Cone-beam CT (CBCT) based cervical brachytherapy (CBCT-BT) is promising to simplify treatment workflow and improve the accuracy of dose delivery. However, severe artifacts in CBCT and its impact on dose calculation should be carefully investigated. In this work, we developed a novel female pelvis phantom dedicated to the cervical brachytherapy, which could be used to evaluate the CBCT-BT performance on imaging accuracy and dose calculation. The phantom dimension and organ position were determined based on Asian female patients. The phantom mainly simulates four parts: adipose, bone, muscle, organs. The first three parts are fixed, and peanut oil, PMMA, POM and PTFE are used to mimic adipose, muscle, cortical bone and cancellous bone respectively. In the muscle, there are four cavities for the insertion of 3D-printed deformable and moveable organs, i.e., vagina and uterus, bladder, intestine, rectum. The vagina and uterus were connected, with a 2 mm diameter elastic channel in it to enable applicator movement. To evaluate the CBCT-BT performance, a standard planning CT (pCT) scan and a CBCT scan were conducted on this phantom, scatter removal algorithm using pCT prior was implemented on the CBCT images. The HU error of muscle, adipose, and organs-at-risk (OARs) in corrected CBCT images were less than 15 HU. Referred to pCT-based plan as baseline, the CBCT-based plan achieved a γ pass rate of >97%. In conclusion, this created phantom successfully simulate both the anatomy structure and the HU numbers of female pelvis, thus provides an effective tool for CBCT-BT evaluation.
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