scholarly journals The blood oxygen level dependent (BOLD) effect of in-vitro myoglobin and hemoglobin

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dominik P. Guensch ◽  
Matthias C. Michel ◽  
Stefan P. Huettenmoser ◽  
Bernd Jung ◽  
Patrik Gulac ◽  
...  
Keyword(s):  
Chemical Reduction ◽  
T2 Mapping ◽  
Relaxation Times ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygenation ◽  
Blood Oxygen Level ◽  
Bold Effect ◽  
Oxygenation Level ◽  
Magnetic Resonance Imaging Mri

AbstractThe presence of deoxygenated hemoglobin (Hb) results in a drop in T2 and T2* in magnetic resonance imaging (MRI), known as the blood oxygenation level-dependent (BOLD-)effect. The purpose of this study was to investigate if deoxygenated myoglobin (Mb) exerts a BOLD-like effect. Equine Met-Mb powder was dissolved and converted to oxygenated Mb. T1, T2, T2*-maps and BOLD-bSSFP images at 3Tesla were used to scan 22 Mb samples and 12 Hb samples at room air, deoxygenation, reoxygenation and after chemical reduction. In Mb, T2 and T2* mapping showed a significant decrease after deoxygenation (− 25% and − 12%, p < 0.01), increase after subsequent reoxygenation (+ 17% and 0% vs. room air, p < 0.01), and finally a decrease in T2 after chemical reduction (− 28%, p < 0.01). An opposite trend was observed with T1 for each stage, while chemical reduction reduced BOLD-bSSFP signal (− 3%, p < 0.01). Similar deflections were seen at oxygenation changes in Hb. The T1 changes suggests that the oxygen content has been changed in the specimen. The shortening of transverse relaxation times in T2 and T2*-mapping after deoxygenation in Mb specimens are highly indicative of a BOLD-like effect.

scholarly journals Multivoxel Pattern of Blood Oxygen Level Dependent Activity can be sensitive to stimulus specific fine scale responses

2019 ◽  
Author(s):  
Luca Vizioli ◽  
Federico De Martino ◽  
Lucy S Petro ◽  
Daniel Kersten ◽  
Kamil Ugurbil ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygenation ◽  
Support Vector ◽  
Fine Scale ◽  
Blood Oxygen Level ◽  
Linear Discriminant ◽  
Bold Responses ◽  
Oxygenation Level ◽  
Analytical Approaches

1.AbstractAt ultra-high field, fMRI voxels can span the sub-millimeter range, allowing the recording of blood oxygenation level dependent (BOLD) responses at the level of fundamental units of neural computation, such as cortical columns and layers. This sub-millimeter resolution, however, is only nominal in nature as a number of factors limit the spatial acuity of functional voxels. Multivoxel Pattern Analysis (MVPA) may provide a means to detect information at finer spatial scales that may otherwise not be visible at the single voxel level due to limitations in sensitivity and specificity. Here, we evaluate the spatial scale of stimuli specific BOLD responses in multivoxel patterns exploited by linear Support Vector Machine, Linear Discriminant Analysis and Naïve Bayesian classifiers across cortical depths in V1. To this end, we artificially misaligned the testing relative to the training portion of the data in increasing spatial steps, then investigated the breakdown of the classifiers’ performances. A one voxel shift led to a significant decrease in decoding accuracy (p<.05) across all cortical depths, indicating that stimulus specific responses in a multivoxel pattern of BOLD activity exploited by multivariate decoders can be as precise as the nominal resolution of single voxels (here .8 mm isotropic). Our results further indicate that large draining vessels, prominently residing in proximity of the pial surface, do not, in this case, hinder the ability of MVPA to exploit fine scale patterns of BOLD signals. We argue that tailored analytical approaches can help overcoming limitations in high-resolution fMRI and permit studying the mesoscale organization of the human brain with higher sensitivities.

scholarly journals Validating Linear Systems Analysis for Laminar fMRI: Temporal Additivity for Stimulus Duration Manipulations

2020 ◽  
Author(s):  
Jelle A. van Dijk ◽  
Alessio Fracasso ◽  
Natalia Petridou ◽  
Serge O. Dumoulin
Keyword(s):  
Systems Theory ◽  
Linear Systems ◽  
Blood Oxygenation ◽  
Ultra High Field ◽  
Feedback Information ◽  
Oxygenation Level ◽  
Early Visual Cortex ◽  
Magnetic Resonance Imaging Mri ◽  
And Function ◽  
The Relationship

AbstractAdvancements in ultra-high field (7 T and higher) magnetic resonance imaging (MRI) scanners have made it possible to investigate both the structure and function of the human brain at a sub-millimeter scale. As neuronal feedforward and feedback information arrives in different layers, sub-millimeter functional MRI has the potential to uncover information processing between cortical micro-circuits across cortical depth, i.e. laminar fMRI. For nearly all conventional fMRI analyses, the main assumption is that the relationship between local neuronal activity and the blood oxygenation level dependent (BOLD) signal adheres to the principles of linear systems theory. For laminar fMRI, however, directional blood pooling across cortical depth stemming from the anatomy of the cortical vasculature, potentially violates these linear system assumptions, thereby complicating analysis and interpretation. Here we assess whether the temporal additivity requirement of linear systems theory holds for laminar fMRI. We measured responses elicited by viewing stimuli presented for different durations and evaluated how well the responses to shorter durations predicted those elicited by longer durations. We find that BOLD response predictions are consistently good predictors for observed responses, across all cortical depths, and in all measured visual field maps (V1, V2, and V3). Our results suggest that the temporal additivity assumption for linear systems theory holds for laminar fMRI. We thus show that the temporal additivity assumption holds across cortical depth for sub-millimeter gradient-echo BOLD fMRI in early visual cortex.

3 T: the good, the bad and the ugly

2021 ◽  
Author(s):  
Martin John Graves
Keyword(s):  
Signal To Noise Ratio ◽  
Relaxation Times ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen ◽  
Rf Power ◽  
Blood Oxygen Level ◽  
Signal To Noise ◽  
Improve Image Quality ◽  
Mr Physics ◽  
T System

It is around 20 years since the first commercial 3 T MRI systems became available. The theoretical promise of twice the signal-to-noise ratio of a 1.5 T system together with a greater sensitivity to magnetic susceptibility-related contrast mechanisms, such as the blood oxygen level dependent (BOLD) effect that is the basis for functional MRI (fMRI), drove the initial market in neuroradiology. However, the limitations of the increased field strength soon became apparent, including the increased radiofrequency (RF) power deposition, tissue dependent changes in relaxation times, increased artifacts, and greater safety concerns. Many of these issues are dependent upon MR physics and work arounds have had to be developed to try and mitigate their effects. This article reviews the underlying principles of the good, the bad and the ugly aspects of 3 T, discusses some of the methods used to improve image quality and explains the remaining challenges and concerns.

scholarly journals Myocardial Tissue Characterization By T2 Mapping in Thalassemia Major

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 27-28
Author(s):  
Alessia Pepe ◽  
Nicola Martini ◽  
Rita Borrello ◽  
Vincenzo Positano ◽  
Laura Pistoia ◽  
...  
Keyword(s):  
Tissue Characterization ◽  
Spin Echo ◽  
T2 Mapping ◽  
Relaxation Times ◽  
Thalassemia Major ◽  
Fast Spin Echo ◽  
Myocardial Inflammation ◽  
Healthy Population ◽  
Myocardial Iron ◽  
Magnetic Resonance Imaging Mri

Introduction.The presence of iron deposits results in a significant reduction in all magnetic resonance imaging (MRI) relaxation times (T1, T2 and T2*). In the clinical setting the T2* technique is the method of choice for cardiac iron quantification and it has revolutionized the management of patients with hemoglopinopathies. Purpose.To compare myocardial T2 against T2* in patients with thalassemia major (TM) for myocardial iron characterization. Methods.133 TM patients (79 females, 38.4±11.3 years) enrolled in the Extension Myocardial Iron Overload in Thalassemia (eMIOT) Network were considered. T2 and T2* images were acquired, respectively, with multi-echo fast-spin-echo and gradient-echo sequences. Global heart T2 and T2* values were obtained by averaging the values in all 16 myocardial segments. The normal T2 range was established as mean±2 standard deviations on data acquired on 80 healthy volunteers (males: 48-56 ms and females: 50-57 ms). The lower limit of normal for global heart T2*, established on the same healthy population, was 32 ms. Results.A significant correlation was detected between global heart T2 and T2* values (R=0.577; P&lt;0.0001) (Figure). Out of the 113 (84.9%) patients with a normal global heart T2* value, none had a decreased global heart T2 value, while 58 (51.3%) had an increased T2 value. Out of the 20 patents with a decreased global heart T2* value, only 10 (50%) had also a reduced T2 value. Conversely, 9 (45.0%) had a normal global heart T2 value and one (4.5) showed an increased T2 value. The 59 patients with increased global heart T2 value were significantly older than the remaining patients (40.8±10.5 vs 36.4±11.6 years; P=0.019) Conclusion.All patients with decreased T2 value had also a decreased T2* value and in half of the patients iron load was undetected by T2, suggesting that T2 mapping does not offer any advantage in terms of sensitivity for MIO assessment. However, more than half of TM patients had an increased T2 value, thus may be caused by the presence of myocardial inflammation and/or edema. So, T2 mapping could reveal subclinical myocardial involvement in TM patients. Figure Disclosures Pistoia: Chiesi Farmaceutici S.p.A.:Other: speakers' honoraria.Meloni:Chiesi Farmaceutici S.p.A.:Other: speakers' honoraria.

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 Magnetic Resonance Imaging Property of Doxorubicin-Loaded Gadolinium/13X Zeolite/Folic Acid Nanocomposite

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
S Ghaderi
Keyword(s):  
Magnetic Resonance Imaging ◽  
Folic Acid ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
A549 Cells ◽  
In Vitro Study ◽  
Resonance Imaging ◽  
13X Zeolite ◽  
Magnetic Resonance Imaging Mri

Abstract Background: Magnetic resonance imaging (MRI) using nanostructures has been a proper method for tumor targeting purposes. Different MRI nanomaterials, targeting agents and anticancer drugs have been used for targeting of tumors. Objectives: This study aims to consider the MRI property of doxorubicin (DOX)-loaded gadolinium/13X zeolite/folic acid (Gd3+/13X/FA) nanocomposite. Material and Methods: In this in vitro study, Gd3+/13X/FA/DOX nanocomposite was prepared and the X-ray diffraction, scanning electron microscopy and MTT assay were conducted to evaluate the physicochemical properties of the nanocomposite. MRI was performed at 25°C using a 1.5 T clinical system to determine the T1 relaxation times and subsequently, the T1 relaxivity. Results: The size of the nanocomposite was in the range of 80-200 nm. The nanocomposite without DOX loading (Gd3+/13X/FA) showed compatibility for A549 cells for all concentrations while DOX-loaded nanocomposite was toxic for 62% of the cells at the concentration of 0.4 mg/ml. The T1 relaxivity of Gd3+/13X/FA/DOX nanocomposite was 4.0401 mM-1s-1. Conclusion: Gd3+/13X/FA/DOX nanocomposite shows a T1 relaxivity similar to the conventional gadolinium chelates, and a successful DOX loading.

scholarly journals Cutoff points of T1 rho / T2 mapping relaxation times distinguishing early-stage and advanced osteoarthritis

2021 ◽  
Author(s):  
Zhijian Yang ◽  
Chao Xie ◽  
Songwen Ou ◽  
Minning Zhao ◽  
Zhaowei Lin
Keyword(s):  
Early Stage ◽  
T2 Mapping ◽  
Relaxation Times ◽  
Cartilage Degeneration ◽  
Cutoff Point ◽  
Grading System ◽  
Total Knee Replacements ◽  
Bootstrap Simulation ◽  
Magnetic Resonance Imaging Mri ◽  
T1 Rho

IntroductionThe histopathology grading system is the gold post-operative method to evaluate cartilage degeneration in knee osteoarthritis (OA). Magnetic resonance imaging (MRI) T1 rho/T2 mapping imaging can be used as a preoperative detection. An association between histopathology and T1 rho/T2 mapping relaxation times value was suggested in previous research. However, the cutoff point was not determined among different histopathology grades. Our study was to discuss the cutoff point of T1 rho/T2 mapping.Material and methodsT1 rho/T2 mapping images were acquired from 80 samples before total knee replacements. Then the histopathology grading system was applied.ResultsThe mean T1 rho/T2 mapping relaxation times of 80 samples were 39.17 ms and 37.98 ms respectively. Significant differences were found in T1 rho/T2 mapping values between early-stage and advanced OA (P < 0.001). The cutoff point for T1 rho was at 33 ms with a sensitivity of 94.12 (95%CI: 80.3 to 99.3) and a specificity of 91.30 (95%CI: 79.2 to 97.6). The cutoff point for T2 mapping was suggested at 35.04 ms with a sensitivity of 88.24 (95%CI: 72.5 to 96.7) and specificity of 97.83 (95%CI: 88.5 to 99.9). After bootstrap simulation, 95% CI of T1 rho/T2 mapping cutoff point was estimated as 29.36 to 36.32 ms and 34.8 to 35.04 ms respectively. The area under PR curve of T1 rho/T2 mapping was 0.972 (95%CI: 0.925 to 0.992) and 0.949 (95%CI: 0.877 to 0.989) respectively.ConclusionsThe cutoff point of T1 rho relaxation times, which was suggested as 33 ms could be used to distinguish early-stage and advanced OA.

scholarly journals MCF-7, ACHN, and A549 Cancer Cells Characterized by Quantitative Magnetic Resonance Imaging In Vitro

2021 ◽  
Vol 12 (4) ◽  
pp. 5174-5186
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Cancer Cells ◽  
Relaxation Times ◽  
Resonance Imaging ◽  
T1 And T2 ◽  
Magnetic Resonance Imaging Mri ◽  
Mcf 7

To work with cancer cell cultures in vitro at 1.5 Tesla Magnetic Resonance Imaging (MRI), it was necessary to develop dedicated receiver coils. This device allowed to adjust the shape of the tested objects and thus improve the quality of imaging. One of the conditions for this new device was to increase the recorded signal level and reduce the distance between the tested object and the receiving elements of the coil. MCF7 (breast adenocarcinoma, Her-2 positive), ACHN (kidney cancer cells), and A549 (lung cancer cells) were characterized by using magnetic resonance imaging (MRI) in vitro. MRI measurements were performed using the clinical scanner with a 1.5 Tesla magnetic field. MCF-7, ACHN, and A549 cancer cells were characterized by T1 and T2 relaxation times. For MCF-7 cells, the relaxation times T1 and T2 were 2360 ± 12 ms and 116 ± 0.9 ms, respectively. For ACHN cells, the relaxation times T1 and T2 were 1354 ± 193 ms and 80 ± 9 ms, respectively. Values of T1 and T2 for A549 cancer cells cultures were 1527 ± 59 ms and 150 ± 8 ms, respectively. Once an accurate pulse protocol has been established and satisfactory reproducibility was obtained, the determination of relaxation times can be used as a tool to monitor cancer cell cultures using MRI in vitro based on the determination of changes in relaxation times.

T2 Mapping as a New Method for Quantitative Assessment of Cartilage Damage in Rheumatoid Arthritis

2019 ◽  
Vol 47 (6) ◽  
pp. 820-825 ◽  
Author(s):  
Nina Renner ◽  
Arnd Kleyer ◽  
Gerhard Krönke ◽  
David Simon ◽  
Stefan Söllner ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Articular Cartilage ◽  
Disease Activity ◽  
Disease Duration ◽  
T2 Mapping ◽  
Cartilage Damage ◽  
Relaxation Times ◽  
T2 Relaxation ◽  
Hand Joints ◽  
Magnetic Resonance Imaging Mri

Objective.Rheumatoid arthritis (RA) is associated with damage of the articular cartilage and the periarticular bone. While imaging of bone damage has substantially improved in recent years, direct imaging of the articular cartilage of the hand joints in patients with RA is still challenging. The study used T2 mapping of the finger joints to assess cartilage damage in RA.Methods.Magnetic resonance imaging (MRI) at 3 Tesla was done in 30 patients with RA, and T2 relaxation times visualizing alteration in the collagen network and hydration of articular cartilage were mapped in 6 cartilage regions of the metacarpophalangeal (MCP) joints 2 and 3. Values were related to autoantibody status [anticitrullinated protein antibodies (ACPA), rheumatoid factor (RF)], disease duration, and disease activity as well as sex and age of the patients.Results.T2 relaxation times could be reliably measured in the 6 regions of the MCP joints. Significantly higher relaxation times indicating more advanced cartilage alterations were observed in the metacarpal heads of ACPA-positive (p = 0.001–0.010) and RF-positive patients (p = 0.013–0.025) as well as those with longer disease duration (> 3 yrs; p = 0.028–0.043). Current disease activity, sex, and age did not influence T2 relaxation times.Conclusion.These data show that cartilage damage can be localized and quantified in the hand joints of patients with RA by T2 mapping. Further, ACPA and RF positivity as well as disease duration appear to be the crucial factors influencing cartilage damage.

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