Improved photoacoustic dosimetry for retinal laser surgery

Suzie Dufour; Robert B. Brown; Pascal Gallant; Ozzy Mermut

doi:10.1117/12.2306888

19 February 2018 Improved photoacoustic dosimetry for retinal laser surgery

Suzie Dufour, Robert B. Brown, Pascal Gallant, Ozzy Mermut

Proceedings Volume 10474, Ophthalmic Technologies XXVIII; 104742I (2018) https://doi.org/10.1117/12.2306888
Event: SPIE BiOS, 2018, San Francisco, California, United States

Abstract

Lasers are employed for numerous medical interventions by exploiting ablative, disruptive or thermal effects. In ocular procedures, lasers have been used for decades to treat diseases such as diabetic retinopathy, macular edema and aged related macular degeneration via photocoagulation of retinal tissues. Although laser photocoagulation is well established in today’s practice, efforts to improve clinical outcomes by reducing the collateral damage from thermal diffusion is leading to novel treatments using shorter (μs) laser pulses (e.g. selective retinal therapy) which result in physical rather than thermal damage. However, for these new techniques to be widely utilized, a method is required to ensure safe but sufficient dosage has been applied, since no visible effects can be seen by ophthalmoscopy directly post treatment. Photoacoustic feedback presents an attractive solution, as the signal is dependent directly on absorbed dosage. Here, we present a method that takes advantage of temporal pulse formatting technology to minimize variation in absorbed dose in ophthalmic laser treatment and provide intelligent dosimetry feedback based on photoacoustic (PA) response. This method tailors the pulse to match the frequency response of the sample and/or detection chain. Depending on the system, this may include the absorbing particle size, the laser beam diameter, the laser pulse duration, tissue acoustic properties and the acoustic detector frequency response. A significant improvement (<7x) of photoacoustic signal-to-noise ratio over equivalent traditional pulse formats have been achieved, while spectral analysis of the detected signal provides indications of cavitation events and other sample properties.

Citation Download Citation

Suzie Dufour, Robert B. Brown, Pascal Gallant, and Ozzy Mermut "Improved photoacoustic dosimetry for retinal laser surgery", Proc. SPIE 10474, Ophthalmic Technologies XXVIII, 104742I (19 February 2018); https://doi.org/10.1117/12.2306888

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