DETERMINATION OF THE OPTICAL PENETRATION DEPTH IN TUMORS FROM BIOPSY SAMPLES

Abstract
The laser treatment of malignant tumors by photochemotherapy encounters several physical problems one of which is insufficient knowledge of the light penetration. Since the penetration depth may vary considerably from tumor to tumor it must be measured before the treatment in order to allow one to achieve a well defined photochemical effect. The method proposed here consists of two steps : 1 - Each tumor is characterized individually by two parameters which are obtained by goniometric measurement of the light crossing a small sample (1 mm³). These parameters can be easily determined in a clinical environment but provide no direct information on the light distribution in the bulk. 2 - The above parameters are related with the effective penetration depth for geometries and wavelengths of practical relevance. The relationship is established experimentally by multiple measurements in phantoms which are composed so as to approach closely the optical properties of tumors.