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Automated Treatment Planning Approach with Beam Angles Optimization to Avoid Rib Bones Based On Similar Cases for Lung Stereotactic Body Radiation Therapy

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S Haseai

S Haseai1*, H Arimura1 , M Imai2 , T Yoshitake1 , Y Shioyama3 , H Honda1 , S Ohga1 , T Sasaki1 , (1) Kyushu University, Fukuoka-shi, Fukuoka-ken, Japan, (2) Kurume University Hospital, Kurume-shi, Fukuoka-ken, Japan, (3) Saga Heavy Ion Medical Accelerator in Tosu, Tosu-shi, Saga-ken, Japan


SU-I-GPD-T-600 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To develop an automated treatment planning approach with optimization of beam angles to avoid rib bones based on similar case for lung stereotactic body radiation therapy (LSBRT).

Methods: A radiation treatment plan database including 173 lung cancer cases and ten test cases was employed for this study. Ten similar cases were selected from the LSBRT database based on two-dimensional lung shape similarities in isocenter planes using Dice’s similarity coefficients. Five similar cases were chosen among the ten cases using five geometric features associated with lung and spinal cord. Initial beam configurations of the test cases were determined by using a three-dimensional (3D) affine linear registration between each similar case and the test case. The beam angle configurations of the five similar cases were optimized to avoid rib bones based on a cost function with taking into account water equivalent length (WEPL) of the patient body for correcting inhomogeneity of the body. The WEPL of the body was calculated by using computed tomography value and relative electron-density to water. Finally, dose evaluation indices for planning target volume, lung, spinal cord were calculated to select the most usable plans for the ten test cases and evaluate the proposed approach. We evaluated the proposed approach by comparing usable plans determined by the proposed approach and original plans designed by radiation oncologists.

Results: The usable plans, which had no significant difference from original plans determined by radiation oncologists, were made by the proposed approach. A dose evaluation index related to spinal cord was improved for some plans by the proposed approach in comparison with original plans and plans made by a method without using WEPL.

Conclusion: The proposed approach had a potential to automatically determine optimal beam angle configurations for avoiding rib bones based on similar cases in LSBRT.

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