Myocardial Tissue Oxygenation and Microvascular Blood Volume Measurement Using a Contrast Blood Oxygenation...

Area of Science:

• Cardiovascular Imaging
• Biomedical Engineering
• Physiology

Background:

• Assessing drug-induced changes in microvascular blood volume (MBV) and tissue oxygenation is crucial for understanding cardiovascular function and disease.
• Current methods often rely on invasive techniques or contrast agents, limiting their clinical applicability.
• Calibrated blood oxygen level-dependent (BOLD) MRI offers a non-invasive approach to quantify these physiological parameters.

Purpose of the Study:

• To develop and validate a quantitative method using calibrated BOLD MRI to measure drug-induced changes in MBV and oxygenation.
• To investigate the differential effects of vasoactive drugs (adenosine and dobutamine) on myocardial microvasculature and oxygenation.
• To establish the feasibility of this MRI technique for assessing microvascular function in a preclinical model.

Main Methods:

• Employed calibrated BOLD MRI to acquire R2* relaxation rate maps in 12 healthy rats.
• Administered adenosine to increase blood flow and dobutamine to increase oxygen consumption, with and without an iron oxide nanoparticle contrast agent.
• Acquired R2* maps under various drug and contrast conditions to quantify MBV and oxygenation.

Main Results:

• Adenosine increased total MBV by 10.8%, while dobutamine increased it by 25.6% (P < 0.05).
• Both drugs induced significant endocardial vs. epicardial differences in MBV and oxygenation changes (P < 0.05).
• Total myocardial oxygenation increased with adenosine (+6.59%) and dobutamine (+1.64%), though the latter was not statistically significant (P = 0.27).

Conclusions:

• Calibrated BOLD MRI can quantitatively measure drug-induced microvascular volume and oxygenation changes.
• Demonstrated distinct physiological responses to adenosine and dobutamine, highlighting the method's sensitivity.
• This non-invasive MRI approach holds significant clinical potential for evaluating microvascular diseases without radiopharmaceuticals or gadolinium contrast agents.