Ultrafast imaging of vascular tissue ablation by an XeCl excimer laser

摘要

Ablation and tissue removal of normal and atherosclerotic arterial wall by pulses of $lambda = 308 nm laser radiation have been probed by visible pulsed dye laser radiation. Photographs have been taken where the samples are irradiated in saline solution. The pulsewidth of the ablating XeCl excimer laser is about $TOP@r = 30 ns FWHM. The pulses have been transmitted through a fused silica fiber with a core diameter of 600 $mu@m. The pulse energy was set to 20 mJ at the distal end of the fiber corresponding to a fluence of 7.5 J/cm$+2$/, which is well above the ablation threshold. Visible radiation of a dye laser operated at a wavelength of $lambda = 580 nm ($TOP@r approximately 10 ns FWHM) is used to illuminate the tissue surface and the ablation plume. The delay time of the probing pulses with respect to the 308 nm pulses is varied in the nanosecond range up to several hundred microseconds. The ablation process and the resulting plume above the tissue surface are recorded with a CCD camera attached to a PC-based image-processing system. All samples under investigation were fresh human cadaver aortic and femoral artery specimens ($LSEQ@48 h), which had been shock-frozen. The arterial segments showed different types of lipid rich and calcified plaques.