A Method for Real-Time Patient Positioning Verification in Radiotherapy Using Multi-Angular Images with Conventional Video Cameras

Background: Accurate patient positioning and the corresponding position verification play a key role in precision radiotherapy. The conventional position verification techniques, such as cone-beam computed tomography (CBCT), used in radiotherapy deliver additional radiation doses to patients; thus some complications may occur in the surrounding normal tissue. Additionally, the present registration and fusion algorithms require a long time to verify and monitor the patient's position in real-time. Method: A new simple method using three conventional video cameras from different directions for observing the changes in the patient's position and taking the multiangular surface images of the patient without delivering additional doses of radiation is proposed in this paper. Real-time patient position verification could be achieved through this Oriented FAST and Rotated BRIEF (ORB) algorithm modified by us. Results: A plastic patient model immobilized with thermoplastic shell on a simulation couch was used to verify the accuracy and feasibility of our method. Testing results showed that the position and angle offset errors identified with our system were less than 1 mm and 1°, respectively. Moreover, the modified ORB algorithm was fast enough for real-time images comparison. Conclusion: This proposed method shows a great potential for application in verifying and monitoring the patient's position in real time during radiotherapy.