Origins of intraoperative MRI

Abstract

Neurosurgical diagnosis and intervention has evolved through improved neuroimaging, allowing better visualization of anatomy and pathology. This article discusses the various systems that have been designed over the last decade to meet the requirements of neurosurgical patients and opines on the potential future developments in the technology and application of intraoperative MRI. Because the greatest amount of experience with intraoperative MRI comes from its use in brain tumor resection, this article focuses on the origins of intraoperative MRI in relation to this field.

Fig. 1

Brain shift. (A) T1-weighted axial MRI before craniotomy. (B) Same axial plane MRI after craniotomy performed. (C) MRI after lesion resection. Note the significant shift of intracranial contents after craniotomy, cerebrospinal fluid drainage, and lesion resection.

Fig. 2

The MRT unit at BWH. The General Electric Signa 0.5T iMRI is an open-configuration “double donut” system that allows the surgeon to operate between each superconductive magnet coil (pictured).

Fig. 3

Intraoperative colocalization using iMRI images and 3-D Slicer software. (A) Tumor, functional MRI, and diffusion tensor imaging are colocalized with standard MRI. (B) After craniotomy is performed, 3-D Slicer compensates for brain shift, allowing surgeons to visualize not only shift of gross neuroanatomy but also functional regions and white matter tracts.

Fig. 4

The PoleStar iMRI. The open-bore configuration PoleStar N-20, despite its low-field 0.15T magnet, has allowed many institutions to take advantage of iMRI without completely remodeling their operative suite to accommodate a larger, high-field stationary iMRI. The Polestar is compact enough to be stored in a shielded room (pictured on the right side of the figure) when not in use. If a smaller room cannot be dedicated to storage, an in-suite “hangar” can be set up to shield the magnet when not in use. (Courtesy of Medtronic Navigation, Louisville, CO; with permission.)

Fig. 5

The IMRIS iMRI. The IMRIS iMRI suite features a high-field, closed-bore magnet. (A) The IMRIS magnet in its storage room, shielding doors opened to show its relation to the operative suite when not in use. (B) The magnet has moved on its ceiling-mounted rails to its position over the region of the patient's head. The 1.5-T magnet can be brought from its park position in the storage room to a fully operational position within the operating room in less than 90 seconds, allowing for efficient scanning while still remaining unobtrusive. (C) An example of the IMRIS magnet serving two separate operating rooms. (The magnet can swivel 180° in the storage room to orient the working end toward the appropriate operating room.) (Courtesy of IMRIS, Inc., Winninpeg, Manitoba, Canada.)

Fig. 6

The NeuroArm MRI-compatible neurosurgical robot. (A) Detailed picture of one of the NeuroArm's two operative limbs, with bipolar cautery attachment. (B) Command center for NeuroArm robot, where surgeon is seated and driving the movements of the robot through haptic-feedback controllers. (C) Real-time virtual reality display of the robot's position is delivered to the surgeon. Other virtual reality displays feature colocalization of MRI, functional MRI, and diffusion tensor imaging. (Courtesy of NeuroArm, Calgary, Alberta, Canada.)

Fig. 7

The Advanced Multimodality Image Guided Operative (AMIGO) suite at the National Center for Image Guided Therapy, BWH and the Harvard Medical School. In AMIGO, real-time anatomic imaging modalities such as radiography and ultrasound are combined with the cross-sectional digital imaging systems of PET-CT and MRI. (A, B) Cross-sectional and oblique views of the three-room suite composed of a PET-CT (left room), state-of-the-art operating room, and 3.0T MRI (right room). (Courtesy of GE Healthcare, Wauwatosa, WI; with permission.)