Integration of tomographic angiograms into neurosurgical navigation should decrease the probability of vascular injury and allow localization of vascular lesions. Information from angiograms is often presented using maximum intensity projections (MIPs), which provide a more intuitive presentation of 3D vascular structures. Conventional MIPs involve the whole image volume during ray casting. Our goal was to construct surgically appropriate MIPs that excluded information contralateral to the operation site and to quantify the accuracy of vessel depiction using this new method. For each angiogram slice, the center of mass (COM) was calculated. Together, the COM coordinates formed a boundary plane that clipped the contralateral information from ray casting. A separate depth buffer was created to preserve 3D information. MIPs were examined quantitatively using a mathematical model of the head containing vascular structures of known diameter. The vessel widths of the resulting MIPs were then measured and compared. To examine the spatial accuracy of MIP images, a vascular phantom was created, which had rigid vessels of known diameter and extrinsic fiducial markers to perform a physical to image space registration. Studies with the mathematical model showed that the vessels appeared smaller in MIPs than their actual diameters. This decrease is attributed to the statistical properties of the ray casting process that are affected by the pathlength. Studies with the vascular phantom show correct localization of the probe in tomographic and projective image space. From these studies, we concluded that additional methods for providing information concerning vessel proximity during surgical guidance should be investigated. Surgically appropriate MIPs provide comparable images to conventional MIPs; however, they allow more focus on the vascular structures in proximity to the target site.
During a typical image-guided neurosurgery procedure, the surgeon used anatomical information from tomographic image sets to help guide the surgery. These images provide high- level details of the patient's anatomy. The images do not, however, provide the surgeon with information regarding brain function. The identification of cortical function in addition to the display of tomographic images during surgery would allow the surgeon to visualize critical areas of the anatomy. This would be beneficial during surgical planning and procedures by identifying eloquent cortical regions (such as speech, sensory, and motor areas) that should be avoided. We have designed and implemented a system for recording and displaying cortical brain function during image-guided surgery. Brain function is determined using an optically tracked cortical stimulator. The image-space location of each stimulation event is recorded, and the user has the ability to label this location according to function type. Functional data can be displayed on both tomographic and rendered images. Tracking accuracy of the cortical stimulator has been determined by comparing its position to that of a tracked surgical probe with known localizing accuracy.
Longitudinal magnetic resonance spectroscopy (MRS) studies require accurate repositioning of the volume of interest (VOI) over which measurements are made. In this work we present and evaluate a method for the image-guided repositioning of brain volumes of interest. The point-based registration technique we developed allows the repositioning to be performed on-line (i.e., while the patient is in the scanner). MR image volumes were acquired from six subjects, three scans each over the course of a month. During the first scan, two spectroscopy VOIs are visually selected: one in the frontal white matter, the other in the superior cerebellar vermis. The coordinates of 13 internal brain landmarks were also identified. During both subsequent scans, the same 13 landmarks were also identified, and the transformation that registers the first set of landmarks to the subsequent set is compared. This result is used to automatically map the position of the spectroscopy. VOIs from the first volume to the current volume. For the six subjects evaluated to date, we show an average repositioning error of the spectroscopy VOIs in the order of 1 mm. This accuracy allows us to conclude that any variation in the MR spectra are unlikely to be due to repositioning error.
Conference Committee Involvement (10)
Image-Guided Procedures, Robotic Interventions, and Modeling
18 February 2014 | San Diego, California, United States
Image-Guided Procedures, Robotic Interventions, and Modeling
12 February 2013 | Lake Buena Vista (Orlando Area), Florida, United States
Image-Guided Procedures, Robotic Interventions, and Modeling
5 February 2012 | San Diego, California, United States
Visualization, Image-Guided Procedures, and Modeling
13 February 2011 | Lake Buena Vista (Orlando), Florida, United States
Visualization, Image-Guided Procedures, and Modeling
14 February 2010 | San Diego, California, United States
Visualization, Image-guided Procedures and Modeling
8 February 2009 | Lake Buena Vista (Orlando Area), Florida, United States
Visualization, Image-Guided Procedures, and Modeling
17 February 2008 | San Diego, California, United States
Visualization and Image-Guided Procedures
18 February 2007 | San Diego, CA, United States
Visualization, Image-Guided Procedures, and Display
12 February 2006 | San Diego, California, United States
Visualization, Image-Guided Procedures, and Display
13 February 2005 | San Diego, California, United States
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