Methods for in vivo evaluation of physiological conditions and/or organ or system function including methods to evaluate cardiopulmonary disorders such as chronic heart failure using polarized 129 Xe
In certain embodiments, methods of the present invention obtain NMR spectroscopy signal data that corresponds to the behavior of the polarized 129 Xe at a selected site(s) in selected environments in vivo. The gas exchange signal data can be used to evaluate: (a) the thickness of a barrier, such as a membrane, lining, wall or width of a lumen; (b) the operational condition or function of a membrane, body system or portion thereof; (c) cerebral perfusion; and/or (c) the efficacy of a therapeutic treatment used to treat a diagnosed disorder, disease, or condition. Thus, the present invention provides methods for screening and/or diagnosing a disorder or disease, and/or methods for monitoring the efficacy of therapeutics administered to subject to treat a disorder or disease.
1. An in vivo method for evaluating the blood brain barrier in a subject, comprising:
delivering polarized 129 Xe in vivo to a subject such that it diffuses into the blood stream and across the blood brain membrane to be taken up in tissue in the brain across the membrane, the polarized gas in the blood and brain tissue having distinct corresponding polarized gas NMR chemical shift signal frequencies;
destroying the polarization of the polarized 129 Xe in the brain tissue;
obtaining an NMR spectroscopic signal of the polarized gas in the subject over time at the brain tissue chemical shift frequency to generate at least one dynamic data set of the NMR spectroscopic signal strength values over time;
evaluating the dynamic data; and
assessing the blood brain barrier based on data provided by said obtaining and evaluating steps.
2. A method according to claim 1 , wherein the evaluating step evaluates the polarized gas transit behavior of the polarized gas, the gas transit time corresponds to the time it takes the polarized gas to travel across the membrane and then enter the brain tissue after said destroying step.
3. A method according to claim 2 , wherein the brain tissue is gray matter, and wherein the step of assessing includes determining the thickness of the blood brain barrier.
4. A method according to claim 1 , wherein the obtaining step is carried out to monitor the efficacy of a pharmaceutical agent administered to the subject to evaluate its impact on the thickness of the blood brain barrier.
5. A method according to claim 4 , wherein the obtaining step is carried out both before and after the administration of the agent to the subject.
6. A method according to claim 1 , wherein the step of evaluating comprises assessing perfusion and ventilated oxygen levels in gray and white matter brain tissue based on data provided by said obtaining step.