Cerebral microbleeds in adult survivors of childhood acute lymphoblastic leukemia treated with cranial radiation.

Cranial radiation therapy is associated with white matter-specific brain injury, cortical volume loss, mineralization, microangiopathy and neurocognitive impairment in survivors of childhood acute lymphoblastic leukemia. In this retrospective cross-sectional analysis, neurocognitive testing and 3 T brain MRI's were obtained in 101 survivors treated with cranial radiation. Small focal intracerebral hemorrhages only visible on exquisitely sensitive MRI sequences were identified and localized using susceptibility weighted imaging.

Paired self-compensated spin-lock preparation for improved T1ρ quantification.

Purpose: Spin-lock (SL) imaging allows quantification of the spin-lattice relaxation time in the rotating frame (T1ρ). B0 and B1 inhomogeneities impact T1ρ quantification because the preparatory block in SL imaging is sensitive to the field heterogeneities. Here, a modified preparatory block (PSC-SL) is proposed that attempts to alleviate SL sensitivity to field inhomogeneities in scenarios where existing approaches fail, i.

Extracting surface activation time from the optically recorded action potential in three-dimensional myocardium.

Optical mapping has become an indispensible tool for studying cardiac electrical activity. However, due to the three-dimensional nature of the optical signal, the optical upstroke is significantly longer than the electrical upstroke. This raises the issue of how to accurately determine the activation time on the epicardial surface.

Imaging electrical excitation inside the myocardial wall.

Cardiac arrhythmias are often triggered by ectopic membrane depolarization originating deep inside the myocardial wall. Here we propose a new method utilizing a novel near-infrared voltage-sensitive fluorescent dye DI-4-ANBDQBS to determine the three-dimensional (3D) coordinates of the sources of such depolarization. We tested the method in live preparations of pig left and right ventricular myocardium (thickness 8-18 mm) and phantoms imitating the optical properties of myocardial tissue.

Probing field-induced tissue polarization using transillumination fluorescent imaging.

Despite major successes of biophysical theories in predicting the effects of electrical shocks within the heart, recent optical mapping studies have revealed two major discrepancies between theory and experiment: 1), the presence of negative bulk polarization recorded during strong shocks; and 2), the unexpectedly small surface polarization under shock electrodes. There is little consensus as to whether these differences result from deficiencies of experimental techniques, artifacts of tissue damage, or deficiencies of existing theories. Here, we take advantage of recently developed near-infrared voltage-sensitive dyes and transillumination optical imaging to perform, for the first time that we know of, noninvasive probing of field effects deep inside the intact ventricular wall.

Spontaneous onset of atrial fibrillation.

Most commonly, atrial fibrillation is triggered by rapid bursts of electrical impulses originating in the myocardial sleeves of pulmonary veins (PVs). However, the nature of such bursts remains poorly understood. Here, we propose a mechanism of bursting consistent with the extensive empirical information about the electrophysiology of the PVs.

A novel near-infrared voltage-sensitive dye reveals the action potential wavefront orientation at increased depths of cardiac tissue.

Recently, novel near-infrared (NIR) voltage-sensitive dyes were developed for imaging electrical activity in blood-perfused hearts and for tomographic applications. However, their usefulness for conventional surface mapping is unclear. The spectral shift to the NIR range significantly increases the penetration depth of light into the tissue, thus increasing the intramural volume contributing to the optical action potential (OAP).

Monitoring intramyocardial reentry using alternating transillumination.

Intramyocardial reentry is implicated as a primary cause of the most deadly cardiac arrhythmias known as polymorphic ventricular tachycardia and ventricular fibrillation. However, the mechanisms involved in the triggering of such reentry and controlling its subsequent dynamics remain poorly understood. One of the major obstacles has been a lack of adequate tools that would enable 3D imaging of electrical excitation and reentry inside thick ventricular wall.

Near-infrared voltage-sensitive fluorescent dyes optimized for optical mapping in blood-perfused myocardium.

Background: Styryl voltage-sensitive dyes (e.g., di-4-ANEPPS) have been used successfully for optical mapping in cardiac cells and tissues.

New near-infrared optical probes of cardiac electrical activity.

Styryl voltage-sensitive dyes (e.g., di-4-ANEPPS) have been widely and successfully used as probes for mapping membrane potential changes in cardiac cells and tissues.