Figure 3. In-vivo femtosecond laser-induced microhaemorrhage formation.

(A) In-vivo two-photon excited fluorescence (2PEF) image frames showing rapid expansion of the microhaemorrhage after irradiation of a penetrating arteriole about 100 μm beneath the cortical surface with a single, 800 nm wavelength, 100 fs duration, roughly 1 μJ energy laser pulse. Laser energy is only absorbed in the focal volume, leading to damage to and rupture of the vessel wall, but with no direct laser damage to surrounding tissue, thus producing a model of cortical microhaemorrhage. Fluorescently labelled blood plasma is red. The blood plasma and red blood cells (seen as dark shadows in the sea of fluorescent plasma) are pushed into the brain parenchyma. Neurons and astrocytes are labelled green with Oregon green BAPTA. (B) In-vivo 2PEF image stacks of fluorescently labelled blood plasma spanning a 20 μm depth centred at the microhaemorrhage origin in warfarin-treated animals and controls. Extravasated plasma is detected as diffuse fluorescence, in a halo surrounding the target vessel. The dark core immediately adjacent to the target vessel is filled with red blood cells. The warfarin-treated animal has a larger haematoma volume than the control. Image (A) reproduced from reference 46, by permission of OSA, the Optical Society.