Mathematical Navigation in Surgery of Brain Tumors

B.P. Fadeev

Municipal Multi-Field Hospital N 22, Saint Petersburg, Russia

 

Efficacy of brain tumors treatment, rehabilitation duration depends on microsurgical technique with minimum traumatic lesion of soft tissue and skull bones, cortex and cerebral substance adjacent to a tumor, pial and major vessels. It can be achieved by tumor visualization with the help of MRI and determining an approach direction, i.e. a trephination area and a zone of the cortex dissection. A calculation goal is choosing the shortest way to a tumor with preservation of eloquent zones. Use of markers and repeated CT is time-consuming and lacks precision; surgical navigators are expensive.

Computer processing of MRI data was used: scanning of three projections of the most informative tomograms, printing of magnified images, comparison of indices of the MRI scale ruler with an image and transfer of obtained linear dimensions on a surface of a patient's head. The curves were measured with the help of a curvimeter. Reference points were as follows: the sagittal sinus, occipital eminence and nose bridge. A tumor size was measured, then location of MCA branches, draining veins and central gyri was determined more precisely. The obtained points were plotted on a head skin. It was done for tracing areas both of incision of soft tissues and trephination.

A size of a trephination window was calculated on the basis of the following parameters: a) tumor transverse dimensions; b) thickness of soft tissues and skull bones, which limits changing a lateral position of an instrument; c) a distance between the cortex and a tumor distal surface. A length of encephalotomy was conditioned by a size and number of instruments, necessary for manipulations within a cerebral wound. A size of a trephination window in tumors, growing into the cortex, was dependent on an area of changes, watched in MRI-images.

This method of calculating a place and direction of an approach to brain tumors, as well as a size of a trephination window and a length of encephalotomy is carried out before operation with the help of a computer and mathematical analysis of tomograms and does not demand expensive technical support. A minimum error of calculations allows to make operations less traumatic and to reduce a term of postoperative rehabilitation.