Room: AAPM ePoster Library
Purpose: To test the correlation between lung tumor motion and three anchored beacons during 10 phases of 4DCT to determine the best treatment delivery approach.
Methods: A 4DCT and Breath Hold BH-CT for patient receiving SBRT, 50 Gy in 5 fractions, to right upper lung lobe were obtained. The patient had three electromagnetic transpondeers implanted in the RT lung to track and possibly gate patient's treatment with Calypso System. Lung tumor motion was analyzed using the 10 4DCT phases (CT0 to CT90), BH-CT and maximum intensity projection CT MiP to determine tumor motion excursions. The motion of the three transponders was analyzed in Anterior/Posterior, Superior/Inferior, and Left/Right directions for all 10 phases with respect to BH-CT. Spearman correlation coefficients were used to assess correlations between all three beacons motion individually and on average with tumor motion in each single phase (CT0 to CT90).
Results: There was no significant correlation between beacons motion and tumor motion during the 4DCT acquisition (p>0.05) in any direction AP, SI, or LR. Which limits the capability of relying on the beacons for free breathing gated treatment delivery, however breath hold gating is still viable as a safer choice.
Conclusion: It is a standard practice to assess tumor motion in the 4DCT acquisition during all phases and MiP CT for deriving margins and determining the treatment delivery modality (free breathing phase
or amplitude gating, or breath hold). However, it is crucial also to examine the beacons motion throughout the 4DCT phases to evaluate the correlation between the tumor motion and beacons motion for safer tumor margins, more realistic tracking motion limits presets, and gating if feasible. Our work is still in progress to analyze more patients' beacons motion with respect to tumor motion using 4DCT phases.
Not Applicable / None Entered.