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

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 CO
2 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.