Abstract
PurposeThe purposes of this work are to (a) investigate whether the use of auto‐planning and multiple iterations improves quality of head and neck (HN) radiotherapy plans; (b) determine whether delivery methods such as step‐and‐shoot (SS) and volumetric modulated arc therapy (VMAT) impact plan quality; (c) report on the observations of plan quality predictions of a commercial feasibility tool.Materials and methodsTwenty HN cases were retrospectively selected from our clinical database for this study. The first ten plans were used to test setting up planning goals and other optimization parameters in the auto‐planning module. Subsequently, the other ten plans were replanned with auto‐planning using step‐and‐shoot (AP‐SS) and VMAT (AP‐VMAT) delivery methods. Dosimetric endpoints were compared between the clinical plans and the corresponding AP‐SS and AP‐VMAT plans. Finally, predicted dosimetric endpoints from a commercial program were assessed.ResultsAll AP‐SS and AP‐VMAT plans met the clinical dose constraints. With auto‐planning, the dose coverage of the low dose planning target volume (PTV) was improved while the dose coverage of the high dose PTV was maintained. Compared to the clinical plans, the doses to critical organs, such as the brainstem, parotid, larynx, esophagus, and oral cavity were significantly reduced in the AP‐VMAT (P < 0.05); the AP‐SS plans had similar homogeneity indices (HI) and conformality indices (CI) and the AP‐VMAT plans had comparable HI and improved CI. Good agreement in dosimetric endpoints between predictions and AP‐VMAT plans were observed in five of seven critical organs.ConclusionWith improved planning quality and efficiency, auto‐planning module is an effective tool to enable planners to generate HN IMRT plans that are meeting institution specific planning protocols. DVH prediction is feasible in improving workflow and plan quality.
Highlights
Head and neck (HN) cancer is a technically challenging treatment site in radiation oncology due to the complex anatomy and numerous organs at risk (OARs) in close proximity to targets
Treatment planning techniques for HN cancer have advanced from the conventional three‐field technique to intensity modulated radiation therapy (IMRT) over two decades.[1]
The automatic planning tool developed by the Pinnacle (Philips Radiation Oncology Systems, Fitchburg, WI) commercial treatment planning system is to mimic the manual processes of skilled planners by progressively and iteratively adjusting and adding planning objectives, which may mitigate the shortcoming of the gradient‐based optimization.[10]
Summary
Head and neck (HN) cancer is a technically challenging treatment site in radiation oncology due to the complex anatomy and numerous organs at risk (OARs) in close proximity to targets. To achieve adequate target coverage while protecting numerous OARs, IMRT plans for HN cancer require highly conformal dose distributions and a steep dose fall‐off between the boundary of tumor volumes and sensitive structures. The predicted dose volume histograms (DVHs) are based on energy‐specific dose spread calculation, reflecting the characteristics of photon dose distribution in media.[8]. Another approach to robust planning is to create many planning solutions (multicriteria optimization) for a single clinical case so that clinicians can make a decision based on the trade‐off among the dose coverage of the tumor volume and protections of sensitive structures.[9]. A planner would be equipped with all of these tools: a tool that can reliably predict achievable DVHs as initial inputs of the planning objectives, a tool that can automatically and progressively adjust planning objectives, and a tool that can offer multiple solutions based on different trade‐offs
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