Abstract
A recent publication indicated that the patient anatomical feature (PAF) model was capable of predicting optimal objectives based on past experience. In this study, the benefits of IMRT optimization using PAF‐predicted objectives as guidance for prostate were evaluated. Three different optimization methods were compared. 1) Expert Plan: Ten prostate cases (16 plans) were planned by an expert planner using conventional trial‐and‐error approach started with institutional modified OAR and PTV constraints. Optimization was stopped at 150 iterations and that plan was saved as Expert Plan. 2) Clinical Plan: The planner would keep working on the Expert Plan till he was satisfied with the dosimetric quality and the final plan was referred to as Clinical Plan. 3) PAF Plan: A third sets of plans for the same ten patients were generated fully automatically using predicted DVHs as guidance. The optimization was based on PAF‐based predicted objectives, and was continued to 150 iterations without human interaction. DMAX and D98% for PTV, DMAX for femoral heads, DMAX, D10cc, D25%/D17%, and D40% for bladder/rectum were compared. Clinical Plans are further optimized with more iterations and adjustments, but in general provided limited dosimetric benefits over Expert Plans. PTV D98% agreed within 2.31% among Expert, Clinical, and PAF plans. Between Clinical and PAF Plans, differences for DMAX of PTV, bladder, and rectum were within 2.65%, 2.46%, and 2.20%, respectively. Bladder D10cc was higher for PAF but <1.54% in general. Bladder D25% and D40% were lower for PAF, by up to 7.71% and 6.81%, respectively. Rectum D10cc, D17%, and D40% were 2.11%, 2.72%, and 0.27% lower for PAF, respectively. DMAX for femoral heads were comparable (<35 Gy on average). Compared to Clinical Plan (Primary+Boost), the average optimization time for PAF plan was reduced by 5.2 min on average, with a maximum reduction of 7.1 min. Total numbers of MUs per plan for PAF Plans were lower than Clinical Plans, indicating better delivery efficiency. The PAF‐guided planning process is capable of generating clinical‐quality prostate IMRT plans with no human intervention. Compared to manual optimization, this automatic optimization increases planning and delivery efficiency, while maintaining plan quality.PACS numbers: 87.55.D‐, 87.55.de, 87.53.Jw
Highlights
Intensity-modulated radiation therapy (IMRT) has been widely used to treat early stage prostate cancer and yields good clinic results
IMRT planning for a specific patient is achieved by iteratively reducing dose to organs at risk (OARs) in a trial-and-error fashion until the dose distribution is believed to be optimal for that patient
Planning quality comparison All the Expert, Clinical, and patient anatomical features (PAF) Plans satisfied the basic clinical standard as they all met the institutional objectives for bladder, rectum, and femoral heads
Summary
Intensity-modulated radiation therapy (IMRT) has been widely used to treat early stage prostate cancer and yields good clinic results. IMRT planning for a specific patient is achieved by iteratively reducing dose to OARs in a trial-and-error fashion until the dose distribution is believed to be optimal for that patient. Lack of achievable patient-specific OAR sparing information makes this manual approach time-consuming. From another perspective, with IMRT being implemented clinically for nearly two decades, experience and knowledge have been built and accumulated. With IMRT being implemented clinically for nearly two decades, experience and knowledge have been built and accumulated Such expert knowledge has been implicitly built into each clinical approved plan created by expert radiation oncologists and planners. Learning from prior plans to predict patient-specific optimal dose sparing is an innovative use of expert’s knowledge
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