimate goal of translating MRI-based renal BVf mapping into clinical practice en route noninvasive renal magnetic resonance oximetry as a method of assessing AKI and progression to chronic damage

Simultaneous T(2) and T(2)* mapping of multiple sclerosis lesions with radial RARE-EPI

PURPOSE: The characteristic MRI features of multiple sclerosis (MS) lesions make it conceptually appealing to pursue parametric mapping techniques that support simultaneous generation of quantitative maps of 2 or more MR contrast mechanisms. We present a modular rapid acquisition with relaxation enhancement (RARE)‐EPI hybrid that facilitates simultaneous T(2) and T(2)* mapping (2in1‐RARE‐EPI). METHODS: In 2in1‐RARE‐EPI the first echoes in the echo train are acquired with a RARE module, later echoes are acquired with an EPI module. To define the fraction of echoes covered by the RARE and EPI module, an error analysis of T(2) and T(2)* was conducted with Monte Carlo simulations. Radial k‐space (under)sampling was implemented for acceleration (R = 2). The feasibility of 2in1‐RARE‐EPI for simultaneous T(2) and T(2)* mapping was examined in a phantom study mimicking T(2) and T(2)* relaxation times of the brain. For validation, 2in1‐RARE‐EPI was benchmarked versus multi spin‐echo (MSE) and multi gradient‐echo (MGRE) techniques. The clinical applicability of 2in1‐RARE‐EPI was demonstrated in healthy subjects and MS patients. RESULTS: There was a good agreement between T(2)/T(2)* values derived from 2in1‐RARE‐EPI and T(2)/T(2)* reference values obtained from MSE and MGRE in both phantoms and healthy subjects. In patients, MS lesions in T(2) and T(2)* maps deduced from 2in1‐RARE‐EPI could be just as clearly delineated as in reference maps calculated from MSE/MGRE. CONCLUSION: This work demonstrates the feasibility of radially (under)sampled 2in1‐RARE‐EPI for simultaneous T(2) and T(2)* mapping in MS patients

Cardiorenal sodium MRI in small rodents using a quadrature birdcage volume resonator at 9.4 T

OBECTIVE: Design, implementation, evaluation and application of a quadrature birdcage radiofrequency (RF) resonator tailored for renal and cardiac sodium ((23)Na) magnetic resonance imaging (MRI) in rats at 9.4 T. MATERIALS AND METHODS: A low pass birdcage resonator (16 rungs, d(in) = 62 mm) was developed. The transmission field (B(1)(+)) was examined with EMF simulations. The scattering parameter (S-parameter) and the quality factor (Q-factor) were measured. For experimental validation B(1)(+)-field maps were acquired with the double-angle method. In vivo sodium imaging of the heart (spatial resolution: (1 × 1 × 5) mm(3)) and kidney (spatial resolution: (1 × 1 × 10) mm(3)) was performed with a FLASH technique. RESULTS: The RF resonator exhibits RF characteristics, transmission field homogeneity and penetration that afford (23)Na MR in vivo imaging of the kidney and heart at 9.4 T. For the renal cortex and medulla a SNRs of 8 and 13 were obtained and a SNRs of 14 and 15 were observed for the left and right ventricle. DISCUSSION: These initial results obtained in vivo in rats using the quadrature birdcage volume RF resonator for (23)Na MRI permit dedicated studies on experimental models of cardiac and renal diseases, which would contribute to translational research of the cardiorenal syndrome

Simulation der Hochtemperaturoxidation von WWER-Brennelementhuellen mit MULTRAN

Available from TIB Hannover: RN 726(741) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel (1)H/(23)Na radiofrequency antenna array

PURPOSE: Cardiorenal syndrome describes disorders of the heart and the kidneys in which a dysfunction of 1 organ induces a dysfunction in the other. This work describes the design, evaluation, and application of a 4/4-channel hydrogen-1/sodium ((1)H/(23)Na) RF array tailored for cardiorenal MRI at 7.0 Tesla (T) for a better physiometabolic understanding of cardiorenal syndrome. METHODS: The dual-frequency RF array is composed of a planar posterior section and a modestly curved anterior section, each section consisting of 2 loop elements tailored for (23)Na MR and 2 loopole-type elements customized for (1)H MR. Numerical electromagnetic field and specific absorption rate simulations were carried out. Transmission field (B(1)(+)) uniformity was optimized and benchmarked against electromagnetic field simulations. An in vivo feasibility study was performed. RESULTS: The proposed array exhibits sufficient RF characteristics, B(1)(+) homogeneity, and penetration depth to perform (23)Na MRI of the heart and kidney at 7.0 T. The mean B(1)(+) field for sodium in the heart is 7.7 ± 0.8 µT/√kW and in the kidney is 6.9 ± 2.3 µT/√kW. The suitability of the RF array for (23)Na MRI was demonstrated in healthy subjects (acquisition time for (23)Na MRI: 18 min; nominal isotropic spatial resolution: 5 mm [kidney] and 6 mm [heart]). CONCLUSION: This work provides encouragement for further explorations into densely packed multichannel transceiver arrays tailored for (23)Na MRI of the heart and kidney. Equipped with this technology, the ability to probe sodium concentration in the heart and kidney in vivo using (23)Na MRI stands to make a critical contribution to deciphering the complex interactions between both organs

Effects of Al-, Ti- and Zn-containing nanomaterials on cell lines in vitro

International audience52nd Congress of the European-Societies-of-Toxicology (EUROTOX), Seville, Spain

Effects of Al-, Ti- and Zn-containing nanomaterials on cell lines in vitro

International audience52nd Congress of the European-Societies-of-Toxicology (EUROTOX), Seville, Spain