Abstract
BackgroundIntensity modulated radiotherapy treatment planning for sites with many different organs-at-risk (OAR) is complex and labor-intensive, making it hard to obtain consistent plan quality. With the aim of addressing this, we developed a program (automatic interactive optimizer, AIO) designed to automate the manual interactive process for the Eclipse treatment planning system. We describe AIO and present initial evaluation data.MethodsOur current institutional volumetric modulated arc therapy (RapidArc) planning approach for head and neck tumors places 3-4 adjustable OAR optimization objectives along the dose-volume histogram (DVH) curve that is displayed in the optimization window. AIO scans this window and uses color-coding to differentiate between the DVH-lines, allowing it to automatically adjust the location of the optimization objectives frequently and in a more consistent fashion. We compared RapidArc AIO plans (using 9 optimization objectives per OAR) with the clinical plans of 10 patients, and evaluated optimal AIO settings. AIO consistency was tested by replanning a single patient 5 times.ResultsAverage V95&V107 of the boost planning target volume (PTV) and V95 of the elective PTV differed by ≤0.5%, while average elective PTV V107 improved by 1.5%. Averaged over all patients, AIO reduced mean doses to individual salivary structures by 0.9-1.6Gy and provided mean dose reductions of 5.6Gy and 3.9Gy to the composite swallowing structures and oral cavity, respectively. Re-running AIO five times, resulted in the aforementioned parameters differing by less than 3%.ConclusionsUsing the same planning strategy as manually optimized head and neck plans, AIO can automate the interactive Eclipse treatment planning process and deliver dosimetric improvements over existing clinical plans.
Highlights
Intensity modulated radiotherapy treatment planning for sites with many different organs-at-risk (OAR) is complex and labor-intensive, making it hard to obtain consistent plan quality
PTVB and PTVE V95 values were marginally worse, consistently improved OAR sparing was obtained in the nominal automatic interactive optimizer solution (AIO) plan that used an objective-line distance (OLD) of 50 pixels, 9 optimization objectives per OAR, and a pause time T of 15 seconds
This increased OAR sparing using AIO came at the expensive of a 0.1% higher body-planning target volume (PTV) mean dose on average, while V5Gy, V30Gy and V50Gy were respectively 0.2%, 0.4% and 0.4% higher
Summary
Intensity modulated radiotherapy treatment planning for sites with many different organs-at-risk (OAR) is complex and labor-intensive, making it hard to obtain consistent plan quality. Radiotherapy treatments for head and neck cancer evolved from essentially contralateral parotid gland and spinal cord sparing [3] to include sparing of the ipsilateral parotid gland, the contralateral submandibular gland, multiple swallowing muscles and the oral cavity [4]. This further increases the difficulty of plan optimization and increases the likelihood that inconsistent planning results are obtained between planners. Automated planning is in its infancy, promising results have already been obtained using knowledge-based planning [5,6,7,8,9,10,11,12,13] and automated multicriteria plan optimization [14,15,16]
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