Diffusion tensor imaging of normal-appearing white matter as biomarker for radiation-induced late delayed cognitive decline.

Purpose: To determine whether early assessment of cerebral white matter degradation can predict late delayed cognitive decline after radiotherapy (RT).

Methods And Materials: Ten patients undergoing conformal fractionated brain RT participated in a prospective diffusion tensor magnetic resonance imaging study. Magnetic resonance imaging studies were acquired before RT, at 3 and 6 weeks during RT, and 10, 30, and 78 weeks after starting RT.

Multiparametric magnetic resonance imaging and repeated measurements of blood-brain barrier permeability to contrast agents.

Breakdown of the blood-brain barrier (BBB) is present in several neurological disorders such as stroke, brain tumors, and multiple sclerosis. Noninvasive evaluation of BBB breakdown is important for monitoring disease progression and evaluating therapeutic efficacy in such disorders. One of the few techniques available for noninvasively and repeatedly localizing and quantifying BBB damage is magnetic resonance imaging (MRI).

Dynamic contrast-enhanced magnetic resonance imaging as a biomarker for prediction of radiation-induced neurocognitive dysfunction.

Purpose: To determine whether early assessment of cerebral microvessel injury can predict late neurocognitive dysfunction after brain radiation therapy (RT).

Experimental Design: Ten patients who underwent partial brain RT participated in a prospective dynamic contrast-enhanced magnetic resonance imaging (MRI) study. Dynamic contrast-enhanced MRI was acquired prior to, at weeks 3 and 6 during, and 1 and 6 months after RT.

Radiation-induced changes in normal-appearing white matter in patients with cerebral tumors: a diffusion tensor imaging study.

Purpose: To quantify the radiation-induced changes in normal-appearing white matter before, during, and after radiotherapy (RT) in cerebral tumor patients.

Methods And Materials: Twenty-five patients with low-grade glioma, high-grade glioma, or benign tumor treated with RT were studied using diffusion tensor magnetic resonance imaging. The biologically corrected doses ranged from 50 to 81 Gy.

Step-down infusions of Gd-DTPA yield greater contrast-enhanced magnetic resonance images of BBB damage in acute stroke than bolus injections.

A rat model of transient suture occlusion of one middle cerebral artery (MCA) was used to create a unilateral reperfused cerebral ischemic infarct with blood-brain barrier (BBB) opening. Opening of the BBB was visualized and quantitated by magnetic resonance (MR) contrast enhancement with a Look-Locker T(1)-weighted sequence either following an intravenous bolus injection (n=7) or during a step-down infusion (n=7) of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA). Blood levels of Gd-DTPA after either input were monitored via changes in sagittal sinus relaxation rate.

Quantitative characterization of hemodynamic properties and vasculature dysfunction of high-grade gliomas.

Aberrations in tumor and peritumoral vasculature may not be distinguishable by cerebral blood flow (CBF) or cerebral blood volume (CBV) alone. The relationships between CBF and CBV were examined to estimate vasculature-specific hemodynamic characteristics. Twenty glioma patients were studied with dynamic susceptibility T2*-weighted MRI [(dynamic contrast-enhanced magnetic resonance imaging (DSC-MRI)] before and during week 1 and 3 of radiotherapy (RT).

The extent and severity of vascular leakage as evidence of tumor aggressiveness in high-grade gliomas.

Magnetic resonance imaging reveals heterogeneous regions within high-grade gliomas, such as a contrast-enhanced rim, a necrotic core, and non-contrast-enhanced abnormalities. It is unclear which of these regions best describes tumor aggressiveness. We hypothesized that the vascular leakage volume, reflecting disorganized angiogenesis typical of glioblastoma, would be a strong predictor of clinical outcome.

Survival prediction in high-grade gliomas by MRI perfusion before and during early stage of RT [corrected].

Purpose: To determine whether cerebral blood volume (CBV) and cerebral blood flow can predict the response of high-grade gliomas to radiotherapy (RT) by taking into account spatial heterogeneity and temporal changes in perfusion.

Methods And Materials: Twenty-three patients with high-grade gliomas underwent conformal RT, with magnetic resonance imaging perfusion before and at Weeks 1-2 and 3-4 during RT. Tumor perfusion was classified as high, medium, or low.

Acute blood-brain barrier opening in experimentally induced focal cerebral ischemia is preferentially identified by quantitative magnetization transfer imaging.

Pathologic changes in brain tissue during and after stroke may lead to injury of the blood-brain barrier (BBB) and subsequent hemorrhagic transformation (HT). In a rat model of HT, the apparent diffusion coefficient of water, cerebral blood flow, relaxation times, T(1) and T(2), and magnetization transfer (MT) related parameters (T(1sat), K(for) and the MT ratio) were repetitively measured during 3 h of focal ischemia and 2 h of reperfusion (n = 8). Areas of BBB opening were identified by sequential assay of the transcapillary influx of Gd-diethylenetriaminepentaacetic acid (Gd-DTPA) by MRI and (14)C-alpha-aminoisobutyric acid (AIB) by quantitative autoradiography.

Quantitation and localization of blood-to-brain influx by magnetic resonance imaging and quantitative autoradiography in a model of transient focal ischemia.

The ability of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) enhanced MRI to localize and quantitate blood-brain barrier (BBB) opening was evaluated against quantitative autoradiographic (QAR) imaging of (14)C-alpha-aminoisobutyric acid (AIB) distribution. The blood-to-brain transfer constant (K(i)) for Gd-DTPA was determined by MRI in rats after 3 h of focal cerebral ischemia plus 2.5 h of reperfusion (n = 9), and that of AIB was determined by QAR shortly thereafter.

Early prediction of gross hemorrhagic transformation by noncontrast agent MRI cluster analysis after embolic stroke in rat.

Background And Purpose: Our goal was to develop magnetic resonance indices, without image contrast agent enhancement, that predict hemorrhagic transformation (HT) in a rat model of embolic stroke.

Methods: Male Wistar rats subjected to embolic stroke with (n=12) or without (n=10) the combination treatment with recombinant tissue plasminogen activator and an anti-platelet glycoprotein IIb/IIIa antibody 7E3 F(ab')2 initiated at 4 hours after onset of stroke were investigated using a 7-T MRI system. Radiofrequency saturation T1 (T1sat) maps with magnetization transfer, apparent diffusion coefficient of water (ADCw) maps in 3 directions, and T2 maps were measured at 2, 24, and 48 hours after embolization.

Patlak plots of Gd-DTPA MRI data yield blood-brain transfer constants concordant with those of 14C-sucrose in areas of blood-brain opening.

The blood-to-brain transfer rate constant (K(i)) of Gd-DTPA was determined in MRI studies of a rat model of transient cerebral ischemia. The longitudinal relaxation rate, R(1), was estimated using repeated Look-Locker measurements. A model-independent analysis of deltaR(1), the Patlak plot, produced maps of K(i) for Gd-DTPA and the distribution volume of the mobile protons (V(p)) with intravascular-Gd changed R(1)'s.