Intraoperative ultrasound (US) in image-guided surgery (IGS)
Intra-operative imaging has been dominated by fluoroscopy for many years, followed more recently by mobile computed tomography (CT) platforms. However, both modalities make radiation exposure a concern for patients and surgeons alike. In the last several years, magnetic resonance imaging (MRI) has been finding its way into the operating room (OR), making high-contrast soft-tissue details available during surgery, but the size of these MRI machines makes them bulky for use in an already crowded OR. Moreover, MRI still remains far more expensive, severely restricting its use. Although ultrasound has established itself as an important imaging method for applications like obstetrics and breast imaging, its use as a guidance tool has been fairly limited in the past. Compared with other modalities, ultrasound yields images that are lower in quality for surgical guidance. Also ultrasound lacks of registration coordinates, owing to the freehand nature of ultrasound image acquisition. However, digital beam formers and harmonic imaging have greatly improved ultrasound image quality. Extensive research is being conducted to tackle the speckle that plagues ultrasound images. Motorized transducers for volume data acquisition and advanced rendering algorithms have made 3-D ultrasound a reality. New motion tracking system has been made available in the OR. These advances, combined with the inherent safety and real- time nature of ultrasound, indicate that ultrasound could be a viable modality for surgical navigation. Up till now, ultrasound guidance has been successfully used for areas like breast biopsies and other tissue aspiration for almost a decade. More recently, ultrasound- guided injections have proved effective for treating musculoskeletal conditions like injured tendons, ligaments, and joints. Intravascular ultrasound is also becoming valuable in stent placements. By visualizing stents in real time, surgeons can position them precisely, thereby reducing occurrence of restenosis. With the advent of portable handheld equipment that lends itself to the space limitations within the OR, ultrasound is even more attractive for intra-operative use.
- Ultrasound based image-guided surgery system
- Image registration for ultrasound images