Synchronized detection of minute electrical currents with MRI using Lorentz effect imaging

The blood oxygenation level-dependent (BOLD) effect is the most commonly used contrast mechanism in functional magnetic resonance imaging (fMRI), due to its relatively high spatial resolution and sensitivity. However, the ability of BOLD fMRI to accurately localize neuronal activation in space and time is limited by the inherent hemodynamic modulation. There is hence a need to develop alternative MRI methods that can directly image neuroelectric activity, thereby achieving both a high temporal resolution and spatial specificity as compared to conventional BOLD fMRI. In this paper, we extend the Lorentz effect imaging technique, which can detect spatially incoherent yet temporally synchronized minute electrical activity in a strong magnetic field, and demonstrate its feasibility for imaging randomly oriented electrical currents on the order of microamperes with a temporal resolution on the order of milliseconds in gel phantoms. This constitutes a promising step towards its application to direct imaging of neuroelectric activity in vivo, which has the same order of current density and temporal synchrony.     

Archimedes and the spirals: The heuristic background

In his work, The Method, Archimedes displays the heuristic technique by which he discovered many of his geometric theorems, but he offers there no examples of results from Spiral Lines. The present study argues that a number of theorems on spirals in Pappus' Collectio are based on early Archimedean treatments. It thus emerges that Archimedes' discoveries on the areas bound by spirals and on the properties of the tangents drawn to the spirals were based on ingenious constructions involving solid figures and curves. A comparison of Pappus' treatments with the Archimedean proofs reveals how a formal stricture against the use of solids in problems relating exclusively to plane figures induced radical modifications in the character of the early treatments.     

The treatment of vocal fold paralysis with injectable collagen: Clinical concerns

Over the past several years, the treatment of vocal cord paralysis has been substantially improved by the availability of injectable Teflon. This substance, suspended in glycerin, has provided consistent results in laryngeal rehabilitation due to its tissue tolerance and lack of resorption. Recently, moified bovine collagen has been proposed as an additional substance for use in vocal cord injections to treat vocal fold paralysis. Collagen is currently being used for augmentation of dermatologic scarring, especially on the face. It has undergone clinical trials and has now been approved for clinical use in this setting. Bovine collagen has proven very useful in scar modification. The injections are generally well tolerated and adverse responses do not often occur. Most of the adverse local reactions can be avoided by using a skin test on the forearm 1 month prior to treatment and excluding those patients with positive responses.     

The clinical voice laboratory: Clinical application of voice research

In the past decade the number of voice laboratories has increased dramatically. Their primary mission is to enhance patient care by the application of knowledge gained from basic research. They also are dedicated to further improvement of diagnostic and therapeutic resources. The strength of the voice laboratory lies in collaboration between the clinician and the scientist.