Page 27 - Organ motion in children for high-precision radiotherapy - Sophie Huijskens

Abstract
Purpose: To quantify renal and diaphragmatic interfractional motion in order to estimate systematic and random errors, and to investigate the correlation between interfractional motion and patient- specific factors.
Methods: We used 527 retrospective abdominal-thoracic cone beam CT scans of 39 childhood cancer patients (<18 years) to quantify renal motion relative to bony anatomy in the left-right (LR), cranio- caudal (CC) and anterior-posterior (AP) directions, and diaphragmatic motion in the CC direction only. Interfractional motion was quantified by distributions of systematic and random errors in each direction (standard deviations Σ and σ, respectively). Also, correlation between organ motion and height was analyzed.
Results: Inter-patient organ motion varied widely, with the largest movements in the CC direction. Values of Σ in LR, CC, and AP directions were 1.1, 3.8, 2.1 mm for the right, and 1.3, 3.0, 1.5 mm for the left kidney, respectively. The σ in these three directions was 1.1, 3.1, 1.7 mm for the right, and 1.2, 2.9, 2.1 mm for the left kidney, respectively. For the diaphragm we estimated Σ = 5.2 mm and σ = 4.0 mm. No correlations were found between organ motion and height.
Conclusions: The large inter-patient organ motion variations and the lack of correlation between motion and patient-related factors, suggest that individualized margin approaches might be required.
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