Impact of PET reconstruction algorithm and threshold on dose painting of non-small cell lung cancer

PURPOSE: In the current work, we investigate the impact of PET reconstruction methods (RMs) and threshold on two types of dose painting (DP) prescription strategies for non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS: Sixteen patients with NSCLC underwent an 18F-FDG-PET/CT examination prior to radiotherapy. Six different RMs were used. For both a dose painting by contours (DPBC) and a dose painting by numbers (DPBN) strategy, the prescribed radiation dose within the gross tumor volume (GTV) was mapped according to the spatial distribution of standardized uptake values (SUVs). SUVmax and SUVpeak were used for volume thresholding in DPBC and a linear SUV-dose scaling approach was used for DPBN. Deviations from the dose prescription as determined by the standard RM was scored by a quality factor (QF).

RESULTS: For DPBC, the mean difference in thresholded boost volume between RMs was typically within 10%. The difference in dose prescription was systematically lower for thresholding based on SUVpeak (largest mean QF 2.8±2.0%) compared to SUVmax (largest mean QF 3.6±3.0%). For DPBN, the resulting dose prescriptions were less dependent on RM and threshold; the largest mean QFs were 1.3±0.3% both for SUVmax and SUVpeak.

CONCLUSIONS: PET reconstruction algorithms will both influence DPBC and DPBN, although the impact is smaller for DPBN. For some patients, the resulting variations in dose prescriptions may result in clinically different dose distributions. SUVpeak is a more robust thresholding parameter than SUVmax.