and T<sub>1</sub> assessment of abdominal tissue response to graded hypoxia and hypercapnia using a controlled gas mixing circuit for small animals

Ganesh, Tameshwar; Estrada, Marvin; Duffin, James; Cheng, Hai‐Ling Margaret

doi:10.1002/jmri.25169

Cited by 17 publications

(28 citation statements)

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“…For gbc16, the BOLD response mirrored that observed for gbc100 (Figure A): decreased blood oxygenation (increased R 2 *). A similar trend of BOLD response to hypoxic gas breathing was reported for normal abdominal organs, placenta, and the brain . Remarkably, for gbc16, T 1 w SI decreased in small SC tumors, but increased in larger SC tumors (Figures B and ), demonstrating a binary response associated with tumor volume.…”

Section: Discussionsupporting

confidence: 78%

“…The magnitude of R 2 * response for gbc16 was generally larger than that for gbc100 (Figures , , and ), although gbc16 made a relatively smaller change in the inspired oxygen fraction (f i O 2 ). This “asymmetrical” R 2 * response has also been reported for rat abdominal organs, mouse placenta and fetus . Due to the nonlinear (sigmoidal) shape of the oxygen‐hemoglobin dissociation curve, the change in local deoxyhemoglobin concentration ([dHb]) in the blood depends not only on the magnitude of change in f i O 2 but also on the local, baseline oxygenation state ( i.e ., the location on the dissociation curve).…”

Section: Discussionmentioning

confidence: 54%

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Oxygen‐sensitive MRI assessment of tumor response to hypoxic gas breathing challenge

et al. 2019

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Oxygen‐sensitive MRI has been extensively used to investigate tumor oxygenation based on the response (R2* and/or R1) to a gas breathing challenge. Most studies have reported response to hyperoxic gas indicating potential biomarkers of hypoxia. Few studies have examined hypoxic gas breathing and we have now evaluated acute dynamic changes in rat breast tumors. Rats bearing syngeneic subcutaneous (n = 15) or orthotopic (n = 7) 13762NF breast tumors were exposed to a 16% O2 gas breathing challenge and monitored using blood oxygen level dependent (BOLD) R2* and tissue oxygen level dependent (TOLD) T1‐weighted measurements at 4.7 T. As a control, we used a traditional hyperoxic gas breathing challenge with 100% O2 on a subset of the subcutaneous tumor bearing rats (n = 6). Tumor subregions identified as responsive on the basis of R2* dynamics coincided with the viable tumor area as judged by subsequent H&E staining. As expected, R2* decreased and T1‐weighted signal increased in response to 100% O2 breathing challenge. Meanwhile, 16% O2 breathing elicited an increase in R2*, but divergent response (increase or decrease) in T1‐weighted signal. The T1‐weighted signal increase may signify a dominating BOLD effect triggered by 16% O2 in the relatively more hypoxic tumors, whereby the influence of increased paramagnetic deoxyhemoglobin outweighs decreased pO2. The results emphasize the importance of combined BOLD and TOLD measurements for the correct interpretation of tumor oxygenation properties.

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Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 54%

Oxygen‐sensitive MRI assessment of tumor response to hypoxic gas breathing challenge

et al. 2019

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“…The results of responses to the gas challenge are in agreement with the findings in healthy rat models. 16,22 Hypercapnia increased portal vein blood velocity and decreased hepatic artery blood velocity, which, in healthy volunteers, reduced liver T * 2 due to higher deoxyhemoglobin levels associated with deoxygenated portal vein blood flow. Hyperoxia increased liver T * 2 due to the high liver blood content and hypervascularity and low baseline oxyhemoglobin level.…”

Section: Discussionmentioning

confidence: 99%

Using MRI to study the alterations in liver blood flow, perfusion, and oxygenation in response to physiological stress challenges: Meal, hyperoxia, and hypercapnia

Cox

Palaniyappan

Aithal

et al. 2018

Magnetic Resonance Imaging

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Background Noninvasive assessment of dynamic changes in liver blood flow, perfusion, and oxygenation using MRI may allow detection of subtle hemodynamic alterations in cirrhosis. Purpose To assess the feasibility of measuring dynamic liver blood flow, perfusion, and T2* alterations in response to meal, hypercapnia, and hyperoxia challenges. Study Type Prospective. Subjects Ten healthy volunteers (HV) and 10 patients with compensated cirrhosis (CC). Field Strength/Sequence 3T; phase contrast, arterial spin labeling, and normalT2* mapping. Assessment Dynamic changes in portal vein and hepatic artery blood flow (using phase contrast MRI), liver perfusion (using arterial spin labeling), and blood oxygenation (normalT2* mapping) following a meal challenge (660 kcal), hyperoxia (target PETO2 of 500 mmHg), and hypercapnia (target increase PETCO2 of ∼6 mmHg). Statistical Tests Tests between baseline and each challenge were performed using a paired two‐tailed t‐test (parametric) or Wilcoxon‐signed‐ranks test (nonparametric). Repeatability and reproducibility were determined by the coefficient of variation (CoV). Results Portal vein velocity increased following the meal (70 ± 9%, P < 0.001) and hypercapnic (7 (5–11)%, P = 0.029) challenge, while hepatic artery flow decreased (–30 ± 18%, P = 0.005) following the meal challenge in HV. In CC patients, portal vein velocity increased (37 ± 13%, P = 0.012) without the decrease in hepatic artery flow following the meal. In both groups, the meal increased liver perfusion (HV: 82 ± 50%, P < 0.0001; CC: 27 (16–42)%, P = 0.011) with faster arrival time of blood (HV: –54 (–56‐30)%, P = 0.074; CC: –42 ± 32%, P = 0.005). In HVs, normalT2* increased after the meal and in response to hyperoxia, with a decrease in hypercapnia (6 ± 8% P = 0.052; 3 ± 5%, P = 0.075; –5 ± 6%, P = 0.073, respectively), but no change in CC patients. Baseline between‐session CoV <15% for blood flow and <10% for normalT2* measures. Data Conclusion Dynamic changes in liver perfusion, blood flow, and oxygenation following a meal, hyperoxic, and hypercapnic challenges can be measured using noninvasive MRI and potentially be used to stratify patients with cirrhosis. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1577–1586.

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“…(3) by taking the quotient rule on the left hand side and the product rule on the right hand side. For practical purposes, we can assume T 10 is constant with time, as the longitudinal relaxation of tissue with undoped blood changes minimally with blood volume fluctuations 10 . Since both C b and v b are time-dependent, the result is:…”

Section: Theorymentioning

confidence: 99%

A novel MRI analysis for assessment of microvascular vasomodulation in low-perfusion skeletal muscle

Zakher

Ganesh

Cheng

2020

Sci Rep

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Compromised microvascular reactivity underlies many conditions and injuries, but its assessment remains difficult, particularly in low perfusion tissues. In this paper, we develop a new mathematical model for the assessment of vasomodulation in low perfusion settings. A first-order model was developed to approximate changes in T 1 relaxation times as a result of vasomodulation. Healthy adult rats (N = 6) were imaged on a 3-Tesla clinical MRI scanner, and vasoactive response was probed on gadofosveset using hypercapnic gases at 20% and 5% CO 2 to induce vasoconstriction and vasodilation, respectively. MRI included dynamic 3D T 1 mapping and T 1-weighted images during gas challenge; heart rate was continuously monitored. Laser Doppler perfusion measurements were performed to corroborate MRI findings. The model was able to identify hypercapnia-mediated vasoconstriction and vasodilation through the partial derivative T t ∂ ∂ 1. MRI on animals revealed gradual vasoconstriction in the skeletal muscle bed in response to 20% CO 2 followed by gradual vasodilation on transitioning to 5% co 2. These trends were confirmed on laser Doppler perfusion measurements. Our new mathematical model has the potential for detecting microvascular dysfunction that manifests in the early stages across multiple metabolic and ischemic pathologies.

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and T₁ assessment of abdominal tissue response to graded hypoxia and hypercapnia using a controlled gas mixing circuit for small animals

Cited by 17 publications

References 50 publications

Oxygen‐sensitive MRI assessment of tumor response to hypoxic gas breathing challenge

Oxygen‐sensitive MRI assessment of tumor response to hypoxic gas breathing challenge

Using MRI to study the alterations in liver blood flow, perfusion, and oxygenation in response to physiological stress challenges: Meal, hyperoxia, and hypercapnia

A novel MRI analysis for assessment of microvascular vasomodulation in low-perfusion skeletal muscle

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and T1 assessment of abdominal tissue response to graded hypoxia and hypercapnia using a controlled gas mixing circuit for small animals

Cited by 17 publications

References 50 publications

Oxygen‐sensitive MRI assessment of tumor response to hypoxic gas breathing challenge

Oxygen‐sensitive MRI assessment of tumor response to hypoxic gas breathing challenge

Using MRI to study the alterations in liver blood flow, perfusion, and oxygenation in response to physiological stress challenges: Meal, hyperoxia, and hypercapnia

A novel MRI analysis for assessment of microvascular vasomodulation in low-perfusion skeletal muscle

Contact Info

Product

Resources

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and T₁ assessment of abdominal tissue response to graded hypoxia and hypercapnia using a controlled gas mixing circuit for small animals