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KMID : 1038720140250040242
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Progress in Medical Physics
2014 Volume.25 No. 4 p.242 ~ p.247
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Discrepancies between Calculated and Delivered Dose Distributions of Respiratory Gated IMRT Fields according to the Target Motion Ranges for Lung and Liver Cancer Patients
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Kim Young-kuk
Ro Tae-Ik
Jeung Tae-Sig
Ma Sun-Young
Choi Ji-Hoon
Lim Sang-Wook
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Abstract
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To see the discrepancies between the calculated and the delivered dose distribution of IMRT fields for respiratory-induced moving target according to the motion ranges. Four IMRT plans in which there are five fields, for lung and liver patients were selected. The gantry angles were set to 0° for every field and recalculated using TPS (Eclipse Ver 8.1, Varian Medical Systems, Inc., USA). The ion-chamber array detector (MatriXX, IBA Dosimetry, Germany) was placed on the respiratory simulating platform and made it to move with ranges of 1, 2, and 3 cm, respectively. The IMRT fields were delivered to the detector with 30~70% gating windows. The comparison was performed by gamma index with tolerance of 3 mm and 3%. The average pass rate was 98.63% when there's no motion. When 1.0, 2.0, 3.0 cm motion ranges were simulated, the average pass rate were 98.59%, 97.82%, and 95.84%, respectively. Therefore, ITV margin should be increased or gating windows should be decreased for targets with large motion ranges.
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KEYWORD
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Gated radiation therapy, IMRT, Gamma index, Moving phantom
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