Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.788675
Title: Thermal imaging during laser surgery
Author: Gibson, Brian James
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1995
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Abstract:
This thesis considers the problems of remote temperature measurement, using a pyro-electric vidicon (PEV) to image small areas of biological tissue heated by laser irradiation. This is applied specifically to laser-assisted vascular anastomosis (LAVA), which is a surgical technique that aims to bond apposed tissue edges. It is a technique which has shown potential but the results have not been consistently successful. In order to understand the bond mechanism and to ascertain the optimum bond temperature, a number of authors have measured the temperature at the bond site using remote thermal imagers. However, if the limitations of the imager are not taken into account, then the temperature will be underestimated. These limitations were investigated extensively for the PEV but the principles apply to all thermal imagers. In particular, a minimum source width of 6 mm was required in order to avoid an underestimation of the temperature and considering the laser spot size was approximately 1.5 mm, large errors could be expected depending on the imager employed. In our case, errors of 20°C were measured. However, if we have adequate knowledge of the limitations of the imaging device, then a more realistic estimation of the temperature can be made by use of a computational model. A major part of the work presented here comprised of the development of a suitable model. Central to this was the determination of the point spread function (PSF) of the imager. This describes mathematically how a point in object space is imaged and the objective of the computational model is to run this process in reverse, that is to infer the object distribution from knowledge of the PSF and the image distribution. The PSF was found by two independent techniques, whose results were in close agreement. In order to assess the accuracy of the model another independent temperature measuring technique was required. A number were investigated, the most reliable being the picrosirius red staining technique which causes tissue to become optically inactive when viewed with polarised light if it is heated to a well defined threshold temperature. This temperature can readily be found and used to determine the accuracy of the model. It was found that the model could estimate tissue temperatures to an accuracy of 4°C.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.788675  DOI: Not available
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