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MO‐E‐AUD C‐01: Dosimetric Differences for Dose Painting, Based On SUV Or KFLT FLT‐PET Image Ratio
Author(s) -
Jeraj R,
Simoncic U,
Flynn RT,
Bowen ST
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2962390
Subject(s) - nuclear medicine , dosimetry , voxel , medicine , radiation therapy , medical imaging , radiation treatment planning , pet ct , positron emission tomography , radiology
Purpose: One of the most important properties for biologically‐based radiotherapy (dose painting) is accurate definition of the treatment target. Here we investigate consequences of non‐uniform dose escalation based on proliferative response, when the treatment target is defined on FLT‐PET standardized uptake values (SUV) as opposed to the parametric image parameters KFLT obtained through compartmental modeling. Method and Materials: Patients were imaged with FLT‐PET before the start and after one to two weeks of radiation therapy. The SUV images and KFLT parametric images were calculated from dynamically acquired PET data. Mid‐therapy images were co‐registered with pre‐treatment images, and ratios of mid‐treatment to pre‐treatment SUV or KFLT images were calculated. These ratios were connected to spatially‐dependant radiosensitivity according to the linear‐quadratic survival model. The two continuous voxel‐based dose painting treatment plans were compared to each other and to the uniform dose escalation treatment plan. Results: Calculated SUV and KFLT images show similar, although distinctively different visual patterns. Ratios of SUV or KFLT images show increased spatial heterogeneity compared to the original images. Correlation of the ratio images is comparable to the correlation of individual SUV or KFLT images. Dosimetric evaluation of the plans revealed that approximately 25% of the target volume received more than 10% different dose for the SUV ratio prescription compared to the KFLT ratio prescription. On the other hand, the SUV ratio dose painting plan was clearly superior to the uniform dose escalation plan where over 75% of the target volume received more than 10% different dose. Conclusion: Dose painting using the prescriptions based on SUV or KFLT leads to significantly different treatment plans; however, their differences are smaller than the differences to the uniform dose escalation. These differences warrant careful clinical investigation to establish superiority of either prescription.