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Use of preoperative and intraoperative magnetic resonance tractography in intracranial tumor surgery.

The goals of every modern neurosurgeon during surgery for intracranial tumors can be summarized as follows: 1) a small and less invasive craniotomy; 2) a resection as wide as possible; 3) the preservation of eloquent areas and white matter major tracts (WMMTs); and 4) the minimization of postoperative morbidity. The development of image-guided neurosurgery improved the microsurgical treatment of brain tumors, of vascular malformations, and of other intracranial lesions. The dynamic changes of intracranial contents regularly occurring during the surgical procedures (the so-called brain shift) sometimes invalidates the preoperative surgical planning and, therefore, only intraoperatively acquired images allow us to perform what is the closest to real intraoperative image-guided neurosurgery presently available. Magnetic resonance imaging (MRI) currently represents the more elegant imaging method for intraoperative image guidance, mainly because of excellent imaging qualities and avoidance of ionizing radiations.5,9–11 The development and clinical application of intraoperative MRI passed through 1) low to very low field systems; 2) midfield systems; and 3) high-field systems. The major advantages of high-field intraoperative MRI are: 1) acquisition of high-quality images; 2) functional capabilities (magnetic resonance spectroscopy, functional MRI, magnetic resonance angiography, chemical shift imaging, diffusionweighted images, and more); and 3) updates of data outside the magnet at any time by using neuronavigation systems.5,9–12 The latest concept of intraoperative high-field MRI has been developed by a cooperation of Siemens and BrainLab companies and is the so-called BrainSuite. BrainSuite (Fig. 21.1) is an operative theater with 1.5-T MRI (Siemens, Erlangen, Germany) integrated with a neuronavigation system, a microscope tracked with navigation software, and digitized image transfer (BrainLab, New York, NY). In this room, the patient is placed on a rotating operating table. During surgery, the head and the operative area are placed outside the 5 Gauss line. For this reason, surgical procedures can be performed with standard neurosurgical instruments and microscope. At any time during the operation, the surgical procedure can be interrupted and the patient can be placed into the magnet by simple rotation of the table. The BrainSuite was installed for the first time in Europe in the Department of Neurosurgery of the University of Roma “La Sapienza”–Sant’Andrea Hospital during 2004. The advantages of high-field intraoperative MRI and the BrainSuite concept can be summarized as follows: 1) highquality images, including angio-magnetic resonance sequences; 2) use of standard surgical instruments; 3) integration with a neuronavigational system and possibility of image update at any moment; and 4) functional images: a) spectroscopy, b) diffusion and diffusion tensor imaging (DTI), and c) fiber tracking.