Selective laser vaporization of polypropylene mesh in tissue

Customer case

University of North Carolina at Charlotte is a public research university founded in 1946. Department of Physics and Optical Science is dedicated on developing minimally invasive optics solutions for biomedical indications, such as tissue ablation, nerve simulation and surgical applications. Collaborations with Carolinas Medical Center at Charlotte and John Hopkins University at Maryland. Most recent research activities have focused on development of thulium fiber laser (TFL) as an alternative to the gold standard Holmium: YAG laser for lithotripsy (destruction of kidney stones), and machine learning to optically track kidney stones.

Prof. Nathaniel M. Fried

Modulight products: ML7000 series laser at 647 nm (See ML7710 for corresponding product info)

Laser use: Selective laser vaporization of vaginal mesh after erosion and noninvasive creation of subsurface thermal lesions for urological purposes (laser vasectomy or treatment of female stress urinary incontinence) while preserving tissue surface on a millimeter scale.

Link to the study:

 

Motivation for the study

Surgical mesh is used to treat female stress urinary incontinence (SUI) and transvaginal pelvic organ prolapse (POP). However, erosion of this synthetic, non-absorbable mesh is a common complication and in more than half of these cases, a surgical excision of the mesh in the operating room is required. The mesh removal is technically challenging, may damage healthy adjacent tissues, and in some cases must be repeated several times. This study aims to explore the feasibility of selective laser vaporization, which could provide safer and improved method for mesh removal. This method is based on selective photothermolysis where target is destroyed through preferential absorption of pulsed laser radiation.

 

Laser vaporization setup

A compact 7 Watt Modulight laser device at 647 nm was selected for irradiation because absorption by water, hemoglobin, and other tissue chromophores is low at this wavelength while polypropylene absorption is high. This allows for selective laser targeting and vaporization of the mesh. A silica fiber optic patch-cord was used to deliver the laser irradiation from the laser to a lens collimating system, which provided 0.95 µm-diameter laser spot on the surface of sample. A single laser pulse of 100 ms duration was delivered to the tissue, suture, and mesh in the experiments. A camera is included for magnification and alignment of the laser beam with the target, while a separate thermal camera records the temperature of the laser-irradiated target during the testing.

Results

Both suture and mesh were successfully vaporized at the point of irradiation with a single laser pulse. Peak temperature was 180 ⁰C for suture and 232 ⁰C for mesh during the irradiation. Both temperatures are well above the melting temperature of 160-170 ⁰C for these materials. In contrast, temperature of tissue increased only by 1 ⁰C due to low absorption of this wavelength by tissue chromophores.

 

 

 

 

Photo and graph from the original publication, reproduced with permission from the contact author of the publication.

 

 

Conclusions:
Selective vaporization of polypropylene suture/mesh was successful using clinical diode laser system at 647 nm wavelength. There was no significant thermal elevation in the irradiated tissue, indicating that misalignment of the laser during a clinical procedure would not be hazardous to the patient. Further development of this technique is warranted in an in vivo animal model prior clinical application. Procedure could also be automated in future by incorporating a scanning system into the fiber optic probe or a handpiece to rapidly scan the laser spot across the entire mesh for complete vaporization.

 

Related Modulight products and Services

 

Related Publications

Selective laser vaporization of polypropylene mesh used in treatment of female stress urinary incontinence and pelvic organ prolapse: preliminary studies using a red diode laser
David Burks, Sarah B. Rosenbury, Michael J. Kennelly, Nathaniel M. Fried
Lasers Surg Med, 2012, 44 (4)

 

 

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