PURPOSE: To quantify the rotational offsets and estimate the dose effect of rotation on the target volume and normal tissues in children with brain tumor. METHODS: Twenty-one pediatric patients with brain tumors were included in this study. Cone-beam CT was performed before each treatment and at the end of every other treatment. Translational offsets were corrected before the treatment. An offline analysis was performed to quantify rotational errors. The treatment plans were altered and recalculated to simulate a rotation of 2° and 4°, and the dose changes were quantified. RESULTS: 1016 CBCT datasets were analyzed for this report. The mean of the rotations were not meaningfully different from zero. 18.1% of the fractions had rotations with a magnitude ≥2°, 5.0% had rotations ≥3° and 0.9% had rotations ≥4°. For the 2° rotational simulation, the gEUD values of the PTV and critical structures changed by less than 2%. For the 4° simulation, parallel type normal structures had minor changes (<2%), but serial type normal structures and the PTV had changes of 10% and 5%, respectively. CONCLUSIONS: The majority of rotational errors observed were less than 1°. A rotational error of 2° produced negligible changes in the gEUD to critical structures or target volumes. Rotational errors ≥4° produced undesirable results, therefore, at a minimum, errors >2° should be corrected.
PURPOSE: To quantify the rotational offsets and estimate the dose effect of rotation on the target volume and normal tissues in children with brain tumor. METHODS: Twenty-one pediatric patients with brain tumors were included in this study. Cone-beam CT was performed before each treatment and at the end of every other treatment. Translational offsets were corrected before the treatment. An offline analysis was performed to quantify rotational errors. The treatment plans were altered and recalculated to simulate a rotation of 2° and 4°, and the dose changes were quantified. RESULTS: 1016 CBCT datasets were analyzed for this report. The mean of the rotations were not meaningfully different from zero. 18.1% of the fractions had rotations with a magnitude ≥2°, 5.0% had rotations ≥3° and 0.9% had rotations ≥4°. For the 2° rotational simulation, the gEUD values of the PTV and critical structures changed by less than 2%. For the 4° simulation, parallel type normal structures had minor changes (<2%), but serial type normal structures and the PTV had changes of 10% and 5%, respectively. CONCLUSIONS: The majority of rotational errors observed were less than 1°. A rotational error of 2° produced negligible changes in the gEUD to critical structures or target volumes. Rotational errors ≥4° produced undesirable results, therefore, at a minimum, errors >2° should be corrected.
Authors: Eugene Huang; Bin S Teh; Douglas R Strother; Quillin G Davis; J Kam Chiu; Hsin H Lu; L Steven Carpenter; Wei Yuan Mai; Murali M Chintagumpala; Michael South; Walter H Grant; E Brian Butler; Shiao Y Woo Journal: Int J Radiat Oncol Biol Phys Date: 2002-03-01 Impact factor: 7.038
Authors: Nanna M Sijtsema; Alfons C M van den Bergh; Fred R Burlage; Henk P Bijl; Johannes A Langendijk; Harm Meertens Journal: Radiother Oncol Date: 2007-02-15 Impact factor: 6.280
Authors: Yvonne R J van Herten; Jeroen B van de Kamer; Niek van Wieringen; Bradley R Pieters; Arjan Bel Journal: Radiother Oncol Date: 2008-04-23 Impact factor: 6.280