Magnetic resonance imaging of magnetic fields from radiofrequency ablation at 64 megahertz
Abstract/Contents
- Abstract
- Radiofrequency ablation (RFA) is an effective minimally invasive treatment for tumors, using RF currents to deposit energy and create local heating. MRI has been proposed to monitor RFA due to its ability to acquire images of heating. If the ablation is performed at 64 MHz (the Larmor frequency of a 1.5 Tesla MRI system) instead of the typical 460-500 kHz, the magnetic fields associated with the RF currents can be used as the MR excitation. RF field mapping techniques can then be used to image those magnetic fields, providing information about the underlying current density. The current distribution will change during the course of ablation due to changes in the complex conductivity of the treated tissue. Knowledge of the magnetic fields could be used to steer currents into a more efficient ablation pattern as well as evaluate the process of the ablation by monitoring changes in the electrical properties of the tissue. In this thesis, I show results from performing RFA at 64 MHz and discuss improvements to MRI RF field mapping techniques for imaging the fields from the ablation currents. I have optimized the Actual Flip-Angle (AFI) RF field mapping sequence to achieve the best SNR of the field maps within a given scan time by considering noise propagation, errors from T1 relaxation and incomplete spoiling of transverse magnetization. I have then designed an adiabatic partial passage pulse that, when used in the AFI sequence, captures a much larger dynamic range, up to 16:1. Finally, I have performed RFA at 64 MHz and imaged the RF magnetic fields.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Shultz, Kimberly Merritt |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering |
| Primary advisor | Pauly, John (John M.) |
| Thesis advisor | Pauly, John (John M.) |
| Thesis advisor | Nishimura, Dwight George |
| Thesis advisor | Scott, Greig Cameron, 1962- |
| Advisor | Nishimura, Dwight George |
| Advisor | Scott, Greig Cameron, 1962- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Kimberly Merritt Shultz. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Ph. D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Kimberly Merritt Shultz
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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