Imaging laser induced thermal fields and effects

Rudolf M. Verdaasdonk*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

12 Citations (Scopus)
20 Downloads (Pure)


Laser light interaction with biological tissues is a combination of optical, thermal and mechanical effects depending on the energy applied per unit ofvolume per unit oftime. Visualization ofthe phenomena with a high temporal and spatial resolution, contributes to a better understanding of the mechanism of action, especially when pulsed lasers are involved. For this goal, setups were developed based on Schlieren techniques to image the interaction of pulsed (CO2, Holmium and Excimer) and CW (CO2, Nd:YAG, Cu-vapor) lasers with physiological media and biological tissues. In a 'fast' Schlieren setup, images of shock waves and fast expanding and imploding vapor bubbles were captured using very short light flashes (10 ns -10 is). These recordings suggest that these explosive vapor bubbles seem to be the main dynamism for tissue ablation. In a 'color' Schlieren setup, very small changes in optical density of the media induced by temperature gradients, were color coded. Calibration of the color images to absolute temperatures were performed by using calculated temperature distributions and by thermocouple measurements. Cameras with high speed shutters (0.1 - 50 ms) enabled the recording of dynamic images of the thermal relaxation and heat diffusion in tissues during variation of pulse length and repetition rate. Despite pulse lengths < ms, heat generation in tissue was considerable already at pulse repetition rates above a few Hz. Similar Schlieren techniques were applied to study the thermal characteristics of laser probes, e.g. for the treatment of Benign Prostatic Hyperplasia (BPH). In combination with thermal modeling an optimal therapy might be predicted. Schlieren techniques, generating high-speed and 'thermal' images, can provide a good understanding of the ablation mechanism and the thermo-dynamics during laser tissue interaction with continuous wave and pulsed lasers.

Original languageEnglish
Title of host publicationLaser-Tissue Interaction VI
Number of pages11
Publication statusPublished - 22 May 1995
Externally publishedYes
EventLaser-Tissue Interaction VI 1995 - San Jose, United States
Duration: 1 Feb 19958 Feb 1995

Publication series

NameProceedings of SPIE - the international society for optical engineering
ISSN (Print)0277-786X


ConferenceLaser-Tissue Interaction VI 1995
Country/TerritoryUnited States
CitySan Jose
OtherWorkshop at Photonics West 1995

Cite this