forecast. 
In an experimental setup known tissues and 
precision reference beads were used to build up 
the tissue-specific — correction database. 
QUASIA3D's algorithms were then used to 
estimate the dye concentration of phantom 
specimens consisting of tissue of the same type 
submerged in photosensitizer solutions of 
varying concentration. The light loss between 
the first few slices and slices far under the 
phantoms varied between 50% to 80%. For all 
slice levels QUSAIA3D's dye concentration 
estimation was within a 15% error bound. 
7. CONCLUSIONS 
A critical aspect for the success of PDT as a 
viable cancer treatment modality is besides a 
thorough understanding of the basic 
mechanisms involved in this technique, the 
ability to select and apply optimal tumor 
treatment conditions. This includes, as a 
prerequisite, the quantification of the local 
sensitizer dye concentration within cells or cell 
colonies. 
Confocal laser scanning microscopy offers 
an efficient way to acquire 3D-image data sets 
of tumor cells or tissue for postliminary 
quantitative analysis. This paper outlines the 
various impeding effects which need to be 
accounted for if photosensitizer dye 
concentrations are estimated from stacks of 
CLSM data. 
To this end an elaborate set of models and 
procedures were devised and implemented 
which allow to build an instrument-, dye- and 
tissue specific correction database. This 
database is then used to reconstruct the CLSM 
image stacks. 
8. REFERENCES 
] Lin C. W.. "Photodynamic Therapy of 
318 
Malignant Tumors - Recent Development", 
Cancer Cells, Vol. 3, No. 11, 437 - 444, 
November 1991 
Brunner B., Burkard W., Steiner R. A, 
WaltH.: "The behaviour of tumor cells of 
gynaecological origin in vitro after addition 
of photosensitizer in PDT", Arch. Gynaecol, 
Vol. 252 Suppl., 110ff, 1992 
Leemann T., Walt H., Margadant F, 
Guggiana V., Anliker M: "Computer 
assisted 3D-analysis of Photodynamic effects 
in living cancer cells", XVII ISPRS 
Congress, Washington DC, August 2 - 14, 
1902 
Leemann T., Margadant F., Walt H., Jentsch 
B., Haller U., Anliker M.: "Computer 
assisted 3D-Microscopy in Gynaecology: 
Photodynamic Therapy of Cancer Cells", 
ISPRS Commision V  Intercongress 
Symposium, Melbourne, Australia, March 
] - 4, 1994 
Ris H.-B. et al: "Clinical evaluation of 
photodynamic therapy with mTHPC for 
chest malignancies", Photodynamic Therapy 
and Biomedical Lasers, Elsevier, 421-425, 
1992 
Wilson T., Sheppard C. "Theory and 
Practice of Scanning Optical Microscopy", 
Academic Press, 1984 
Pawley J. B.: "Handbook of Biological 
Confocal Microscopy", Plenum Press, 1990 
F. Margadant, T. Leemann, P. Niederer: "A 
precise light attenuation correction for 
confocal scanning microscopy with O(n^) 
computing time and O(n) memory require- 
ments for n voxels", Journal of Microscopy, 
Vol. 181, Pt 3, March 1996 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996 
  
KEY Wt 
ABSTR/ 
A new L 
Hydrogre 
This sys 
impleme 
technolo; 
Recent te 
Explorat 
importan 
marine 
investiga 
key to 
imaging 
Advance 
in solid 
underwa 
effective 
of under 
1992). 
À resear 
and the 
mobile 
fisheries 
emphasi 
identific 
volume, 
Traditio: 
manager 
Howeve: 
video 1 
interpre! 
technolo 
underwa 
photogr: 
applicat 
The qua 
images 
processi 
This pa; 
System 
and CH, 
configur