Quantifying tumour hypoxia by PET imaging--a theoretical analysis.

Information on tumour oxygenation could be obtained from various imaging methods, but the success of incorporating it into treatment planning depends on the accuracy of quantifying it. This study presents a theoretical analysis of the efficiency of measuring tumour hypoxia by PET imaging. Tissue oxygenations were calculated for ranges of biologically relevant physiological parameters and were then used to simulate PET images for markers with different uptake characteristics. The resulting images were used to calculate dose distributions that could lead to predefined tumour control levels. The results have shown that quantification of tumour hypoxia with PET may lead to different values according to the tracer used and the tumour site investigated. This would in turn be reflected into the dose distributions recommended by the optimisation algorithms. However, irrespective of marker-specific differences, focusing the radiation dose to the hypoxic areas appears to reduce the average tumour dose needed to achieve a certain control level.