What is the Component That Appears in Diffusion-Weighted Imaging at Low B Values?

Kimihiro Ogisu¹, Hidetsugu Sakai², Toru Yamamoto²

The signal from intravoxel incoherent motion (IVIM) appears in diffusion-weighted imaging at low b values. This low-b-value component is believed to reflect capillary blood flow in tissue. However, the quantity of the low-b-value component contradicts the data on capillary blood volume in the literature. To determine the origin of the low-b-value component, we investigated the proton density and T2 value of the component. We found that the low-b-value component has a larger T2 value than does blood and that this component exhibits IVIM. Because the hydrostatic pressure and osmotic pressure in capillaries drive interstitial fluid flow, which has a large T2 value, we suggest that the interstitial fluid mainly contributes to the low-b-value component.