Theory of the BOLD effect in the capillary region: An analytical approach for the determination of T2/* in the capillary network of myocardium

Abstract

This article presents an analytical approach for the quantification of the blood oxygen level dependent (BOLD) effect in the capillary region. The capillary geometry of myocardium is considered. The relaxation rate R2/* is determined as a function of the capillary radius R(c), the intracapillary volume fraction RBV, and the diffusion coefficient D. When the intracapillary volume fraction is small, the approximation R2/* = RBV · τ-1 · (√1 + (τδω)2 - 1) is valid, with the correlation time τ = (R(c)/2/4D). (|ln RBV|/(1 - RBV)). The predictions of this model agree well with numerical simulations and experimental data of others and with data recently measured by our group.