Computer Vision News - April 2021

Medical Imaging Projects 12 When planning many orthopedic procedures, a computerized tomography (CT) scan is taken in advance in order to get clear and accurate three-dimensional visualization of the bones. This three- dimensional bone model assists the orthopedic surgeon in non-invasive decision making and planning of the surgical procedure. Accurate visualization is particularly essential in arthroplasty procedures (joint replacement), such as knee, hip, or shoulder replacement surgeries, as well as intricate spinal procedures. The modelling processes involves segmentation of the joint bones, osteophytes (bone spurs) and various anatomical landmarks. The resulting high-resolution model is crucial for accurately planning and designing the shape, size, location, and placement of the new implant. One of the most common problems in bone segmentation occurs when a CT scan includes the presence of metals in the bones. These metals appear in CT scans when a patient has undergone either previous orthopedic procedures (such as hip or knee replacements) or previous surgical corrections after traumatic Metal Implant Segmentation for Arthroplasty injuries (such as spinal fusions). In these cases, the CT images become limited and challenging because the metallic presence creates “glare” (or streak) artifacts which blur and distort the image and complicate the bone segmentation process. These artifacts appear in the scan as bright and dark high intensity streaks that originate from the metal object and often block the surrounding anatomical structures and prevent accurate image processing. In other words, the presence of high intensity metal objects in CT scans produces an "aura" around them which obscures valuable information about the surrounding anatomy. A knee CT scan in the presence of metal. The star-shape streak artifact (“aura”) can be seen originating from the metal implant on the top.