Page 129 - 89Zr-Immuno-PET:Towards a Clinical Tool to Guide Antibody-based Therapy in Cancer
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                                Interobserver reproducibility of 89Zr-immuno-PET
 Figure 2 VOI delineation methods for 89Zr-immuno-PET 6
Manual tumor delineation on immuno-PET (a) using the low dose CT (left panel), attenuation corrected 89Zr-cetuximab-PET on D6 (middle panel) with tumor lesion indicated by the red arrow and example VOI on 89Zr-cetuximab-PET shown in green (right panel).
Manual tumor delineation on immuno-PET after reviewing the corresponding 18F-FDG-PET (b) the original manually delineated VOI shown in green on the 89Zr-trastuzumab-PET on D4 (left panel), reviewing the 18F-FDG-PET scan with tumor lesion indicated by the red arrow (middle panel) and adapting the original VOI after reviewing the 18F-FDG-PET scan, the FDG adapted tumor VOI shown on 89Zr-trastuzumab-PET is in green (right panel). Semi-automatic delineation (c) with the attenuation corrected 89Zr-rituximab-PET on D6 (left panel), the mask delineated on the 89Zr-rituximab-PET shown in orange (middle panel) and the semi- automatic VOI (50% of ACpeak, mask restricted) on the 89Zr-rituximab-PET shown in green (right panel). This semi-automatic VOI was accepted by the observer, as it contains tumor and no other structures or background.
Eligibility criteria for VOI delineation
Quantification of lesions with low tumor uptake and/or high background uptake (e.g. lesions with low contrast and/or nearby presence of blood vessels or elevated healthy tissue uptake) is difficult, due to the intrinsically low signal to noise ratios in 89Zr-immuno-PET. To ensure that quantification is only reported when delineation is feasible, a method to determine eligibility for VOI delineation was explored. Criteria were selected based on the potential for incorporation in a standardized workflow for tumor identification by a nuclear medicine physician, followed by tumor delineation by a data-analist.
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