A method for estimating motion of an X-ray focal spot is provided. The acts of the method include acquiring image data by causing X-rays to be emitted from the X-ray focal spot of an X-ray source toward a radiation detector comprising multiple channels, wherein a subset of the channels each have a collimator blade positioned above the respective channel. The acts of the method also include independently estimating X-ray focal spot motion in an X-direction for the X-ray focal spot relative to an isocenter of the radiation detector and in a Y-direction along a direction of the X-rays for the X-ray focal spot relative to the isocenter based on respective channel gains for a first channel and a second channel of the subset of the channels.