A method for a computer system to perform adaptive radiotherapy treatment planning comprises: obtaining treatment image data associated with a first imaging modality, wherein the treatment image data is acquired during a treatment phase of a patient； obtaining planning image data associated with a second imaging modality, wherein the planning image data is acquired prior to the treatment phase to generate a treatment plan for the patient； determining whether a difference between the treatment image data and the planning image data exceeds a threshold；in response to determination that the difference exceeds the threshold,transforming the treatment image data associated with the first imaging modality to generate transformed image data associated with the second imaging modality； andprocessing, using a first deep learning engine, the transformed image data to generate output data for updating the treatment plan；otherwise, processing, using a second deep learning engine, the treatment image data and the planning image data to generate output data for updating the treatment plan.
