[Frameless registration for chest SPECT and X-ray CT image by volume matching]

Image registration of functional (SPECT) and morphological (X-ray CT/MRI) images has been studied in order to improve the accuracy and the quality of the image diagnosis. This paper describes a new registration method for chest SPECT and X-ray CT images. Presented method is a frameless and automatic registration method which calculates a transformation matrix between two coordinate systems of image data by an optimization method. This registration method uses similar physical characteristics of X-ray CT and transmission CT image. The three-dimensional overlap of the body region is used for image matching. Precision evaluation and visual image evaluation were conducted. The result of the precision evaluation with a phantom and clinical data suggested the clinically acceptable robustness in registration procedure. Visual evaluation of registered images confirmed the usefulness of this method in clinical applications.