Program Information
Quantifying Organ Motion During Deep Inspiration Breath-Hold SBRT of Upper Abdominal Targets Using 4D Ultrasound
D Sihono1*, L Vogel1 , F Lohr2 , H Wertz1 , A Simeonova-Chergou1 , F Wenz1 , J Boda-Heggemann1 , (1) Department of Radiation Oncology, Universitaetsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany, (2) Struttura Complessa di Radioterapia, Dipartimento di Oncologia, Az. Ospedaliero-Universitaria di Modena, Modena, Italy
Presentations
SU-K-605-6 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 605
Purpose: Deep inspiratory breath-hold (DIBH) has been used to reduce treatment margins due to respiratory organ motion for upper abdominal targets during Stereotactic Body Radiotherapy (SBRT). Residual errors, reproducibility of breath-hold (BH), deformations and organ position still have to be considered. This study aims at quantifying residual target motion during BH using 4D real time tracking ultrasound (US).
Methods: 12 PTVs of 11 patients with primary/secondary liver tumours or adrenal gland/spleen metastases of diverse primaries were irradiated with SBRT in DIBH. Real time tracking of target or neighbouring surrogate structures was performed additionally using 4D US system during CBCT acquisition after permission of local IRB. Residual intrafractional motion of tracking target relative to beginning position in each BH plateau region was analysed along three directions; superior-inferior (SI), left-right (LR) and anterior-posterior (AP).
Results: 680 individual BHs during 93 treatment fractions were analysed. On visual control of result, target was lost in 27.9% of tracking, leaving a total of 490 BHs with optimal tracking. During these BHs, mean(±SD) target displacement were 1.7(±0.8)mm, 0.9(±0.4)mm, 2.2(±1.0)mm and 3.2(±1.0)mm for SI, LR, AP and 3D vector, respectively. Most of target displacement was below 2mm with percentage of 64.6%, 88.1% and 60.5% for SI, LR and AP, respectively. Data percentage of large target displacement increased with added BH time. At 5s, 3D vector of target displacement >10mm could be observed in 0.1% of data. Percentage values increased to 0.2%, 0.6%, and 1.1% at 10s, 15s and 20s, respectively.
Conclusion: Exact quantification of residual motion impact requires an in-depth analysis of time spent at every position, nevertheless mean residual motion in DIBH is low and predominant direction is SI and AP. Only infrequently larger displacements of 3D vector >1cm were observed, for short periods. Beam interruption at predefined thresholds could take DIBH treatments close to perfection.
Funding Support, Disclosures, and Conflict of Interest: D. Sihono, L. Vogel: no conflict of interests, F. Lohr, H. Wertz, A. Simeonova-Chergou, J. Boda-Heggemann: research grant and teaching honoraria form Elekta, F Wenz: research grant, teaching honoraria from Elekta and works as consultant and for the advisory board of Elekta.
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