Non-Invasive in vivo Loss Tangent Imaging: Thermal Sensitivity Estimation at the Larmor Frequency.
10.13104/imri.2016.20.1.36
- Author:
Narae CHOI
1
;
Min Oh KIM
;
Jaewook SHIN
;
Joonsung LEE
;
Dong Hyun KIM
Author Information
1. Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea. donghyunkim@yonsei.ac.kr
- Publication Type:Original Article
- Keywords:
Dielectric property imaging;
Loss tangent imaging;
MREPT;
Hyperthermia;
Thermal sensitivity
- MeSH:
Fever;
Hyperthermia, Induced;
Magnetic Resonance Imaging;
Magnets
- From:Investigative Magnetic Resonance Imaging
2016;20(1):36-43
- CountryRepublic of Korea
- Language:English
-
Abstract:
Visualization of the tissue loss tangent property can provide distinct contrast and offer new information related to tissue electrical properties. A method for non-invasive imaging of the electrical loss tangent of tissue using magnetic resonance imaging (MRI) was demonstrated, and the effect of loss tangent was observed through simulations assuming a hyperthermia procedure. For measurement of tissue loss tangent, radiofrequency field maps (B1+ complex map) were acquired using a double-angle actual flip angle imaging MRI sequence. The conductivity and permittivity were estimated from the complex valued B1+ map using Helmholtz equations. Phantom and ex-vivo experiments were then performed. Electromagnetic simulations of hyperthermia were carried out for observation of temperature elevation with respect to loss tangent. Non-invasive imaging of tissue loss tangent via complex valued B1+ mapping using MRI was successfully conducted. Simulation results indicated that loss tangent is a dominant factor in temperature elevation in the high frequency range during hyperthermia. Knowledge of the tissue loss tangent value can be a useful marker for thermotherapy applications.
