1. Using equivalent illumination doses, photodegradation of Cle₆ is more rapid and complete than that of other investigated compounds. Cle₆ forms no photoproducts and photochemical dose can be calculated by the equation (2).

2. At illumination doses, commonly used in PTT, AlPcS₄ is sufficiently photostable, and we do not observe any spectral changes reflecting its photomodification. Thus, a photochemical dose for AlPcS₄, especially at low illumination doses can be calculated by the simple geometrical definition PD=D₀J₀.

3. In the case of haematoporphyrin-type photosensitizers, which tend to form the red-absorbing photoproducts efficiently, the correction related to the formation of the active photoproduct should be included in calculations of the appropriate photochemical dose for PTT (equation (3)), when illumination is carried out at wavelengths covered by the absorption region of the photoproduct, since the formed photoproduct itself can act as photosensitizer and induce the additional photodynamic effect [17].

ACKNOWLEDGMENTS

This work has been supported by the Lithuanian State foundation of Science and Studies. The cooperation of R.Wendenburg and W.Dietel (Jena University, Jena, Germany), L.Griciute, J.Didziapetriene and L.Staciokiene (Lithuanian Oncology Center, Vilnius, Lithuania) and the skilled assistance of G.Streckytë and S.Bagdonas in assembly and presentation of this manuscript as well as A.Jasaitis, P.Juzenas and V.Gudelis assistance in the spectroscopic experiments are gratefully acknowledged.