A quantitative measure for radiation treatment plan quality

Purpose: To develop and validate an intensity modulated radiation therapy (IMRT) treatment plan quantitative score using QUANTEC dose/volume parameters to assess plan quality. Methods: 132 IMRT and volumetric modulated Arc therapy (VMAT) patient plans of various treatment sites were evaluated. The optimized plan’s dose volume histogram (DVH) was exported to Velocity for evaluation. The proposed scoring was based on calculating the shortest distance from the QUANTEC objective to the DVH line of each organ. Each plan was normalized against the ideal plan where the organs at risk (OARs) received no dose and hence the distance between the QUANTEC objective and the DVH line was maximized. These normalized scores enabled the comparison of the quality of plans across treatment sites and dosimetrists. The scores were plotted and statistically analyzed to serve as a basis for future research. Results: The score for each treatment site was evaluated and the average percentage scores±SD were found to be 43.5 ± 21.0, 33.3 ± 31.7, 42.6 ± 23.3, 40.2 ± 24.4, 33.5 ± 23.5 for the sites of abdomen, brain, chest, head/neck, and pelvis respectively. Differences in scores between the treatment sites were largely attributed to OAR segmentation and proximity of the OAR to the planning target volume (PTV). Small score differences between dosimetrists were attributed to the number of plans they have completed. Conclusion: This approach allows comparison of patient treatments which will help improve patient care and treatment outcomes. A larger sample of treatment plans is being evaluated to investigate the effect of dosimetrist’s experience on plan quality.