Method and apparatus for noninvasive quantitative detection of fibrosis in normal and viable myocardium by MRI
Embodiments provide a noninvasive quantitative method for detecting extent and/or types of fibrosis in the heart. In embodiments, information pertaining to the extent and/or types of fibrosis may aid in the diagnosis of specific cardiac diseases and heart failure and/or may assist in determining suitable treatment options. Embodiments provide methods and apparatuses for determining the extent of fibrosis in viable and nonviable myocardium, which may then be correlated to heart disease and failure. Thus, in an embodiment, a method of screening individuals for the purpose of heart disease or heart failure prevention may be provided using the detection methodology described herein.
1. A method of distinguishing normal myocardium from viable myocardium with diffuse interstitial and/or replacement fibrosis in heart tissue, comprising:
selecting a sample comprising viable heart tissue;
obtaining, with a magnetic resonance imaging device, a plurality of measurements of T 1 relaxation time in blood and in an extracellular component of the heart tissue before contacting the sample with an extracellular contrast agent;
contacting the sample with the extracellular contrast agent;
obtaining, with the magnetic resonance imaging device, a plurality of measurements of T 1 relaxation time in blood and in the extracellular component of the sample, after contact with the extracellular contrast agent and wherein the extracellular contrast agent is at equilibrium between the blood and the extracellular component of the heart tissue;
converting the relaxation times (T 1 ) into relaxation rates with R 1 =1/T 1 ; and
linearly regressing each R 1 rate determined for the viable heart tissue against a R 1 rate determined for the blood;
quantifying a myocardial partition coefficient for the extracellular contrast agent in the viable heart tissue using the T 1 relaxation time measurements in blood and in the extracellular component of the heart tissue before and after contacting the sample with the extracellular contrast agent;
obtaining a blood hematocrit level;
calculating the extracellular volume in the tissue sample using the myocardial partition coefficient partition coefficient and the blood hematocrit level; and
determining an extracellular volume fraction of the contrast agent to distinguish normal myocardium from viable myocardium with diffuse interstitial and/or replacement fibrosis.
2. The method of claim 1 , wherein contacting the sample with the extracellular contrast agent comprises contacting the sample with a Gadolinium-containing contrast agent.
3. The method of claim 1 , wherein contacting the sample with the extracellular contrast agent comprises contacting the sample with gadodiamide.
4. The method of claim 1 , wherein contacting the sample with the extracellular contrast agent comprises contacting the sample in-vivo with the extracellular contrast agent.
5. The method of claim 1 , wherein contacting the sample with the extracellular contrast agent comprises contacting the sample in-vitro with the extracellular contrast agent.
6. The method of claim 1 , further comprising determining a global diffuse fibrosis burden in the sample.
7. The method of claim 1 , further comprising classifying an extent of diffuse fibrosis in a patient from which the sample is selected to determine risk of heart failure or heart disease.
8. The method of claim 1 , further comprising determining and distinguishing between an extent of interstitial and an extent of replacement fibrosis in the sample.
9. The method of claim 1 , further comprising obtaining one or more images of the sample using computed x-ray tomography.
10. The method of claim 1 , further comprising determining the presence of, location of, and/or extent of interstitial and replacement fibrosis in a tissue sample or whole heart and correlating the determination with a heart condition, disease, or associated risk of a particular heart disease or failure.
11. The method of claim 10 , wherein correlating the determination with a heart condition, disease, or associated risk of a particular heart disease or failure is represented as a numeric or textual risk factor.