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A Patient Population Based Approach for Disease Site Specific Intensity-Modulated Radiation Therapy (IMRT) Treatment Planning

H Zhang

H Zhang1*, D Stanojevic1, R Meyer2, W D'Souza1, (1) University of Maryland School of Medicine, Baltimore, MD, (2) University of Wisconsin, Madison, WI

SU-E-T-642 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To develop and evaluate a population based planning scheme for disease site specific IMRT treatment planning.

Methods: A database of previously treated locally advanced head and neck patients from our institution was retrospectively used for this study. The treatment targets involved primary tumor, high risk and low risk nodal volumes. Organs-at-risk (OARs) included both parotids, oral cavity, brain stem and the spinal cord. Nine-beam IMRT plans were generated using the Pinnacle3 planning system for 80% of patients. These plans served as the population basis. Thousands of apertures from these cases were extracted. From these apertures, prospective case-specific apertures were either selected from the population basis or derived using machine learning for each of the remaining 20% of the patients. Aperture-based 3D dose distributions were calculated in parallel using Monte Carlo-based Kernel Superposition (MCKS) via a high throughput computing environment. Aperture weights of each case were optimized via an in-house developed progressive dose optimization (PDO) approach. The PDO approach involved solving the DO problem by dividing the problem into sub-problems, each of which was solved while maintaining a global view of the full problem. Our approach was compared with conventional IMRT and two-arc volumetric modulated arc therapy (VMAT).

Results: On average, the improvements achieved using population approach in parotid gland mean dose were 16% and 15%, in the maximum dose to the spinal cord were 21% and 28%, in mean oral cavity dose were 10% and 24% and in maximum brain stem dose were 6% and 15% compared with conventional IMRT and two-arc VMAT. t-test showed that these improvements were significant (p < 0.001). Dose homogeneity for all PTVs (tumor and nodes) was higher for population based approach as well.

Conclusion: Population based planning approach resulted in superior plan quality compared with conventional IMRT and VMAT.

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