Abstract：Objective To explore the depth-dose characteristics in Eclipse radiotherapy treatment planning system for inhomogeneous
tissues. Methods In the Eclipse treatment planning system, a water phantom of 30 cm×30 cm×30 cm and an inhomogeneous
medium of lung tissue or bone tissue with a thickness of 3 cm was set up at a depth of 3 cm, and CT value was assigned to the tissue
materials. The source skin distance was set to 100 cm while the field size were set as 5 cm×5 cm, 10 cm×10 cm, 15 cm×15 cm,
20 cm×20 cm. The dose size was 100 cGy, and 6 MV X-ray irradiation was used, and the AXB algorithm was selected based on the
Monte Carlo results to obtain the horizontal and vertical dose curves on the central axis of the phantom. Results The longitudinal
depth dose increased first and then decreased with the increase of depth, and the larger the field area, the greater the relative dose;
a second dose build-up was established at the junction of the lung or bone tissue phantom and the water tissue. In the longitudinal
depth dose curve of water-lung-water inhomogeneous tissue, at a depth of 3 cm, water entered the lung tissue. Duo to the lack of
backscatter, the dose decreased rapidly. When the beam penetrated the lungs, due to lack of scattering, the dose was lower than
that through the water tissue, and the dose increased at a depth of 6 cm, with a maximum increase of 2.28%. In the longitudinal
depth dose curve of water-bone-water non-uniform tissue, at a depth of 3 cm, water entered the bone tissue, and the dose decreased
steadily. There was significant difference in the horizontal central axis water-lung-water and water-bone-water isodose curves under a
20 cm×20 cm field. The transverse depth dose decreased by 10.78% when entering lung tissue from water, and increased by 10.61%
when entering water tissue from lung. The inhomogeneous tissue in the water-bone-water tissue had little effect. Conclusion The
AXB algorithm of the Eclipse radiotherapy planning system is more suitable for the dose calculations of inhomogeneous tissue. A
secondary build-up effect will occur. The radiotherapy plan designer should pay attention to the dose on the inhomogeneous medium
interface.
彭圣贤a,b，庞亚b，吴哲b. Eclipse放疗计划系统内非均匀组织深度剂量特性研究[J]. 中国医疗设备, 2022, 37(7): 45-48.
PENG Shengxiana,b, PANG Yab, WU Zheb. Study on the Depth-Dose Characteristics in Eclipse Radiotherapy Treatment
Planning System for Inhomogeneous Tissues. China Medical Devices, 2022, 37(7): 45-48.
