scholarly journals MRI Mapping of the Blood Oxygenation Sensitive Parameter T2* in the Kidney: Basic Concept

2021 ◽  
pp. 171-185
Author(s):  
Lu-Ping Li ◽  
Bradley Hack ◽  
Erdmann Seeliger ◽  
Pottumarthi V. Prasad
Keyword(s):  
Data Acquisition ◽  
Blood Oxygenation ◽  
The European Union ◽  
Noninvasive Method ◽  
Bold Mri ◽  
Oxygenation Level ◽  
Technical Issues ◽  
Renal Mri ◽  
The Cost

AbstractThe role of hypoxia in renal disease and injury has long been suggested but much work still remains, especially as it relates to human translation. Invasive pO2 probes are feasible in animal models but not for human use. In addition, they only provide localized measurements. Histological methods can identify hypoxic tissue and provide a spatial distribution, but are invasive and allow only one-time point. Blood oxygenation level dependent (BOLD) MRI is a noninvasive method that can monitor relative oxygen availability across the kidney. It is based on the inherent differences in magnetic properties of oxygenated vs. deoxygenated hemoglobin. Presence of deoxyhemoglobin enhances the spin–spin relaxation rate measured using a gradient echo sequence, known as R2* (= 1/T2*). While the key interest of BOLD MRI is in the application to humans, use in preclinical models is necessary primarily to validate the measurement against invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRI acquisitions in preclinical settings involves several challenges both in terms of logistics and data acquisition. This section will introduce the concept of BOLD MRI and provide some illustrative applications. The following sections will discuss the technical issues associated with data acquisition and analysis.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.

scholarly journals Experimental Protocol for MRI Mapping of the Blood Oxygenation-Sensitive Parameters T2* and T2 in the Kidney

2021 ◽  
pp. 403-417
Author(s):  
Andreas Pohlmann ◽  
Kaixuan Zhao ◽  
Sean B. Fain ◽  
Pottumarthi V. Prasad ◽  
Thoralf Niendorf
Keyword(s):  
Kidney Injury ◽  
Absolute Quantification ◽  
Blood Oxygenation ◽  
The European Union ◽  
Experimental Protocol ◽  
Contrast Mechanism ◽  
Oxygenation Level ◽  
Fraction Of Inspired Oxygen ◽  
Renal Mri

AbstractRenal hypoxia is generally accepted as a key pathophysiologic event in acute kidney injury of various origins, and has also been suggested to play a role in the development of chronic kidney disease. Here we describe a step-by-step experimental protocol for indirect monitoring of renal blood oxygenation in rodents via the deoxyhemoglobin sensitive MR parameters T2* and T2—a contrast mechanism known as the blood oxygenation level dependent (BOLD) effect. Since an absolute quantification of renal oxygenation from T2*/T2 remains challenging, the effects of controlled and standardized variations in the fraction of inspired oxygen are used for bench marking. This MRI method may be useful for investigating renal blood oxygenation of small rodents in vivo under various experimental (patho)physiological conditions.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.

scholarly journals Analysis Protocols for MRI Mapping of the Blood Oxygenation–Sensitive Parameters T2* and T2 in the Kidney

2021 ◽  
pp. 591-610
Author(s):  
João S. Periquito ◽  
Ludger Starke ◽  
Carlota M. Santos ◽  
Andreia C. Freitas ◽  
Nuno Loução ◽  
...  
Keyword(s):  
Data Analysis ◽  
Model Fitting ◽  
Kidney Injury ◽  
Blood Oxygenation ◽  
The European Union ◽  
Contrast Mechanism ◽  
Oxygenation Level ◽  
Quality Checks ◽  
Renal Mri ◽  
Sensitive Parameters

AbstractRenal hypoxia is generally accepted as a key pathophysiologic event in acute kidney injury of various origins and has also been suggested to play a role in the development of chronic kidney disease. Here we describe step-by-step data analysis protocols for MRI monitoring of renal oxygenation in rodents via the deoxyhemoglobin concentration sensitive MR parameters T2* and T2—a contrast mechanism known as the blood oxygenation level dependent (BOLD) effect.This chapter describes how to use the analysis tools provided by vendors of animal and clinical MR systems, as well as how to develop an analysis software. Aspects covered are: data quality checks, data exclusion, model fitting, fitting algorithm, starting values, effects of multiecho imaging, and result validation.This chapter is based upon work from the PARENCHIMA COST Action, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.

scholarly journals Subsegmentation of the Kidney in Experimental MR Images Using Morphology-Based Regions-of-Interest or Multiple-Layer Concentric Objects

2021 ◽  
pp. 549-564
Author(s):  
Leili Riazy ◽  
Bastien Milani ◽  
João S. Periquito ◽  
Kathleen Cantow ◽  
Thoralf Niendorf ◽  
...  
Keyword(s):  
Sodium Concentration ◽  
Magnetic Resonance Images ◽  
Blood Oxygenation ◽  
Regions Of Interest ◽  
The European Union ◽  
Tissue Microstructure ◽  
Renal Mri ◽  
Anatomic Locations ◽  
The Cost ◽  
Changes Over Time

AbstractFunctional renal MRI promises access to a wide range of physiologically relevant parameters such as blood oxygenation, perfusion, tissue microstructure, pH, and sodium concentration. For quantitative comparison of results, representative values must be extracted from the parametric maps obtained with these different MRI techniques. To improve reproducibility of results this should be done based on regions-of-interest (ROIs) that are clearly and objectively defined.Semiautomated subsegmentation of the kidney in magnetic resonance images represents a simple but very valuable approach for the quantitative analysis of imaging parameters in multiple ROIs that are associated with specific anatomic locations. Thereby, it facilitates comparing MR parameters between different kidney regions, as well as tracking changes over time.Here we provide detailed step-by-step instructions for two recently developed subsegmentation techniques that are suitable for kidneys of small rodents: i) the placement of ROIs in cortex, outer and the inner medulla based on typical kidney morphology and ii) the division of the kidney into concentrically oriented layers.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.

scholarly journals Sodium (23Na) MRI of the Kidney: Basic Concept

2021 ◽  
pp. 257-266
Author(s):  
James T. Grist ◽  
Esben Søvsø Hansen ◽  
Frank G. Zöllner ◽  
Christoffer Laustsen
Keyword(s):  
Data Analysis ◽  
Renal Diseases ◽  
The European Union ◽  
Key Indicator ◽  
Sodium Gradient ◽  
Sodium Imaging ◽  
Renal Mri ◽  
The Cost ◽  
Sodium Handling ◽  
23Na Mri

AbstractThe handling of sodium by the renal system is a key indicator of renal function. Alterations in the corticomedullary distribution of sodium are considered important indicators of pathology in renal diseases. The derangement of sodium handling can be noninvasively imaged using sodium magnetic resonance imaging (23Na MRI), with data analysis allowing for the assessment of the corticomedullary sodium gradient. Here we introduce sodium imaging, describe the existing methods, and give an overview of preclinical sodium imaging applications to illustrate the utility and applicability of this technique for measuring renal sodium handling.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.

scholarly journals BOLD MRI to evaluate early development of renal injury in a rat model of diabetes

2018 ◽  
Vol 46 (4) ◽  
pp. 1391-1403 ◽  
Author(s):  
Qidong Wang ◽  
Chuangen Guo ◽  
Lan Zhang ◽  
Rui Zhang ◽  
Zhaoming Wang ◽  
...  
Keyword(s):  
Renal Injury ◽  
Diabetic Rats ◽  
Blood Oxygenation ◽  
Dynamic Changes ◽  
Bold Mri ◽  
Oxygenation Level ◽  
Mri Scans ◽  
Streptozotocin Induced Diabetes ◽  
Magnetic Resonance Imaging Mri ◽  
Diabetes Induction

Objective To investigate changes in renal oxygenation levels by blood-oxygenation-level dependent (BOLD)-magnetic resonance imaging (MRI), and to evaluate BOLD-MRI for detecting early diabetic renal injury. Methods Seventy-five rats, with unilateral nephrectomy, were randomly divided into streptozotocin-induced diabetes mellitus (DM, n = 65) and normal control (NC, n = 10) groups. BOLD-MRI scans were performed at baseline (both groups) and at 3, 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70 days (DM only). Renal cortical (C) and medullary (M) R2* signals were measured and R2* medulla/cortex ratio (MCR) was calculated. Results DM-group CR2* and MR2* values were significantly higher than NC values following diabetes induction. R2* values increased gradually and peaked at day 35 (CR2*, 33.95 ± 0.34 s–1; MR2*, 43.79 ± 1.46 s–1), then dropped gradually (CR2*, 33.17 ± 0.69 s–1; MR2*, 41.61 ± 0.95 s–1 at day 70). DM-group MCR rose gradually from 1.12 to 1.32 at day 42, then decreased to 1.25 by day 70. Conclusions BOLD-MRI can be used to non-invasively evaluate renal hypoxia and early diabetic renal injury in diabetic rats. MCR may be adopted to reflect dynamic changes in renal hypoxia.

scholarly journals The Cumulative Influence of Hyperoxia and Hypercapnia on Blood Oxygenation and R2*

2015 ◽  
Vol 35 (12) ◽  
pp. 2032-2042 ◽  
Author(s):  
Carlos C Faraco ◽  
Megan K Strother ◽  
Jeroen CW Siero ◽  
Daniel F Arteaga ◽  
Allison O Scott ◽  
...  
Keyword(s):  
Venous Blood ◽  
Quantitative Information ◽  
Blood Oxygenation ◽  
Cerebrovascular Reactivity ◽  
Resonance Imaging ◽  
Tissue Water ◽  
Bold Mri ◽  
Bold Imaging ◽  
Complex Interactions ◽  
Oxygenation Level

Cerebrovascular reactivity (CVR)-weighted blood-oxygenation-level-dependent magnetic resonance imaging (BOLD-MRI) experiments are frequently used in conjunction with hyperoxia. Owing to complex interactions between hyperoxia and hypercapnia, quantitative effects of these gas mixtures on BOLD responses, blood and tissue R2∗, and blood oxygenation are incompletely understood. Here we performed BOLD imaging (3T; TE/TR = 35/2,000 ms; spatial resolution = 3×3×3.5 mm3) in healthy volunteers ( n = 12; age = 29±4.1 years) breathing (i) room air (RA), (ii) normocapnic-hyperoxia (95% O2/5% N2, HO), (iii) hypercapnic-normoxia (5% CO2/21% O2/74% N2, HC-NO), and (iv) hypercapnic-hyperoxia (5% CO2/95% O2, HC-HO). For HC-HO, experiments were performed with separate RA and HO baselines to control for changes in O2. T2-relaxation-under-spin-tagging MRI was used to calculate basal venous oxygenation. Signal changes were quantified and established hemodynamic models were applied to quantify vasoactive blood oxygenation, blood–water R∗2, and tissue-water R∗2. In the cortex, fractional BOLD changes (stimulus/baseline) were HO/RA = 0.011 ± 0.007; HC-NO/RA = 0.014±0.004; HC-HO/HO = 0.020±0.008; and HC-HO/RA = 0.035 ±0.010; for the measured basal venous oxygenation level of 0.632, this led to venous blood oxygenation levels of 0.660 (HO), 0.665 (HC-NO), and 0.712 (HC-HO). Interleaving a HC-HO stimulus with HO baseline provided a smaller but significantly elevated BOLD response compared with a HC-NO stimulus. Results provide an outline for how blood oxygenation differs for several gas stimuli and provides quantitative information on how hypercapnic BOLD CVR and R∗2 are altered during hyperoxia.

scholarly journals Quantitative Assessment of Renal Perfusion and Oxygenation by Invasive Probes: Basic Concepts

2021 ◽  
pp. 89-107
Author(s):  
Kathleen Cantow ◽  
Roger G. Evans ◽  
Dirk Grosenick ◽  
Thomas Gladytz ◽  
Thoralf Niendorf ◽  
...  
Keyword(s):  
Kidney Injury ◽  
Tissue Perfusion ◽  
Renal Perfusion ◽  
Renal Tissue ◽  
Acute Injury ◽  
The European Union ◽  
Advantages And Disadvantages ◽  
Tissue Hypoperfusion ◽  
Renal Mri ◽  
The Cost

AbstractRenal tissue hypoperfusion and hypoxia are early key elements in the pathophysiology of acute kidney injury of various origins, and may also promote progression from acute injury to chronic kidney disease. Here we describe basic principles of methodology to quantify renal hemodynamics and tissue oxygenation by means of invasive probes in experimental animals. Advantages and disadvantages of the various methods are discussed in the context of the heterogeneity of renal tissue perfusion and oxygenation.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by a separate chapter describing the experimental procedure and data analysis.

scholarly journals Recommendations for Preclinical Renal MRI: A Comprehensive Open-Access Protocol Collection to Improve Training, Reproducibility, and Comparability of Studies

2021 ◽  
pp. 3-23
Author(s):  
Andreas Pohlmann ◽  
Susan J. Back ◽  
Andrea Fekete ◽  
Iris Friedli ◽  
Stefanie Hectors ◽  
...  
Keyword(s):  
Routine Clinical Practice ◽  
Small Animals ◽  
The European Union ◽  
European Cooperation ◽  
Comprehensive Collection ◽  
Mri Studies ◽  
Quantum Leap ◽  
Renal Mri ◽  
The Cost ◽  
Crucial Part

AbstractRenal MRI holds incredible promise for making a quantum leap in improving diagnosis and care of patients with a multitude of diseases, by moving beyond the limitations and restrictions of current routine clinical practice. Clinical and preclinical renal MRI is advancing with ever increasing rapidity, and yet, aside from a few examples of renal MRI in routine use, it is still not good enough. Several roadblocks are still delaying the pace of progress, particularly inefficient education of renal MR researchers, and lack of harmonization of approaches that limits the sharing of results among multiple research groups.Here we aim to address these limitations for preclinical renal MRI (predominantly in small animals), by providing a comprehensive collection of more than 40 publications that will serve as a foundational resource for preclinical renal MRI studies. This includes chapters describing the fundamental principles underlying a variety of renal MRI methods, step-by-step protocols for executing renal MRI studies, and detailed guides for data analysis. This collection will serve as a crucial part of a roadmap toward conducting renal MRI studies in a robust and reproducible way, that will promote the standardization and sharing of data.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.

scholarly journals Experimental Protocols for MRI Mapping of Renal T1

2021 ◽  
pp. 383-402
Author(s):  
Philippe Garteiser ◽  
Octavia Bane ◽  
Sabrina Doblas ◽  
Iris Friedli ◽  
Stefanie Hectors ◽  
...  
Keyword(s):  
Small Animal ◽  
Water Proton ◽  
The European Union ◽  
Imaging Protocol ◽  
European Cooperation ◽  
Experimental Protocols ◽  
Renal Mri ◽  
Kidney Imaging ◽  
The Cost ◽  
Clinical Scanner

AbstractThe water proton longitudinal relaxation time, T1, is a common and useful MR parameter in nephrology research. Here we provide three step-by-step T1-mapping protocols suitable for different types of nephrology research. Firstly, we provide a single-slice 2D saturation recovery protocol suitable for studies of global pathology, where whole-kidney coverage is unnecessary. Secondly, we provide an inversion recovery type imaging protocol that may be optimized for specific kidney disease applications. Finally, we also provide imaging protocol for small animal kidney imaging in a clinical scanner.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This analysis protocol chapter is complemented by two separate chapters describing the basic concept and experimental procedure.

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