MRI-guided holmium:YAG interstitial laser phototherapy and cavitron ultrasonic aspiration in an ex-vivo model: a comparison and dosimetry study of laser/ultrasonic tissue interactions

摘要

Abstract: study a model was developed to quantify levels of laser/cavitron energy deposition and to correlate this with MRI and histological damage. The Ho:YAG laser (2.1 micron wavelength) and cavitron were used on separate matching tissues, with exposure to succeedingly higher energy densities by an accurate and reproducible method of dosimetry. Post laser/cavitron treatments were then evaluated using the Signa 1.5 T MRI (GE Medical Systems). In this study, fast gradient echo (rapid SPGR) pulse sequence was used to visualize and quantify signal changes. Thereafter, biopsies were taken for standard H&E preparation and quantification of laser or cavitron damage. FSE and turbo flash images taken demonstrated a linear correlation between energy deposition in the tissue and signal intensity changes for the laser or signal void for the cavitron. These signal changes correlated well with the histological measurements of the same tissues. This initial study demonstrates the potential clinical feasibility of these two energy delivery systems on various tissues. Furthermore it suggests the need for future development of non-invasive quantitative techniques for real time MRI monitoring in the treatment of deep and difficult to reach tumors of the head and neck and other parts of the body. !10