An update on the penetration depth of 630 nm light in normal and malignant human brain tissue in vivo

In a recent paper (Wilson et al. ibid., vol.31, p.125-33, 1986) the authors described measurements of the effective penetration depth of 630 nm light in brain tissue, which were carried out in two patients receiving intra-operative photodynamic therapy for malignant brain tumours. Here, they present the results of further measurements on a total of eight patients using the same technique. For these studies they have, as far as possible, grouped the data according to whether the tissues measured were mainly normal cerebral brain tissue, mainly, malignant astrocytic tumour tissue or a mixture of normal and tumour tissues. This has enabled more direct comparison with published in vitro measurements of human brain tumour tissues (Svaasand and Ellingsen, Photo Chem. Photobiol., vol.38, p.293-9, 1983, Photochem. Photobiol., vol.41, p.73-6, 1985).