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SU‐D‐500‐05: Comparison of Gating Algorithms in 4D‐PET for Mobile Tumor Segmentation
Author(s) -
Jani S,
Dahlbom M,
White B,
Thomas D,
Gaudio S,
Low D,
Lamb J
Publication year - 2013
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 - 10.1118/1.4814022
Subject(s) - centroid , amplitude , segmentation , gating , volume (thermodynamics) , ground truth , bin , mathematics , physics , artificial intelligence , medical imaging , algorithm , nuclear medicine , geometry , computer vision , computer science , optics , medicine , physiology , quantum mechanics
Purpose: To quantitatively compare the accuracy of tumor volume segmentation in four different gating algorithms in gated 4D‐PET. Methods: Four acrylic spheres with inner diameters ranging from 1cm to 4cm were filled with a 11‐C solution and affixed inside a cylindrical bath of 18‐FDG. The system was attached to a robotic arm that underwent 1D motion according to large‐amplitude trajectories based on measured patient breathing trajectories. Two trajectories were used: one with and one without baseline drift. List‐mode data was split into two‐minute images at different source‐to‐background ratios (SBRs), which were gated into eight bins using two amplitude‐based (equal amplitude bins (A1) and equal counts per bin (A2)) and two temporal phased‐based gating algorithms. All gated images were segmented using a commercially available gradient‐based technique. Internal target volumes (ITVs), generated by taking the union of all eight contours per gated image, were compared to their respective ground truths. The ground‐truth ITV was defined as the volume subtended by the tumor model positions covering 99% of breathing amplitude. Superior‐inferior distances between sphere centroids in the end‐inhale and end‐exhale phases were also calculated. Results: Averaged over all sphere sizes, both trajectories, and high and low SBRs, A2 was the closest in accuracy of ITV segmentation, with a measured‐to‐expected ratio of 1.002 vs. 0.920 and 0.964 for temporal phase‐based methods (p<0.05). A1 consistently recovered the greatest volume and had the highest accuracy in the presence of irregular breathing, while A2 performed the best in accurately representing the smallest (1cm) sphere. Amplitude‐based methods consistently produced more distance between end‐inhale and end‐exhale phases than phase‐based methods (27.5% more on average), with A1 recovering up to 94% of peak‐to‐peak separation (p<0.01). Conclusion: Target volumes in images generated from amplitude‐based gating are more accurate, potentially at clinically significant levels, than those from temporal phase‐based gating. NIH R01 CA096679