Mapping immune cell infiltration using restricted diffusion MRI

• Published in: Magnetic resonance in medicine Vol. 77; no. 2; pp. 603 - 612
• Main Authors: Yeh, Fang‐Cheng, Liu, Li, Hitchens, T. Kevin, Wu, Yijen L.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.02.2017
• Subjects: Animals; apparent diffusion coefficient (ADC); Cell density; Cell Tracking - methods; Correlation analysis; Correlation coefficients; Density; Diffusion; Diffusion Magnetic Resonance Imaging - instrumentation; Diffusion Magnetic Resonance Imaging - methods; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; immune cell infiltration; Immune system; Infiltration; Inflammation; Ischemia; ischemia‐reperfusion injury; Macrophages; Macrophages - immunology; Macrophages - pathology; Magnetic resonance imaging; Male; Mathematical analysis; Myocardial Reperfusion Injury - diagnostic imaging; Myocardial Reperfusion Injury - immunology; Myocardial Reperfusion Injury - pathology; Myocardium; Neutrophil Infiltration - immunology; Phantoms, Imaging; Rats; Reperfusion; Reproducibility of Results; restricted diffusion; restricted diffusion imaging (RDI); Sensitivity and Specificity; Tensors; ischemia-reperfusion injury; apparent diffusion coefficient (ADC); restricted diffusion imaging (RDI); immune cell infiltration; restricted diffusion
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.26143

Purpose Diffusion MRI provides a noninvasive way to assess tissue microstructure. Based on diffusion MRI, we propose a model‐free method called restricted diffusion imaging (RDI) to quantify restricted diffusion and correlate it with cellularity. Theory and Methods An analytical relation between q‐space signals and the density of restricted spins was derived to quantify restricted diffusion. A phantom study was conducted to investigate the performance of RDI, and RDI was applied to an animal study to assess immune cell infiltration in myocardial tissues with ischemia‐reperfusion injury. Results Our phantom study showed a correlation coefficient of 0.998 between cell density and the restricted diffusion quantified by RDI. The animal study also showed that the high‐value regions in RDI matched well with the macrophage infiltration areas in the H&E stained slides. In comparison with diffusion tensor imaging (DTI), RDI exhibited its outperformance to detect macrophage infiltration and delineate inflammatory myocardium. Conclusion RDI can be used to reveal cell density and detect immune cell infiltration. RDI exhibits better specificity than the diffusivity measurement derived from DTI. Magn Reson Med 77:603–612, 2017. © 2016 International Society for Magnetic Resonance in Medicine