Multifocal arterial wall contrast - enhancement in ischemic stroke: A mirror of systemic inflammatory response in acute stroke.

PURPOSE: Intracranial plaque gadolinium enhancement revealed by high-resolution MRI imaging (HR MRI) is considered as a marker of plaque inflammation, a contributing factor of plaque unstability. The aim of the present study was to assess the distribution of gadolinium enhancement in intracranial atherosclerosis. METHODS: Single center analysis of ischemic stroke patients with intracranial atherosclerotic stenosis of M1 or M2 segments of middle cerebral artery, or terminal internal carotid artery (ICA) based on CT-angio or MR-angio. High-resolution MRI imaging (HRMRI) was performed within 6 first weeks following the index event, with 3DT2 BB (black-blood) and 3D T1 BB MR sequences pre and post-contrast administration. RESULTS: We identified 8 patients with 14 plaques, 4 were deemed non-culprit and 10 culprit. All culprit plaques (10/10 plaques) and 3 out of 4 non-culprit plaques showed a gadolinium enhancement. CONCLUSION: At the acute/subacute stage of stroke, a gadolinium enhancement may affect multiple asymptomatic intracranial plaques and may reflect a global inflammatory state.

Reconstruction of vascular blood flow in a vessel from tomographic projections.

In this work, we study the measurement of blood velocity with contrast enhanced computed tomography. The reconstruction is based on CT projections perpendicular to the main axis of the vessel and on a partial differential equation describing the propagation of the contrast agent. The inverse problem is formulated as an optimal control problem with the transport equation as constraint. The velocity field is obtained with stationary and unstationary Navier-Stokes equations and it is reconstructed with the adjoint method. The velocity and the density of the contrast agent are well reconstructed. The reconstruction results obtained are better for the axial component of the velocity than for transverse components.

MR imaging assessment of myocardial edema with T2 mapping.

Cardiac magnetic resonance (CMR) provides a high signal-to-noise ratio, high spatial and temporal resolutions, as well as a delayed-enhancement sequence and is therefore considered a reference technique in the field of cardiac imaging. However, currently available sequences are not adequate to assess some pathologic conditions, such as myocardial edema. T2 mapping sequences generate parametric images that are based on the transverse relaxation time (T2) for each voxel. In case of edema, the T2 relaxation time is longer. This review summarizes current knowledge on CMR T2 mapping for assessing myocardial edema.

Photon counting spectral CT component analysis of coronary artery atherosclerotic plaque samples.

OBJECTIVE: To evaluate the capabilities of photon counting spectral CT to differentiate components of coronary atherosclerotic plaque based on differences in spectral attenuation and iodine-based contrast agent concentration. METHODS: 10 calcified and 13 lipid-rich non-calcified histologically demonstrated atheromatous plaques from post-mortem human coronary arteries were scanned with a photon counting spectral CT scanner. Individual photons were counted and classified in one of six energy bins from 25 to 70 keV. Based on a maximum likelihood approach, maps of photoelectric absorption (PA), Compton scattering (CS) and iodine concentration (IC) were reconstructed. Intensity measurements were performed on each map in the vessel wall, the surrounding perivascular fat and the lipid-rich and the calcified plaques. PA and CS values are expressed relative to pure water values. A comparison between these different elements was performed using Kruskal-Wallis tests with pairwise post hoc Mann-Whitney U-tests and Sidak p-value adjustments. RESULTS: RESULTS for vessel wall, surrounding perivascular fat and lipid-rich and calcified plaques were, respectively, 1.19 ± 0.09, 0.73 ± 0.05, 1.08 ± 0.14 and 17.79 ± 6.70 for PA; 0.96 ± 0.02, 0.83 ± 0.02, 0.91 ± 0.03 and 2.53 ± 0.63 for CS; and 83.3 ± 10.1, 37.6 ± 8.1, 55.2 ± 14.0 and 4.9 ± 20.0 mmol l(-1) for IC, with a significant difference between all tissues for PA, CS and IC (p < 0.012). CONCLUSION: This study demonstrates the capability of energy-sensitive photon counting spectral CT to differentiate between calcifications and iodine-infused regions of human coronary artery atherosclerotic plaque samples by analysing differences in spectral attenuation and iodine-based contrast agent concentration. ADVANCES IN KNOWLEDGE: Photon counting spectral CT is a promising technique to identify plaque components by analysing differences in iodine-based contrast agent concentration, photoelectric attenuation and Compton scattering.