ABSTRACT
The majority of the chapters of this book discuss methods for rigid-body registration and applications (especially of the brain in the closed skull) where these methods can be used for intermodality, intramodality, or image to physical space registration. There is increasing interest now in nonrigid registration, which is more generally applicable. Chapter 13 reviewed the main approaches to nonrigid registration. These methods are almost invariably used for intramodality registration of images from the same or different subjects. Chapter 14 discusses the intersubject registration of brain images in detail. For image-to-physical registration, as used for image-guided surgery and also for intermodality applications, nonrigid registration is a harder problem
because of the difference in the information available in the spaces being aligned. In these cases, biomechanical models of the sort described in this chapter have the potential to provide model-based registration techniques that can align an image collected on one occasion with a very different image or the coordinates of a surgical instrument at a later time. These models can take into account the mechanical properties of the tissue, the operative conditions, and the presence of surgical instruments such as retractors. Furthermore, sparse intraoperative information, such as photographs of the site of resection or ultrasound images, can be used as constraints on the models to improve accuracy.
