Photoacoustic molecular imaging for in vivo liver iron quantitation

A recent study showed that ferritin is a suitable endogenous contrast agent for photoacoustic molecularimaging in cultured mammalian cells. We have therefore tested whether this imaging technique can be usedfor in vivo quantification of iron in mouse livers. To verify this hypothesis, we used multispectral optoacoustictomography (MSOT) to image albino CD1 mice before and after experimental iron loading. Postmortem assaysshowed that the iron treatment caused a 15-fold increase in liver iron and a 40-fold increase in liver ferritin levels,while in vivo longitudinal analysis using MSOT revealed just a 1.6-fold increase in the ferritin/iron photoacousticsignal in the same animals. We conclude that MSOT can monitor changes in ferritin/iron levels in vivo, but itssensitivity is much lower than that of ex vivo iron assays.