Example methods and systems are provided to perform radiation dose estimation for a target object. In one example, radiation dose estimation may include obtaining projection image data acquired using an imaging system, generating partially reconstructed volume image data based on the projection image data, and generating a partition of the projection image data. The partially reconstructed volume image data may be associated with a first region of a total radiation field. The partition may be associated with a second region of the total radiation field that is located before the first region from a direction of a radiation source. Radiation dose data may be estimated for the target object based on the partially reconstructed volume image data associated with the first region and the partition associated with the second region.