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Reduction of electronic noise from radiofrequency generator during radiofrequency ablation in interventional MRI
Thomas Oshiro1, Usha Sinha, David Lu
1Department of Radiological Sciences, UCLA School of Medicine, Los Angeles, CA, USA.
Abstract:
MRI has been used increasingly in the recent past for the guidance and monitoring of minimally invasive interventional procedures, using typically radiofrequency (RF) and laser energy, cryoablation, and percutaneous ethanol. RF energy has been used over the last 30 years for the ablation of tissues. Its use in conjunction with MRI for monitoring is limited, however, because of the electronic noise produced by the RF generators, which can significantly deteriorate image quality. The objective of this work was to devise methods by which this noise can be reduced to an acceptable level to allow simultaneous acquisition of MR images for monitoring purposes with the application of RF energy. Three different methods of noise reduction were investigated in a 0.2 T MR scanner: filtration using external hardware circuitry, MR scanner software-controlled filtration, and keyholing. The last two methods were unable by themselves to suppress the noise to an acceptable degree. Hardware filtration, however, provides excellent suppression of RF noise and is able to withstand up to 12 W of RF energy. When all the three approaches are combined, significant reduction of RF noise is achieved. The feasibility of creating an RF lesion of about 1.2 cm diameter in vivo in a porcine model simultaneously with temperature-sensitive MRI with adequate noise suppression is demonstrated.
Insights
This study developed methods to reduce radiofrequency (RF) generator noise during MRI-guided procedures. Combining hardware filtration with software techniques enables simultaneous RF ablation monitoring and imaging.
Area of Science:
- Medical Imaging
- Interventional Radiology
- Biomedical Engineering
Background:
- Magnetic Resonance Imaging (MRI) is increasingly used for minimally invasive procedures.
- Radiofrequency (RF) energy is common in tissue ablation but generates noise that degrades MRI quality.
- Simultaneous MRI monitoring during RF ablation is challenging due to electronic noise interference.
Purpose of the Study:
- To develop and evaluate methods for reducing RF generator noise during MRI.
- To enable simultaneous MRI image acquisition and RF energy application for procedure monitoring.
- To assess the feasibility of creating RF lesions while maintaining MRI quality.
Main Methods:
- Investigated three noise reduction techniques: external hardware filtration, MR scanner software filtration, and keyholing.
- Evaluated methods on a 0.2 T MR scanner.
- Tested feasibility in vivo using a porcine model with temperature-sensitive MRI.
Main Results:
- Software filtration and keyholing alone were insufficient for noise suppression.
- External hardware filtration effectively suppressed RF noise and handled up to 12 W of RF energy.
- Combining all three methods significantly reduced RF noise.
- Demonstrated successful creation of a 1.2 cm RF lesion in vivo with simultaneous MRI monitoring.
Conclusions:
- A combined approach of hardware filtration, software filtration, and keyholing effectively reduces RF noise during MRI.
- This method allows for simultaneous MRI monitoring of RF ablation procedures.
- The technique is feasible for creating RF lesions in vivo with adequate noise suppression.