Eckrich Carolyn, Lee Brandon, Wang Chunhao, Light Kim, Chino Junzo, Rodrigues Anna, Craciunescu Oana
Duke University Medical Center, Department of Radiation Oncology, Durham, North Carolina, USA.
MIM Software, Cleveland, Ohio, USA.
J Appl Clin Med Phys. 2025 Jan;26(1):e14538. doi: 10.1002/acm2.14538. Epub 2024 Oct 4.
To investigate dose differences between the planning CT (pCT) and dose calculated on pre-treatment verification CBCTs using DIR and dose summation for cervical cancer patients.
Cervical cancer patients treated at our institution with 45 Gy EBRT undergo a pCT and 5 CBCTs, once every five fractions of treatment. A free-form intensity-based DIR in MIM was performed between the pCT and each CBCT using the "Merged CBCT" feature to generate an extended FOV-CBCT (mCBCT). DIR-generated bladder and rectum contours were adjusted by a physician, and dice similarity coefficients (DSC) were calculated. After deformation, the investigated doses were (1) recalculated in Eclipse using original plan parameters (ecD), and (2) deformed from planning dose (pD) using the deformation matrix in MIM (mdD). Dose summation was performed to the first week's mCBCT. Dose distributions were compared for the bladder, rectum, and PTV in terms of percent dose difference, dose volume histograms (DVHs), and gamma analysis between the calculated doses.
For the 20 patients, the mean DSC was 0.68 ± 0.17 for bladder and 0.79 ± 0.09 for rectum. Most patients were within 5% of pD for D2cc (19/20), Dmax (17/20), and Dmean (16/20). All patients demonstrated a percent difference > 5% for bladder V45 due to variations in bladder volume from the pCT. D90 showed fewer differences with 19/20 patients within 2% of pD. Gamma rates between pD and ecD averaged 94% for bladder and 94% for rectum, while pD and mdD exhibited slightly better performance for bladder (93%) and lower for rectum (85%).
Using DIR with weekly CBCT images, the MIM deformed dose (mdD) was found to be in close agreement with the Eclipse calculated dose (ecD). The proposed workflow should be used on a case-by-case basis when the weekly CBCT shows marked difference in organs-at-risk from the planning CT.
研究宫颈癌患者计划CT（pCT）与使用DIR和剂量求和在治疗前验证CBCT上计算的剂量之间的差异。
在我们机构接受45 Gy EBRT治疗的宫颈癌患者进行一次pCT和5次CBCT，每五分次治疗进行一次。使用MIM中基于自由形式强度的DIR，通过“合并CBCT”功能在pCT和每次CBCT之间进行操作，以生成扩展视野CBCT（mCBCT）。由医生调整DIR生成的膀胱和直肠轮廓，并计算骰子相似系数（DSC）。变形后，所研究的剂量为：（1）在Eclipse中使用原始计划参数重新计算（ecD），以及（2）使用MIM中的变形矩阵从计划剂量（pD）变形得到（mdD）。对第一周的mCBCT进行剂量求和。比较膀胱、直肠和PTV的剂量分布，包括剂量百分比差异、剂量体积直方图（DVH）以及计算剂量之间的伽马分析。
对于20例患者，膀胱的平均DSC为0.68±0.17，直肠为0.79±0.09。大多数患者的D2cc（19/20）、Dmax（17/20）和Dmean（16/20）在pD的5%以内。由于膀胱体积与pCT存在差异，所有患者的膀胱V45百分比差异>5%。D90差异较少，19/20的患者在pD的2%以内。pD与ecD之间的伽马通过率膀胱平均为94% , 直肠为94%，而pD与mdD相比，膀胱表现稍好（93%），直肠较低（85%）。
使用DIR和每周的CBCT图像，发现MIM变形剂量（mdD）与Eclipse计算剂量（ecD）密切一致。当每周的CBCT显示危及器官与计划CT有明显差异时，建议的工作流程应逐案使用。
