Analytic description of the image to patient torso registration problem in image guided interventions

Objective: The accurate registration of virtual pre-operative information of the human body anatomy, obtained as images with imaging devices, with real intra-operative information is one of the key aspects on which effective Image Guided Surgery (IGS) is based. The registration of pre-operative images on the real patient, during abdominal and thoracic  interventions, is influenced by many parameters, which in many cases are influenced each other, thus making it often difficult to define the problem and consequently to solve it for each specific kind of intervention. The objective of this paper is to obtain an analytic description of the 3D image to patient registration problem, which can be more intuitive than the traditional textual descriptions. Methods: The problem is formalized and various parameters affecting the registration are macro-classified in function of their nature. Results: The problem is analytically described discussing for each macro-category of parameters potential solutions to avoid or to reduce their contribution to the registration error. Conclusions: The availability of an analytic description of the image to patient torso registration problem can be beneficial for teaching IGS, to describe existing registration strategies, and to search new ones for each kind of surgery using a systematic approach.