Augmented reality-guided positioning system for radiotherapy patients

Abstract

In modern radiotherapy, error reduction in the patients' daily setup error is important for achieving accuracy. In our study, we proposed a new approach for the development of an assist system for the radiotherapy position setup by using augmented reality (AR). We aimed to improve the accuracy of the position setup of patients undergoing radiotherapy and to evaluate the error of the position setup of patients who were diagnosed with head and neck cancer, and that of patients diagnosed with chest and abdomen cancer. We acquired the patient's simulation CT data for the three-dimensional (3D) reconstruction of the external surface and organs. The AR tracking software detected the calibration module and loaded the 3D virtual model. The calibration module was aligned with the Linac isocenter by using room lasers. And then aligned the virtual cube with the calibration module to complete the calibration of the 3D virtual model and Linac isocenter. Then, the patient position setup was carried out, and point cloud registration was performed between the patient and the 3D virtual model, such the patient's posture was consistent with the 3D virtual model. Twenty patients diagnosed with head and neck cancer and 20 patients diagnosed with chest and abdomen cancer in the supine position setup were analyzed for the residual errors of the conventional laser and AR-guided position setup. Results show that for patients diagnosed with head and neck cancer, the difference between the two positioning methods was not statistically significant (P > 0.05). For patients diagnosed with chest and abdomen cancer, the residual errors of the two positioning methods in the superior and inferior direction and anterior and posterior direction were statistically significant (t = -5.80, -4.98, P < 0.05). The residual errors in the three rotation directions were statistically significant (t = -2.29 to -3.22, P < 0.05). The experimental results showed that the AR technology can effectively assist in the position setup of patients undergoing radiotherapy, significantly reduce the position setup errors in patients diagnosed with chest and abdomen cancer, and improve the accuracy of radiotherapy.

Keywords: augmented reality; position setup; position setup error; radiation therapy.

FIGURE 1

System layout

FIGURE 2

Isocentric calibration of the three‐dimensional (3D) virtual model (with breast patient as an example): (a) calibration module; (b) cross‐section of the human body, with the yellow arrow indicating the cross‐section of the virtual cube; (c) treatment couch side view. The calibration module is identified, and the 3D virtual model is loaded; (d) treatment couch side view. The contour distance between the calibration module and the virtual cube is d1, d2; (e) treatment couch side view. The virtual cube is aligned with the calibration module in all directions; (f) treatment couch side view. The calibration module is removed, and some normal tissues, planning target volume (PTV), and PTV (CTV), are displayed

FIGURE 3

AR position (ARPT) setup procedure (with breast patient as an example): (a) treatment couch side view. The initial position setup is carried out by the conventional laser method, and then the patient is adjusted according to the three‐dimensional (3D) virtual model displayed by AR; (b) treatment couch tail view. The initial position setup is carried out by the conventional laser method, and then the patient is adjusted according to the 3D virtual model displayed by AR; (c) treatment couch side view. The patient is consistent with the 3D virtual model in all directions; (d) treatment couch tail view. The patient is consistent with the 3D virtual model in all directions

FIGURE 4

Schematic diagram of bladder filling in abdomen patients: (a) schematic diagram of underfilling of the bladder; (b) schematic diagram of bladder overfilling; (c) schematic diagram of a well‐filled bladder

FIGURE 5

Comparison between the cone beam CT (CBCT) and simulation CT of the same two‐dimensional (2D) CT slice for planning target volume (PTV) in the AP, LR, and SI directions (with breast patient as an example). In the figure, the purple part is the simulation CT image, the green part is the CBCT image of the patient after position setup, and the PTV area is contoured with green lines. (a) AR positioning (ARPT) compared with simulation CT. (b) Laser position setup (LPT) compared with simulation CT