Measuring local RF heating in MRI: Simulating perfusion in a perfusionless phantom

Purpose: To overcome conflicting methods of local RF heating measurements by proposing a simple technique for predicting in vivo temperature rise by using a gel phantom experiment. Materials and Methods: In vivo temperature measurements are difficult to conduct reproducibly; fluid phantoms introduce convection, and gel phantom lacks perfusion. In the proposed method the local temperature rise is measured in a gel phantom at a timepoint that the phantom temperature would be equal to the perfused body steady-state temperature value. The idea comes from the fact that the steady-state temperature rise in a perfused body is smaller than the steady-state temperature increase in a perfusionless phantom. Therefore, when measuring the temperature on a phantom there will be the timepoint that corresponds to the perfusion time constant of the body part. Results: The proposed method was tested with several phantom and in vivo experiments. Instead, an overall average of 30.8% error can be given as the amount of underestimation with the proposed method. This error is within the variability of in vivo experiments (45%). Conclusion: With the aid of this reliable temperature rise prediction the amount of power delivered by the scanner can be controlled, enabling safe MRI examinations of patients with implants. © 2007 Wiley-Liss, Inc

Modulation of multilayer InAs quantum dot waveguides under applied electric field

Electric field dependence of optical modulation in self assembled InAs quantum dot waveguides have been studied at 1300 and 1500 nm. Electro-absorption and electro-optic coefficients of these waveguides have been obtained at both wavelengths. © 2007 Optical Society of America

Electro-optic modulation of InAs quantum dot waveguides

The linear electro-optic properties in waveguides containing self-organized In As quantum dots were studied experimentally. Fabry-Perot measurements at 1515 nm on InAs/GaAs quantum dot structures yield a significantly enhanced linear electro-optic efficiency compared to bulk GaAs

Characterization of multilayer self-organized InAs quantum dot embedded waveguides at 1.3 and 1.5 μm

In this paper, we characterized the electro-optic coefficient and loss of multilayer InAs quantum dot laser structures at 1309 and 1515 nm. Quantum dot waveguides were grown by molecular beam epitaxy, where the active region is formed by three or five layers of self-assembled InAs QDs. Loss characterization were carried out by using a 1.3 µm light from a thermally tunable laser. Transmission through the device was recorded as a function of wavelength. Loss coefficient is found to be wavelength and bias voltage dependent

Electric field dependence of modulation in multilayer inas quantum dot waveguides

[No abstract available