Session Item

To present our clinical experience with an automated approach to IMRT treatment planning using expedited constrained hierarchical optimization (ECHO) to improve clinical workflow, planning efficiency, and plan quality and consistency.

After contouring, a template using multiple IMRT fields was created and sent to ECHO through the Eclipse® application program interface (API) plug-in. Institutional clinical criteria, including maximum and mean doses plus dose volume metrics, were separated into 2 categories: limits and guidelines. These clinical criteria were directly employed as template ECHO input parameters to derive appropriate objective functions and constraints. ECHO optimization strictly enforced limits as constraints and optimized the guidelines as much as possible using objective functions. The optimal fluence map generated by ECHO was imported automatically into Eclipse for leaf sequencing and final dose calculation. Upon ECHO completion, the planner received an email indicating the plan was ready for review. The email also includes a plan quality summary report. The plan was accepted by the planner if all clinical criteria were met, otherwise a limited number of parameters could be adjusted prior to another run with ECHO. 

We have established a process to develop and implement ECHO to the clinic. For each disease site, a template based on the established clinical criteria (limit and guidelines) was created and ECHO only required limited representative training patient data to fine tune few optimization parameters (e.g., dose fall-off criteria, slip factors). After training, the same parameters were then used to validation study of slightly more plans with a few prescription schemes and corresponding clinical criteria and compared with manual plans. Those parameter templates were then clinically implemented to plan that disease site with widely different prescription scheme and can easily adapt to changing clinical practice. Table 1 illustrates details of the process.

From 4/2017 to 2/2021, 3401 patients underwent radiotherapy using 3896 ECHO produced plans. Figure below shows treated ECHO plans for different disease sites. PTV sizes varied greatly with median 77 cc (range 1.5 - 988). The median time to produce one ECHO plan was 29 minutes (range 7 - 168) mainly depending on the PTV size. For prostate plans, all plans were clinically accepted after single run. For paraspinal/metastatic tumor SBRT plans, 76% of ECHO plans required only one run.

An automated and clinical-criteria-driven optimal planning has been established in our institution. ECHO now produces a majority of SBRT plans for paraspinal and other metastatic tumors in our clinic. We are rapidly expanding ECHO for prostate, non-small-cell lung cancer and other disease sites. ECHO improved consistency of plan quality for treatment planning and enabled expedited treatment including same day SBRT treatment in our clinic.