Analysis of the Evaporation to Sublimation Phase Transition during Minimal Invasive Surgery Procedures via Pulsed CO2 lasers by Franco Canestri in BJSTR

Analysis of the Evaporation to Sublimation Phase Transition during Minimal Invasive Surgery Procedures via Pulsed CO2 lasers by Franco Canestri in BJSTR

Abstract

Objective

This Paper describes a mathematical approach to quantify the phase transition from ablation to evaporation of PMMA irradiated by pulsed CO₂ laser devices to be used as reference data for Ultra-Conservative Minimally Invasive Surgery (UCMIS) with commercially available medical lasers. This step is important because it allows forecasting the micro boundary drilling conditions of a laser device implemented in Operating Room (OR) in conjunction to minimally invasive tools. The primary goals of reducing the invasive characters of an operation, and the associated risks of unwanted lateral tissue damage during surgery, are the key objectives of UCMIS protocols.

Background Data

Currently, the data available on literature do not report any guideline for a generic set-up configuration which produces the smallest ablations using non-Gaussian laser beams. This would help to further improve the overall quality of the UCMIS protocols via endoscopic scalpels to deliver minimal ablative energy. The Author has recently published a study on absolute UCMIS conditions.

Methods

The equation of the evaporation time has been used to identify the most effective and safest correlation amongst the following five magnitudes: output power W, focal length f, pulse width t_1b, beam TEM mode (M2 parameter) and the safest "not-to-exceed” radius of the allowed crater on the irradiated sample. The mathematical validation of this methodology is described and discussed.

Results

The optimized combination of these 5 magnitudes for a TEM₂₂ laser beam profile has been identified and it can be used for reference of UCMIS procedures using commercially available pulsed CO₂ lasers at the wavelength of 10.6 μm. The PMMA ablation temperature and the start of the evaporation phase can happen only starting from 354.5 degC or above. More investigations are needed to validate the whole procedure before any preliminary surgical utilization can be considered.

https://biomedres.us/pdfs/BJSTR.MS.ID.000493.pdf 

https://biomedres.us/fulltexts/BJSTR.MS.ID.000493.php