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6 
  
  
QUANTITATIVE 3D-MICROSCOPY FOR PHOTODYNAMIC THERAPY 
OF CANCER CELLS 
Leemann Th, Margadant F, Walt H', Niederer P 
Institute of Biomedical Engineering and Medical Informatics (IBTZ), University of Zürich and 
Swiss Federal Institute of Technology (ETHZ) in Zürich, Switzerland 
? Department of Gynaecology and Obstetrics, University Hospital, Zürich, Switzerland 
Commision V, Working Group 5 
KEY WORDS: Medicine, Acquisition, Correction, Algorithms, Quantitative 3D-microscopy, 3D- 
image processing, Photodynamic Tumor Therapy 
ABSTRACT 
Localization and eradication of tumor cells without affecting or damaging normal tissue is a 
challenging target in today's cancer therapy. This objective could soon be viable through the use of 
Photodynamic Therapy (PDT), a promising tumor treatment modality based on the combined 
application of laser light in conjunction with a photosensitizing agent. Appropriate sensitizer show 
a preferential accumulation in tumor cells where they become cytotoxic by producing singlett 
oxygen after illumination with light of a specific wavelength. : 
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 address the specific needs for quantitative 3D-microscopic investigations 
efficient tools and procedures for image enhancement and restoration, interactive identification, 
segmentation and 3D-analysis of cell structures or cell colonies are a prerequisite. 
1. INTRODUCTION 
The more traditional forms of cancer 
treatment like surgery, irradiation by X-rays or 
chemotherapy are most widely applied and have 
proved to be successful. These treatment 
modalities present, however, disadvantages 
such as invasiveness, considerable side effects, 
often unspecific targeting of the tumor tissue 
and the inability to act down to the single cell 
level. 
Localization and eradication of tumor cells 
without affecting or damaging normal tissue is a 
challenging goal in today's cancer therapy. This 
313 
objective may soon become a reality thanks to a 
promising cancer treatment modality named 
Photodynamic Therapy (PDT) [1, 5] which has 
the potential to selectively destroy benign as 
well as malignant proliverative cells. 
In 1994 the US Federal Drug Administration 
(FDA) approved the use of PDT as a valid 
tumor therapy. 
PDT presupposes the preferential absorption 
of photosensitive agents, such as hematopor- 
phyrin derivatives  (phtalocyanines and 
chlorines among others) by cancerous cells. The 
accumulated sensitizer is non-toxic until 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996