In vivo safety study using radiation at wavelengths and dosages relevant to intravascular imaging

Significance: Intravascular photoacoustic (IVPA) imaging can identify native lipid in atherosclerotic plaques in vivo. However, the large number of laser pulses required to produce 3D images is a safety concern that has not been fully addressed. Aim: We aim to evaluate if irradiation at wavelengths and dosages relevant to IVPA imaging causes target vessel damage. Approach: We irradiate the carotid artery of swine at one of several energy dosages using radiation at 1064 or 1720 nm and use histological evaluation by a pathologist to identify dose-dependent damage. Results: Media necrosis was the only dose-dependent form of injury. Damage was present at a cumulative fluence of 50 J / cm(2) when using 1720 nm light. Damage was more equivocally identified at 700 J / cm(2) using 1064 nm. Conclusions: In prior work, IVPA imaging of native lipid in swine has been successfully conducted below the damage thresholds identified. This indicates that it will be possible to use IVPA imaging in a clinical setting without damaging vessel tissue. Future work should determine if irradiation causes an increase in blood thrombogenicity and confirm whether damaged tissue will heal over longer time points.