Validation of diffusion and exchange imaging biomarkers via simultaneous real-time NMR and optical microscopy.

Diffusion MRI can reflect features of tissue microstructure and homeostasis, but direct validation in living neural tissue remains challenging. Here we combine optical microscopy and NMR for real-time recording on viable ex vivo neural tissue during environmental perturbations. Simultaneous high-temporal-resolution NMR and optical microscopy are used to monitor apparent diffusion coefficient (ADC), apparent exchange rate (AXR), intrinsic optical signal (IOS), and intracellular calcium in ex vivo neonatal mouse spinal cord during osmotic and ionic perturbations. We find that ADC correlates strongly with IOS, while AXR decreases with depolarization. ADC and AXR are sensitive to distinct features of cellular swelling, supporting their complementary roles in probing tissue viability and function.