Biomedical subjects

A G Webb

Publications and source records attributed to A G Webb.

39 records · Page 3Linked to original sources

PubMedDate not supplied

Applications of reduced-encoding MR imaging with generalized-series reconstruction (RIGR).

The RIGR (reduced-encoding imaging by generalized-series reconstruction) technique for magnetic resonance imaging uses a high-resolution reference image as the basis set for the reconstruction of subsequent images acquired with a reduced number of phase-encoding steps. The technique allows increased temporal resolution in applications requiring repeated acquisitions, such as the dynamic imaging of contrast agent biodistribution, and in intrinsically time-consuming protocols such as the acquisition of a series of T2-weighted images. Several examples are presented to demonstrate that a four- to eightfold improvement in spatial or temporal resolution can be achieved with this technique.

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PubMedDate not supplied

Sonochemically produced fluorocarbon microspheres: a new class of magnetic resonance imaging agent.

With the intent of increasing the signal-to-noise ratio (SNR) of fluorine magnetic resonance imaging and enabling new applications, we have developed a novel class of agents based on protein encapsulation of fluorocarbons. Microspheres formed by high-intensity ultrasound have a gaussian size distribution with an average diameter of 2.5 microns. As with conventional emulsions, these microspheres target the reticuloendothelial system. However, our sonochemically produced microspheres, because of a high encapsulation efficiency, show increases in the SNR of up to 300% compared to commercially available emulsions. We also demonstrate an increase in the circulation lifetime of the microspheres with the bloodstream by more than 30-fold with a chemical modification of the outer surface of the microsphere. Finally, by encapsulating mixtures of fluorocarbons that undergo solid/liquid phase transitions, we can map temperature in the reticuloendothelial system, with signal changes of approximately 20-fold over a 5 degrees C range.

Animals↗

PubMedDate not supplied

In-vivo NMR thermometry with liposomes containing 59Co complexes.

The ability to make localized temperature measurements in tissue during hyperthermia treatment of cancer is an essential factor in optimizing its efficacy. To this end we have developed and evaluated the complex tris(ethylenediamine) cobalt(III) trichloride as a temperature sensor by determining the temperature dependence of it 59Co nuclear magnetic resonance chemical shift. Encapsulating this complex within liposomes targets the agent to the reticuloendothelial system. Temperature changes of the order of 0.1 degrees C have been measured in vivo on rats, and the half-life of the complex within the body determined by plasma emission spectroscopy.

Animals↗