Knowledge Models as Teaching Aid for Training Intensity Modulated Radiation Therapy Planning: A Lung Cancer Case Study

Abstract

Purpose: Artificial intelligence (AI) employs knowledge models that often behave as a black-box to the majority of users and are not designed to improve the skill level of users. In this study, we aim to demonstrate the feasibility that AI can serve as an effective teaching aid to train individuals to develop optimal intensity modulated radiation therapy (IMRT) plans. Methods and Materials: The training program is composed of a host of training cases and a tutoring system that consists of a front-end visualization module powered by knowledge models and a scoring system. The current tutoring system includes a beam angle prediction model and a dose-volume histogram (DVH) prediction model. The scoring system consists of physician chosen criteria for clinical plan evaluation as well as specially designed criteria for learning guidance. The training program includes six lung/mediastinum IMRT patients: one benchmark case and five training cases. A plan for the benchmark case is completed by each trainee entirely independently pre- and post-training. Five training cases cover a wide spectrum of complexity from easy (2), intermediate (1) to hard (2). Five trainees completed the training program with the help of one trainer. Plans designed by the trainees were evaluated by both the scoring system and a radiation oncologist to quantify planning quality. Results: For the benchmark case, trainees scored an average of 21.6% of the total max points pre-training and improved to an average of 51.8% post-training. In comparison, the benchmark case's clinical plans score an average of 54.1% of the total max points. Two of the five trainees' post-training plans on the benchmark case were rated as comparable to the clinically delivered plans by the physician and all five were noticeably improved by the physician's standards. The total training time for each trainee ranged between 9 and 12 h. Conclusion: This first attempt at a knowledge model based training program brought unexperienced planners to a level close to experienced planners in fewer than 2 days. The proposed tutoring system can serve as an important component in an AI ecosystem that will enable clinical practitioners to effectively and confidently use KBP.

Keywords: intensity modulated radiation therapy; knowledge model; lung cancer; machine learning; tutoring system.

Figure 1

System design diagram for the training program which includes a tutoring system at its core and a host of training cases. The tutoring system brings together the trainee, trainer, and the TPS. A trainer is optional for assisting the interaction between the trainee and the tutoring system. The tutoring system is powered by a scoring system and a set of knowledge models.

Figure 2

Interactive user interface of the tutoring system. Within the system, the trainee is capable of checking the current plan's metrics against the clinical plan and knowledge model DVH prediction.

Figure 3

Screenshot of the benchmark case in (a) axial, (b) coronal, and (c) sagittal view. The clinically delivered plan's isodose is displayed.

Figure 4

Training diagram that is largely based on comparison between trainee's results and knowledge-based planning (KBP) models. Blue-colored process is geometry-based assessment. Red-colored process is objective-based assessment. Green-colored process is geometry and objective based assessment. Dashed box is considered optional step. Cylindrical block is based on knowledge-based model.

Figure 5

(A) For each trainee (column), the total score for the benchmark case: pre-training plan (purple dot) and post-training plan (green dot) compared to the clinically delivered plan (black line). (B) For each training case (column), and for each trainee (color dots), the score difference between the trainee plan and the clinically delivered plan (black line indicating 0).