State-of-the-art imaging for glioma surgery

Abstract

Diffuse gliomas are infiltrative primary brain tumors with a poor prognosis despite multimodal treatment. Maximum safe resection is recommended whenever feasible. The extent of resection (EOR) is positively correlated with survival. Identification of glioma tissue during surgery is difficult due to its diffuse nature. Therefore, glioma resection is imaging-guided, making the choice for imaging technique an important aspect of glioma surgery. The current standard for resection guidance in non-enhancing gliomas is T2 weighted or T2w-fluid attenuation inversion recovery magnetic resonance imaging (MRI), and in enhancing gliomas T1-weighted MRI with a gadolinium-based contrast agent. Other MRI sequences, like magnetic resonance spectroscopy, imaging modalities, such as positron emission tomography, as well as intraoperative imaging techniques, including the use of fluorescence, are also available for the guidance of glioma resection. The neurosurgeon's goal is to find the balance between maximizing the EOR and preserving brain functions since surgery-induced neurological deficits result in lower quality of life and shortened survival. This requires localization of important brain functions and white matter tracts to aid the pre-operative planning and surgical decision-making. Visualization of brain functions and white matter tracts is possible with functional MRI, diffusion tensor imaging, magnetoencephalography, and navigated transcranial magnetic stimulation. In this review, we discuss the current available imaging techniques for the guidance of glioma resection and the localization of brain functions and white matter tracts.

Keywords: Brain functionality; Extent of resection; Glioma; Imaging; Neurosurgery.

Fig. 1

Exemplary standard and advanced imaging. A Patient with a right parietal enhancing glioblastoma, IDH-wild type. Upper left: T1-weighted MRI with a gadolinium-based contrast agent, Upper right: FLAIR MRI, lower left: multivoxel MRSI CNI projected on the FLAIR MRI. Lower right: amino acid ([¹⁸F]FET) PET. B Patient with a left temporal non-enhancing diffuse astrocytoma, IDH-mutant. The crosshair is projected to indicate the region with MRSI CNI and PET abnormalities just outside the FLAIR MRI abnormalities. Upper left: T2-weighted MRI, Upper right: FLAIR MRI, Lower left: multivoxel MRSI CNI projected on the FLAIR MRI, Lower right: amino acid ([¹⁸F]FET) PET

Fig. 2

Examples of intraoperative imaging. A Intraoperative MRI of an enhancing right frontal glioblastoma with clockwise images of the progression of the resection with clear brain shift. Image courtesy of Dr. P Kubben [46]. B Intraoperative ultrasound of a left parietal glioblastoma

Fig. 3

Example of intraoperative fluorescence. Intraoperative image of 5-ALA-guided resection of superficial glioblastoma with clear pink fluorescence of the tumor with the surrounding normal tissue appearing blue

Fig. 4

Examples of imaging for localization of brain functions and white matter tracts. A Functional MRI of a patient with a language located in the right hemisphere, which was confirmed with a WADA test. B Visualization of the left corticospinal tract (green), fasciculate arcuatus (orange) and inferior fronto-occipital fasciculus (yellow) using DTI in a patient with a left temporal diffuse astrocytoma, IDH-mutant. C Localization of the left motor cortex using MEG in a patient with a diffuse astrocytoma, IDH-mutant