Program Information
The Long- and Short-Term Variability of Breathing-Induced Tumor Motion in Lung and Liver Over the Course of a Radiotherapy Treatment
J Dhont1*, D Verellen2 , J Vandemeulebroucke3 , M Burghelea4 , K Poels5 , R Van den Begin6 , C Jaudet7 , T Gevaert8 , B Engels9 , C Collen10 , M de Ridder11 , (1) Universitair Ziekenhuis Brussel, Brussels, Jette, (2) GZA Ziekenhuizen, Sint Augustinus - Iridium Kankernetwerk Antwerpen, Antwerpen, Antwerpen, (3) Vrije Universiteit Brussel, Brussels, ,(4) Universitair Ziekenhuis Brussel, Brussels, BRUSSELS, (5) Universitair Ziekenhuis Leuven, Leuven, Leuven, (6) Universitair Ziekenhuis Brussel, Brussels, ,(7) Uni, Brussels, ,(8) Universitair Ziekenhuis Brussel, Brussels, ,(9) Universitair Ziekenhuis Brussel, Brussels, ,(10) Universitair Ziekenhuis Brussel, Brussels, ,(11) Universitair Ziekenhuis Brussel, Brussels, Jette
Presentations
SU-I-GPD-J-64 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To evaluate the short and long-term variability of breathing-induced tumor motion.
Methods: 3D tumor motion of 19 lung and 18 liver lesions, captured over the entire course of treatment, was evaluated and compared to the motion on 4D-CT. An implanted fiducial could be used for unambiguous motion information. Fast orthogonal fluoroscopy (FF) sequences, included in the treatment workflow, were used to evaluate motion during treatment.Baseline drift, hysteresis and motion amplitude were compared between different FF sequences from the same fraction to evaluate the intrafraction variability. To assess interfraction variability, amplitude and hysteresis were compared between fractions and with the 3D tumor motion registered by 4D-CT. Statistical analysis was performed to evaluate possible correlations between motion parameters.
Results: While intrafraction variability mostly remains below common treatment margins of 5 mm, baseline drift - a type of short-term deformation that can have significant dosimetrical consequences when not taken into account during hypofractionation or heavy ion and proton therapy - is significant for a large group of patients. Interfraction variability in mean motion amplitude is significant in 51% of all lesions, with 20% expressing interfraction variability of more than 10 mm. As such, 4D-CT is not capable of accurately capturing the motion during all treatment fractions. This is especially cumbersome when 4D-CT is used for passive motion management strategies, such as ITV or mid-ventilation.A correlation between intrafraction amplitude variability and mean motion amplitude was observed (p < 0.0001 ). The same correlation for interfraction amplitude was also present but less pronounced (p < 0.05). Significant correlations between motion variability and lesion characteristics such as volume, location and pathology were not present.
Conclusion: Day-to-day tumor motion variability can be significant and indicates the necessity for real-time motion monitoring, especially for those tumors moving in the order of one centimeter and more.
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