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Intra-operative Imaging Techniques During Surgical Management of Gliomas


Figure 5: Resection of a Glioma that Has Been Labeled with 5-Aminolevulinic Acid


Figure 6: Functional Magnetic Resonance Imaging of Motor and Pre-motor Areas


Under the fluorescent lighting of the operating microscope, the malignant tissue is centrally located and glowing with an apparent deep pink color.


Figure 7: Diffusion Tensor Imaging Tractography in a Patient with Glioma


Intra-operative direct cortical mapping results are overlaid on the 3D volume. The motor region defined by functional magnetic resonance imaging (fMRI) is more extensive than that defined by direct cortical mapping; this lack of specificity makes fMRI unsuitable for the intra-operative identification of eloquent cortical regions.


Figure 8: Example Magnetoencephalograph of Somatosensory Stimuli to the Right Lip and Right Index Finger


Magnetic Field Response to a Tactile Stimulus fT 0.0000s 0.0060s 0.0120s 0.0180s 0.0240s 0.0300s 0.0360s 0.0420s 0.0480s 0.0540s


382 355 328 300 273 246 218 191 164 136 109 82 54 27 0


0.0600s 0.0660s 0.0720s 0.0780s 0.0840s 0.0900s fT 200


-200 0


-0.1 0.0 0.1 0.2


Multiple stimulus trials are performed for each site and cortical magnetic fields are recorded. The trials are averaged and a single dipole is reconstructed for each site using the least-square fit method. The resulting dipoles are then displayed on a co-registered, T1-weighted post-gadolinium coronal magnetic resonance slice. RD2 = right index finger; RLip = right lip.


The regions highlighted in orange correspond to descending corticospinal fiber tracts. The tractography has been integrated with a neuronavigational system for intra-operative use.


MRI and intra-operative ultrasound (IUS) are being developed to address these issues.


Intra-operative Magnetic Resonance Imaging As its name suggests, intra-operative MRI refers to the acquisition of the MRI using a specialized scanner in the operating room itself.12


require that the surgical suite be designed for rapid, easy transport of the patient to the scanner for image acquisition, such as with a motorized table that is continuous with the bore of the scanner. Low-field scanners usually function at or below 0.5T and are less expensive than the high-field scanners (see Figure 3). Although these images are of lower resolution, the machines are smaller and may thus be moved over a stationary patient.13


High-field


intra-operative MRI usually functions at 1.5T or greater and yields high-resolution scans (see Figure 2). These units are bigger and often


US NEUROLOGY


Intra-operative MRI can confer great advantages in glioma surgery.14,15 First, it allows for the most accurate navigational co-registration because the scan is performed after the patient has been positioned for surgery. Fiducial markers are unnecessary and only the external reference marker


165 0.0960 0.1020s 0.1080s 0.1140s


-27 -54 -82 -109 -136 -164 -191 -218 -246 -273 -300 -328 -355 -382


Dipole Source on MRI


RD2 RLip


RD2 RLip


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