A multiple model approach to respiratory motion prediction for real-time IGRT

Abstract

Respiration induces significant movement of tumours in the vicinity of thoracic and abdominal structures. Real-time image-guided radiotherapy (IGRT) aims to adapt radiation delivery to tumour motion during irradiation. One of the main problems for achieving this objective is the presence of time lag between the acquisition of tumour position and the radiation delivery. Such time lag causes significant beam positioning errors and affects the dose coverage. A method to solve this problem is to employ an algorithm that is able to predict future tumour positions from available tumour position measurements. This paper presents a multiple model approach to respiratory-induced tumour motion prediction using the interacting multiple model (IMM) filter. A combination of two models, constant velocity (CV) and constant acceleration (CA), is used to capture respiratory-induced tumour motion. A Kalman filter is designed for each of the local models and the IMM filter is applied to combine the predictions of these Kalman filters for obtaining the predicted tumour position. The IMM filter, likewise the Kalman filter, is a recursive algorithm that is suitable for real-time applications. In addition, this paper proposes a confidence interval (CI) criterion to evaluate the performance of tumour motion prediction algorithms for IGRT. The proposed CI criterion provides a relevant measure for the prediction performance in terms of clinical applications and can be used to specify the margin to accommodate prediction errors. The prediction performance of the IMM filter has been evaluated using 110 traces of 4-minute free-breathing motion collected from 24 lung-cancer patients. The simulation study was carried out for prediction time 0.1-0.6 s with sampling rates 3, 5 and 10 Hz. It was found that the prediction of the IMM filter was consistently better than the prediction of the Kalman filter with the CV or CA model. There was no significant difference of prediction errors for the sampling rates 5 and 10 Hz. For these sampling rates, the errors of the IMM filter for 0.4 s prediction time were less than 2.1 mm in terms of the 95% CI criterion or 1.1 mm in terms of the standard deviation (SD) or root mean squared errors (RMSE) criterion. For the prediction time of 0.6 s the errors were less than 3.6 mm in terms of the 95% CI criterion or 1.8 mm in terms of the SD/RMSE criterion. The prediction error analysis showed that the average percentage of the target lies outside the 95% CI margin was 5.2% and outside the SD/RMSE margin was 24.3%. This indicates the effectiveness of the 95% CI criterion as a margining strategy to accommodate prediction errors.

Imaging the Lung in Radiotherapy: Where 4D Meets Multimodality

“…This characterization serves two purposes. First, in the 4D treatment (76–78), due to the finite hardware latency, it is desirable to predict the tumour motion for a short period of time, in order to proactively adjust the treatment for any deviation of the tumour motion from the original plan (79–82). Second, the complexity of respiratory motion is being further explored by separating the random perturbation from the regular periodic breathing motion (83, 84), as the regular component is well modelled and planned for; and the random perturbation is generally in the low‐frequency domain that is easier to predict for a short period.…”

Improved Detection of Human Respiration Using Data Fusion Basedon a Multistatic UWB Radar

“…To apply the above equations for human respiration detection, a proper dynamic model should be first designed to describe the breathing process of human targets. Several models have been proposed for the purpose, i.e., the constant velocity (CV) model, the constant acceleration model (CA), and the interacting multiple model (IMM) [26]. Due to having no need of precisely predicting the respiratorymotion, the simple CV model was used in this paper.…”

Simulation and Experimental Studies of Real-Time Motion Compensation Using an Articulated Robotic Manipulator System

“…In recent years, more advanced techniques for radiation therapy, such as stereotactic body radiation therapy (SBRT) and image-guided radiotherapy (IGRT), require to be delivered with even greater accuracy. Kalman filter, [6][7][8] artificial neutral networks, 6,9) probabilistic approaches, 10) the autoregressive moving average model, 11) the multi-step linear method, 12) and wavelet-based multiscale autoregression. 13 14) However, the Stewart platform couch itself has physical limits on its motion, corresponding to 3~4 cm in each of the three physical dimensions; once a limit is reached, the couch simply cannot move any further, even though it is enough to cover the organ movement.…”