Abstract: A method and system of rapidly detecting and mapping a plurality of marker points identified in a sequence of projection images to a physical marker placed on a patient or other scanned object. Embodiments of the invention allow a marker physical mapping module executable by an electronic processing unit to obtain a sequence of images based on image data generated by a scanner. Each image in the sequence of images represents an angle of rotation by the scanner and includes a plurality of marker points each having a U position and a V position. Expected U and V positions for the physical marker are calculated and a list of candidate marker points is created based on the expected positions. The images are processed and selected candidate marker points are added to a good point list.

Abstract: A method and system of determining a radial distance (R), an angular position (?), and a axial position (Z) of a marker identified in a sequence of projection images. Embodiments of the invention allow a marker three-dimensional localization module executable by the electronic processing unit to obtain a sequence of images based on image data generated by a scanner. Each image in the sequence of images represents an angle of rotation by the scanner and includes a marker point position. The behavior of first values and second values of the marker point positions are analyzed through the sequence of images to determine the radial distance of the marker, the angular position of the marker, and the axial position of the marker. Thus, embodiments of the invention allow for rapidly detecting and localizing external markers placed on a patient in projection images.

Abstract: A mechanism for rapidly detecting and localizing external markers placed on a patient in projection images. Embodiments of the invention allow the markers to be detected even in the presence of dense surrounding anatomy and extensive patient motion. Once the positions of the marker points on the projection images are extracted, the marker points can be used to perform marker-based patient motion detection. Embodiments of the invention can also be used outside of motion correction, such as for scanner calibration, automatic cephalometric measurements, and quality control assessment.

Abstract: A method and a system for determining patient motion in an image. The method includes obtaining an image based on image data generated by a scanner during a scan. The image includes at least three markers assumed to be in a rigid or semi-rigid configuration. Each of the at least three markers has actual measured positions on a detector panel of the scanner in a first dimension and a second dimension. The method further includes determining a reference three-dimensional position for each of the at least three markers and defining equations describing the relationship between the reference three-dimensional position and the actual measured positions of each of the at least three markers, geometric parameters of the scanner, and patient motion.

Abstract: A method of mapping eddy currents in magnetic resonance imaging apparatus of the type having gradient coils and RF coils, the method including the steps of (a) applying a pulse sequence to the apparatus in a first excitation stage, including the steps of applying a first test gradient of a first polarity by the gradient coils; subsequently applying a first RF pulse of the first polarity by the RF coils; subsequently applying at least one first imaging gradient by the gradient coils; (b) measuring a first output signal in the first stage in response to the RF excitation pulse and the gradients; (c) subsequently applying a pulse sequence to the apparatus in a second excitation stage, including the steps of subsequently applying a second test gradient of a second polarity opposite to the first polarity by the gradient coils; subsequently applying a second RF pulse of the second polarity; subsequently applying at least one second imaging gradient by the gradient coils; (d) measuring a second output signal in the