Gibbs point field model quantifies disorder in microvasculature of U87-glioblastoma

Whole-Brain Vascular Architecture Mapping Identifies Region-Specific Microvascular Profiles in Vivo

BACKGROUND AND PURPOSE

The novel MR imaging technique of vascular architecture mapping allows in vivo characterization of local changes in cerebral microvasculature, but reference ranges for vascular architecture mapping parameters in healthy brain tissue are lacking, limiting its potential applicability as an MR imaging biomarker in clinical practice. We conducted whole-brain vascular architecture mapping in a large cohort to establish vascular architecture mapping parameter references ranges and identify region-specific cortical and subcortical microvascular profiles.

MATERIALS AND METHODS

This was a single-center examination of adult patients with unifocal, stable low-grade gliomas with multiband spin- and gradient-echo EPI sequence at 3T using parallel imaging. Voxelwise plotting of resulting values for gradient-echo (R2*) versus spin-echo (R2) relaxation rates during contrast agent bolus administration generates vessel vortex curves that allow the extraction of vascular architecture mapping parameters representative of, eg, vessel type, vessel radius, or CBV in the underlying voxel. Averaged whole-brain parametric maps were calculated for 9 parameters, and VOI analysis was conducted on the basis of a standardized brain atlas and individual cortical GM and WM segmentation.

RESULTS

Prevalence of vascular risk factors among subjects (n = 106; mean age, 39.2 [SD, 12.5] years; 56 women) was similar to those in the German population. Compared with WM, we found cortical GM to have larger mean vascular calibers (5.80 [SD, 0.59] versus 4.25 [SD, 0.62] P < .001), increased blood volume fraction (20.40 [SD, 4.49] s-1 versus 11.05 [SD, 2.44] s-1; P < .001), and a dominance of venous vessels. Distinct microvascular profiles emerged for cortical GM, where vascular architecture mapping vessel type indicator differed, eg, between the thalamus and cortical GM (mean, -2.47 [SD, 4.02] s-2 versus -5.41 [SD, 2.84] s-2; P < .001). Intraclass correlation coefficient values indicated overall high test-retest reliability for vascular architecture mapping parameter mean values when comparing multiple scans per subject.

CONCLUSIONS

Whole-brain vascular architecture mapping in the adult brain reveals region-specific microvascular profiles. The obtained parameter reference ranges for distinct anatomic and functional brain areas may be used for future vascular architecture mapping studies on cerebrovascular pathologies and might facilitate early discovery of microvascular changes, in, eg, neurodegeneration and neuro-oncology.

Advanced Computational Methods to Evaluate Vascular Heterogeneity in Tumor Tissue Based on Single Plane Illumination Microscopy

During tumor growth, the complex composition of vasculature is prone to dynamic changes due to mechanic and biochemical challenges. Perivascular invasion of tumor cells to co-opt existing vasculature, but also formation of de-novo vasculature and other effects on the vascular network, may lead to altered geometric vessel properties as well as changes in vascular network topology, which is defined by vascular multifurcations and connections between vessel segments. The intricate organization and heterogeneity of the vascular network can be analyzed with advanced computational methods to uncover vascular network signatures that may allow differentiating between pathological and physiological vessel regions. Herein, we present a protocol to evaluate vascular heterogeneity in whole vascular networks, using morphological and topological measures. The protocol was developed for single plane illumination microscopy images of mice brain vasculature but can be applied to any vascular network.