Photothermal effect of infrared lasers on ex vivo lamb brain tissues

Özgürün, Baturay; Gülsoy, Murat

doi:10.1117/12.2295906

Cited by 3 publications

(2 citation statements)

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“…Tissue dehydration tends to be a prominent factor in most laser tissue interaction studies where a hydrolytic laser is used [12,13,124,125]. It was also believed to be a prominent factor here.…”

Section: The Effect Of Biological Factors On the Seal Ratementioning

confidence: 95%

“…Most surgical laser systems in development today are intended for the purposes of ablation, less so coagulation. In fact, in many laser tissue interaction studies, coagulation as a by-product of ablation is considered a hinderance to the overall performance of the laser where ablation efficiency is inversely proportional to collateral thermal damage [10][11][12][13].…”

Section: Potential Benefits Of Laser-based Hemostasismentioning

confidence: 99%

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Optical Coherence Tomography for the Evaluation of Energy Seals and the Subsequent Evaluation of the Thulium Laser as a Hemostatic Instrument

Marques¹

2021

Preprint

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This thesis presents the development of a system which integrates both an Optical Coherence Tomography system and a high-powered Thulium fiber laser. The system was developed in order to study the interaction between Thulium laser and tissue via Optical Coherence Tomography feedback. This was done given the Thulium laser’s theoretical potential to serve as a multipurpose surgical instrument. The core work of the thesis is divided into two sections: <div>1. The development of an energy seal evaluation methodology using Optical Coherence Tomography. One-hundred and four avian embryonic vessels were subjected to Thulium laser irradiation at 1942 nm and subsequently imaged. Using both structural and Doppler feedback, several biomarkers were identified and used to classify irradiation outcomes as sealed or not sealed. The methodology developed here was compared to visual methodologies. It was found that the reported seal rate was dependent on the classification methodology (p = 0.01) where visual evaluation reported 18% more seals across the entire data set. The specificity of visual evaluation was dependent on the type of non-seal classification (p < 0.0001). Given that the developed methodology relied on the identification of biomarkers rather than user opinion, an objective evaluation methodology was achieved. Hemostatic systems evaluated visually should be re-evaluated. </div><div>2. Evaluating the Thulium laser as a hemostatic instrument. Average power, exposure time, and spot size were varied to maximize the seal rate. At sub 2 s exposure times the overall seal rate across all vessels was 29%. The highest seal rate achieved for a single condition was 60%. The rupture rate showed some correlation to average power.<div>Biological factors were found to have a significant effect on the seal rate where the mean vessel diameter for non-seal outcomes was greater than that for seal outcomes </div><div>(p < 0.001). Tissue dehydration was a factor in this study. The average heat affected zone was 2.2 ± 1.1 mm, typical of a hydrolytic laser. This finding affirmed that hydrolytic lasers can induce seals despite the dimensions of the optical zone. As irradiance increased so did the heat affected zone, the opposite was true for exposure time. Using a dose until seal approach the seal rate was 95% across 18 vessels. The average therapeutic time was 9 ± 3 s for single vessel. Based on the overall lack of predictability observed in interactions between Thulium laser and vascular tissue, as well as the relatively poor seal rates, the Thulium laser was not recommended to be used in hemostatic applications. </div></div>

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Section: The Effect Of Biological Factors On the Seal Ratementioning

confidence: 95%

Section: Potential Benefits Of Laser-based Hemostasismentioning

confidence: 99%

Optical Coherence Tomography for the Evaluation of Energy Seals and the Subsequent Evaluation of the Thulium Laser as a Hemostatic Instrument

Marques¹

2021

Preprint

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Pulsed thulium laser blood vessel haemostasis as an alternative to bipolar forceps during neurosurgical tumour resection

et al. 2023

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Due to wavelength-specific water absorption, infrared lasers like the thulium laser emitting at 1940 nm wavelength proved to be suitable for coagulation in neurosurgery. Commonly bipolar forceps used for intraoperative haemostasis can cause mechanical and thermal tissue damage, whilst thulium laser can provide a tissue-gentle haemostasis through non-contact coagulation. The aim of this work is a less-damaging blood vessel coagulation by pulsed thulium laser radiation in comparison to standard bipolar forceps haemostasis. Ex vivo porcine blood vessels in brain tissue (0.34 ± 0.20 mm diameter) were irradiated in non-contact with a thulium laser in pulsed mode (1940 nm wavelength, 15 W power, 100–500 ms pulse duration), with a CO2 gas flow provided simultaneously at the distal fibre tip (5 L/min). In comparison, a bipolar forceps was used at various power levels (20–60 W). Tissue coagulation and ablation were evaluated by white light images and vessel occlusion was visualised by optical coherence tomography (OCT) B-scans at a wavelength of 1060 nm. Coagulation efficiency was calculated by means of the quotient of the difference between the coagulation and ablation radius to the coagulation radius. Pulsed laser application achieved blood vessel occlusion rate of 92% at low pulse duration of 200 ms with no occurrence of ablation (coagulation efficiency 100%). Bipolar forceps showed an occlusion rate of 100%, however resulted in tissue ablation. Tissue ablation depth with laser application is limited to 40 μm and by a factor of 10 less traumatising than with bipolar forceps. Pulsed thulium laser radiation achieved blood vessel haemostasis up to 0.3 mm in diameter without tissue ablation and has proven to be a tissue-gentle method compared to bipolar forceps.

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