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A noninvasive tumor oxygenation imaging strategy using magnetic resonance imaging of endogenous blood and tissue water.

ABSTRACT: To present a novel imaging strategy for noninvasive measurement of tumor oxygenation using MR imaging of endogenous blood and tissue water.The proposed approach for oxygen partial pressure (pO2) estimation is based on intravoxel incoherent motion diffusion MRI and the dependence of the blood R2 relaxation rate on the inter-echo spacing measured using a multiple spin-echo Carr-Purcell-Meiboom-Gill sequence and weak-field diffusion model. The accuracy of the approach was validated by comparison with (19)F MRI oximetry.The results in eight rats at 4.7 T showed that tumors have longer T1 (1980?±?186 ms) and T2 (59?±?9 ms) relaxation times, heterogeneous blood volume fraction (0.23?±?0.1), oxygen saturation level (Y) (0.53?±?0.12), and pO2 (36?±?15 mmHg) distributions compared with normal muscle (T1 1480?±?86 ms, T2 29?±?2 ms, blood volume fraction 0.22?±?0.03, Y 0.49?±?0.06, and pO2 39?±?5 mmHg). pO2 estimates based on the novel (1)H approach were essentially identical with (19)F observations.The study indicates that noninvasive measurement of tumor pO2 using (1)H MRI derived multiparametric maps is feasible and could become a valuable tool to evaluate tumor hypoxia.

SUBMITTER: Zhang Z

PROVIDER: S-EPMC3718873 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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A noninvasive tumor oxygenation imaging strategy using magnetic resonance imaging of endogenous blood and tissue water.

Zhang Zhongwei Z Hallac Rami R RR Peschke Peter P Mason Ralph P RP

Magnetic resonance in medicine 20140201 2

<h4>Purpose</h4>To present a novel imaging strategy for noninvasive measurement of tumor oxygenation using MR imaging of endogenous blood and tissue water.<h4>Theory and methods</h4>The proposed approach for oxygen partial pressure (pO2) estimation is based on intravoxel incoherent motion diffusion MRI and the dependence of the blood R2 relaxation rate on the inter-echo spacing measured using a multiple spin-echo Carr-Purcell-Meiboom-Gill sequence and weak-field diffusion model. The accuracy of ...[more]

PMID: 23447121

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Project description:BACKGROUND:The relationship between mean arterial pressure (MAP) and coronary blood flow is well described. There is autoregulation within a MAP range of 60 to 140 mmHg providing near constant coronary blood flow. Outside these limits flow becomes pressure-dependent. So far, response of myocardial oxygenation to changes in pressure and flow has been more difficult to assess. While established techniques mostly require invasive approaches, Oxygenation-Sensitive (OS) Cardiovascular Magnetic Resonance (CMR) is a technique that can non-invasively assess changes in myocardial tissue oxygenation. The purpose of this study was to follow myocardial oxygenation over a wide range of blood pressure variation within and outside known coronary autoregulatory limits using OS-CMR, and to relate these data to coronary hemodynamics. METHODS:Ten anaesthetized swine (German Large White) underwent left-sided thoracotomy and attachment of a perivascular flow probe to the proximal left anterior descending (LAD) coronary artery for continuous measurement of blood flow (QLAD). Thereafter, animals were transferred into a 3T MRI scanner. Mean arterial pressure (MAP) was varied in 10-15 mmHg steps by administering alpha1-receptor agents phenylephrine or urapidil. For each MAP level, OS-CMR images as well as arterial and coronary sinus blood gas samples were obtained simultaneously during brief periods of apnea. Relative changes (?) of coronary sinus oxygen saturation (ScsO2), oxygen delivery (DO2) and demand (MVO2), extraction ratio (O2ER) and excess (?) from respective reference levels at a MAP of 70 mmHg were determined and were compared to %change in OS-signal intensity (OS-SI) in simultaneously acquired OS-CMR images. RESULTS:QLAD response indicated autoregulation between MAP levels of 52 mmHg (lower limit) and127 mmHg (upper limit). OS-CMR revealed a global myocardial oxygenation deficit occurring below the lower autoregulation limit, with the nadir of OS-SI at -9.0%. With MAP values surpassing 70 mmHg, relative OS-SI increased to a maximum of +10.6%. Consistent with this, ?ScsO2, ?DO2, ?MVO2, ?O2ER and ?? responses indicated increasing mismatch of oxygenation balance outside the autoregulated zone. Changes in global OS-CMR were significantly correlated with all of these parameters (p?0.02) except with ?MVO2. CONCLUSION:OS-CMR offers a novel and non-invasive route to evaluate the effects of blood pressure variations, as well as of cardiovascular drugs and interventions, on global and regional myocardial oxygenation, as demonstrated in a porcine model. OS-CMR identified mismatch of O2 supply and demand below the lower limit of coronary autoregulation. Vasopressor induced acute hypertension did not compromise myocardial oxygenation in healthy hearts despite increased cardiac workload and O2 demand. The clinical usefulness of OS-CMR remains to be established.

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A noninvasive tumor oxygenation imaging strategy using magnetic resonance imaging of endogenous blood and tissue water.

Publications

A noninvasive tumor oxygenation imaging strategy using magnetic resonance imaging of endogenous blood and tissue water.

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