Non-Invasive in vivo Loss Tangent Imaging: Thermal Sensitivity Estimation at the Larmor Frequency
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Visualization of the tissue loss tangent property can provide distinct contrast andoffer new information related to tissue electrical properties. A method for noninvasiveimaging of the electrical loss tangent of tissue using magnetic resonanceimaging (MRI) was demonstrated, and the effect of loss tangent was observedthrough simulations assuming a hyperthermia procedure. For measurement oftissue loss tangent, radiofrequency field maps (B1+ complex map) were acquiredusing a double-angle actual flip angle imaging MRI sequence. The conductivityand permittivity were estimated from the complex valued B1+ map using Helmholtzequations. Phantom and ex-vivo experiments were then performed. Electromagneticsimulations of hyperthermia were carried out for observation of temperatureelevation with respect to loss tangent. Non-invasive imaging of tissue loss tangentvia complex valued B1+ mapping using MRI was successfully conducted. Simulationresults indicated that loss tangent is a dominant factor in temperature elevation inthe high frequency range during hyperthermia. Knowledge of the tissue loss tangentvalue can be a useful marker for thermotherapy applications.
Abstract
Visualization of the tissue loss tangent property can provide distinct contrast andoffer new information related to tissue electrical properties. A method for noninvasiveimaging of the electrical loss tangent of tissue using magnetic resonanceimaging (MRI) was demonstrated, and the effect of loss tangent was observedthrough simulations assuming a hyperthermia procedure. For measurement oftissue loss tangent, radiofrequency field maps (B1+ complex map) were acquiredusing a double-angle actual flip angle imaging MRI sequence. The conductivityand permittivity were estimated from the complex valued B1+ map using Helmholtzequations. Phantom and ex-vivo experiments were then performed. Electromagneticsimulations of hyperthermia were carried out for observation of temperatureelevation with respect to loss tangent. Non-invasive imaging of tissue loss tangentvia complex valued B1+ mapping using MRI was successfully conducted. Simulationresults indicated that loss tangent is a dominant factor in temperature elevation inthe high frequency range during hyperthermia. Knowledge of the tissue loss tangentvalue can be a useful marker for thermotherapy applications.
참고문헌 (30)
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