As immuno-PET demonstrates significant potential in the development of mAb-based therapy, valid quantification is crucial in the interpretation of immuno-PET scans. This thesis focused on the validity and application of different quantification methods for the immuno-PET tracers [18F]F-AraG and 89Zr-mAbs, considering PET physics and tracer pharmacokinetics. The tumour uptake of [18F]F-AraG was characterized by an irreversible model, with TBR or TPR showing the most potential for valid simplified quantification. Similarly, a TBR or TPR was most reliable for quantifying tumour uptake of 89Zr-mAbs, particularly in the case of different mass doses that resulted in different 89Zr-mAb supply from plasma. For 89Zr-immuno-PET, further simplification of TBR could be achieved by quantifying the image-derived blood concentration. Using a delineation of a VOI from the ascending aorta results in the lowest overall bias and variability. Moreover, 89Zr-immuno-PET provides a non-invasive method to assess target engagement in organ tissue, either by quantifying the uptake exceeding the baseline value for non-specific uptake, or by increasing the mass dose resulting in a decrease in target-specific uptake. Lastly, biopsy-proven target-negative tumours showed some evidence for the presence of non-specific irreversible uptake of 89Zr-mAbs in tumours. Due to the presence of non-specific irreversible uptake, a TPR or TBR would always increase over time, also in the absence of the target.
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