Laser induced surface acoustic wave combined with phase sensitive optical coherence tomography for superficial tissue characterization: a solution for practical application.

Chunhui Li,Fan Zhang,Guangying Guan,Ruikang K Wang,Ghulam Nabi,Zhihong Huang

doi:10.1364/boe.5.001403

Abstract

Mechanical properties are important parameters that can be used to assess the physiologic conditions of biologic tissue. Measurements and mapping of tissue mechanical properties can aid in the diagnosis, characterisation and treatment of diseases. As a non-invasive, non-destructive and non-contact method, laser induced surface acoustic waves (SAWs) have potential to accurately characterise tissue elastic properties. However, challenge still exists when the laser is directly applied to the tissue because of potential heat generation due to laser energy deposition. This paper focuses on the thermal effect of the laser induced SAW on the tissue target and provides an alternate solution to facilitate its application in clinic environment. The solution proposed is to apply a thin agar membrane as surface shield to protect the tissue. Transient thermal analysis is developed and verified by experiments to study the effects of the high energy Nd:YAG laser pulse on the surface shield. The approach is then verified by measuring the mechanical property of skin in a Thiel mouse model. The results demonstrate a useful step toward the practical application of laser induced SAW method for measuring real elasticity of normal and diseased tissues in dermatology and other surface epithelia.

Highlights

The majority of pathological changes in the surface of organs such as skin results in the change of elastic properties and/or thickness of the affected layers
Discussions and conclusions In this paper we have presented a novel solution using laser induced surface acoustic waves (SAWs) to analyze the elasticity of soft tissues
A purpose-built black agar membrane can be applied on tissues in order to shield the heat generated by the high energy laser pulse

Summary

Introduction

The majority of pathological changes in the surface of organs such as skin results in the change of elastic properties and/or thickness of the affected layers. Stage I skin cancer affects the epidermis and upper dermis layer, while stage II skin cancer involves the whole dermis layer and possibly the upper subcutaneous fat layer. These conditions would lead to the increase of epidermis and dermis layer thicknesses [4,5,6,7]. In case of gastrointestinal and urothelial cancers in urology, depth of cancer remains important information necessary for clinical decision making. To accurately carry this out the clinician requires years of extensive training and experience. A non-intrusive, non-invasive elastography method that can accurately measure mechanical properties in vivo is required

Methods

Results

Conclusion