Co-registration of Positron Emission Mammography (PEM) images and X-ray mammograms

Accurate co-registration of metabolic and X-ray images of the breast is important when acquiring information about the location and diagnosis of suspicious lesions or tumours. X-ray mammograms reveal abnormal tissue densities, while metabolic images identify regions of abnormal metabolism. Conventional nuclear medicine and radiologic breast images must be acquired at different times with different patient positions making co-registration difficult. Positron Emission Mammography (PEM) simplifies the image registration process by acquiring both an X-ray density image and a metabolic image consecutively, without moving the patient between scans. The authors have integrated PEM detectors into a conventional mammographic unit and they have developed a co-registration tool. The tool is a thin sheet of plexiglass (130×95×3 mm³) with a 49×39 mm² window. The tool protrudes from the side of the upper PEM detector. The suspicious area of the breast is imaged through this tool during a magnified X-ray mammogram, producing a radiolucent region on the resulting film image. During a positron emission scan, detectors acquire an image of the same region. The PEM detectors can be positioned anywhere along the width of the breast to provide a complete scan