DTI Abnormalities Related to Glioblastoma: A Prospective Comparative Study with Metastasis and Healthy Subjects

Abstract

(1) Background: Glioblastoma multiforme (GBM) shows complex mechanisms of spreading of the tumor cells, up to remote areas, and little is still known of these mechanisms, thus we focused on MRI abnormalities observable in the tumor and the brain adjacent to the lesion, up to the contralateral hemisphere, with a special interest on tensor diffusion imaging informing on white matter architecture; (2) Material and Methods: volumes, macroscopic volume (MV), brain-adjacent-tumor (BAT) volume and abnormal color-coded DTI volume (aCCV), and region-of-interest samples (probe volumes, ipsi, and contra lateral to the lesion), with their MRI characteristics, apparent diffusion coefficient (ADC), fractional anisotropy (FA) values, and number of fibers (DTI fiber tracking) were analyzed in patients suffering GBM (n = 15) and metastasis (n = 9), and healthy subjects (n = 15), using ad hoc statistical methods (type I error = 5%) (3) Results: GBM volumes were larger than metastasis volumes, aCCV being larger in GBM and BAT ADC was higher in metastasis, ADC decreased centripetally in metastasis, FA increased centripetally either in GBM or metastasis, MV and BAT FA values were higher in GBM, ipsi FA values of GBM ROIs were higher than those of metastasis, and the GBM ipsi number of fibers was higher than the GBM contra number of fibers; (4) Conclusions: The MV, BAT and especially the aCCV, as well as their related water diffusion characteristics, could be useful biomarkers in oncology and functional oncology.

Keywords: DTI; MRI; anisotropy; biomarker; brain adjacent to tumor; diffusion; glioblastoma; infiltration; metastasis; tractography.

Figure 1

MRI objects schematized on a simplified axial MRI slice (ventricles in gray): (1) volumes, the macroscopic volume (MV), the brain adjacent to tumor (BAT) and the abnormal color-coded volume (aCCV); (2) ROIs in the corona radiata (CR-contra) and white matter fascicles (WMf), ispi- and contra- lateral to the lesion.

Figure 2

Manual contouring of the macroscopic volume (MV, orange), the BAT volume (blue) and the abnormal color-coded volume (aCCV, yellow) on axial MRI of GBM ((A); patient 11; left GBM) and metastasis ((B); patient 3; right metastasis) cases; left column, 3D T1-enhanced sequence; intermediate column, B0 diffusion weighted sequence; right column, color-coded DTI map.

Figure 3

3D rendering (superior view) of the macroscopic volume (MV, orange), the BAT volume (light blue) and the abnormal color-coded volume (aCCV, light yellow) within the brain volume (same patients of the Figure 2; (A), GBM; (B), metastasis); fascicles computed (fiber tracking DTI) from WMf-ipsi and WMf-contra are embedded.

Figure 4

Artistic drawing of MRI characteristics of GBM (A), and metastasis (B): the highest ADC value is in MV; the BAT ADC value is higher in metastasis; a high FA value is in GBM aCCV; fascicles are depicted as white/black ribbons, structurally lesioned in red, and functionally harmed in orange.