Investigation of random lasing as a feedback mechanism for tissue differentiation during laser surgery

Abstract

Laser surgery provides clean, fast and accurate cutting of tissue. However, it is difficult to detect what kind of tissue is being cut. Therefore, a wrong cut may lead to iatrogenic damage of structures. A feedback system should automatically stop the cutting process when a nerve is reached or accidentally being cut to prevent its damage. This could increase the applicability and safety of using a laser scalpel in surgical procedures. In this study, random lasing (RL) is used to differentiate between skin, fat, muscle and nerve tissue. Among these tissue types, a special emphasis is made on the differentiation of nerve from the rest of the tissues, especially fat since nerve is covered by a fatty layer. The differentiation is done for ex-vivo tissues of a pig animal model. The results show that random lasing can be used to differentiate these tissue types also under room light conditions in open air.

Combined Nd:YAG and Er:YAG lasers for real-time closed-loop tissue-specific laser osteotomy

“…However, in our method, the laser energy applied (4.10 mJ) is much lower than that used for LIBS (38 mJ for ns-Excimer laser [32,33], 73-108 mJ for ns-Nd:YAG laser [31,[34][35][36][37][38], and 75-200 mJ for CO 2 -LIBS [41]) or shockwave measurements (200 mJ for ns-Nd:YAG [27,28], and 0.75-15 J for ms-fiber laser [29]). Also, the energy applied is well below the reported energy required to pump the tissue for random lasing (100 mJ for ns-Nd:YAG [30]), and pyrolysis analysis (300-2000 mJ for µs-Er:YAG [43,44]), which occurs inside the ablation zone in the laser-tissue interaction map. Differentiating tissue using a low energy (non-ablating) laser beam has two main advantages.…”

“…In order to preserve the adjacent soft tissue, several approaches to such differentiation have been developed using the optical properties of the ablated tissues. These methods include optical coherence tomography (OCT) [12,13], Raman spectroscopy [14][15][16][17], autofluorescence spectroscopy [18,19], diffuse reflectance spectroscopy (DRS) [20][21][22][23], ablative optoacoustic techniques [24][25][26][27][28][29], random lasing [30], laser-induced breakdown spectroscopy (LIBS) [31][32][33][34][35][36][37][38][39][40][41][42], and combustion/pyrolysis light analysis [43,44]. However, many of these methods have not been tested in combination with an ablating laser; studies have focused on tissue differentiation only.…”

Biophotonic probes for bio-detection and imaging

“…Random lasing has been demonstrated in different kinds of tissues stained with various fluorescent dyes, including bovine heart and bone 52 , 93 , rat muscle and brain 94 , 95 , human colon, kidney and cancerous tissue 92 , 96 , 97 . Since the output characteristics of random lasing are closely coupled with the structure and microenvironment of the tissues, lasing spectra can be used as a useful tool to distinguish malignant from healthy tissues 98 , to probe subtle structural alterations 52 , and to sense biological changes 99 . Random lasing provides relatively convenient methods to generate tissue lasers without need to introduce any external cavities.…”

Advances in random lasing sensing

“…The pumping system is often provided by a laser beam. Random lasing has been observed in biological material [17][18][19][20][21][22][23] and differences between healthy and cancerous human tissue has also been reported. [24][25][26][27][28] Developing a sensor based on random lasing 29-32 is of great interest, since random laser has an emission "fed" the feedback due to the scattering, making such a system a natural candidate for studying materials with strong disorder.…”