This years STM - Society of Thermal Medicine Annual Meeting will be held April 14-17, 2015 at the Buena Vista Palace Hotel in Orlando, FL. Pyrexar will be exhibiting in the main hall and our CTO, Paul Turner will be presenting an Abstract "Integration of Deep Hyperthermia with MR Imaging". Please drop by the booth and meet us.
Wednesday, April 15th, 2015 - 1:30pm - 3:15pm
Symposium: Thermal Modeling and Devices
Speaker: Paul Turner
INTEGRATION OF DEEP HYPERTHERMIA WITH MR IMAGING
Introduction- Designing a hyperthermia system that is integrated with MRI to obtain non-invasive thermometry during hyperthermia treatment involves many design constraints.
Method- The physical size and shape of the hyperthermia system must allow both the hyperthermia applicator and patient to fit inside the MR imagine opening. The equipment inserted into the MR aperture must not be magnetic materials. The equipment in the MR aperture must not create image artifacts that would distort the image quality. The hyperthermia equipment must not degrade MR receive signal to noise ratio. The receive MR coil can be integrated with of separate from the applicator. The MR should output the phase image as the proton frequency shift is temperature dependent. A suitable patient support system is needed to support the applicator and patient in the MR bore during treatments.
Suitable filtering must be incorporated in the output of the hyperthermia system to reduce RF noise and signals at the MR frequency. Filtering must be added to the MR receive path to prevent the RF output power of the hyperthermia applicator from saturating or damaging the MR sensitive receiver. The magnetic field of MR systems drifts with time and may not be uniform requiring a means to detect differences in the magnetic field to enable a compensation method such as silicone gel which has a signal level that does not change with temperature but does change with magnetic field. The hyperthermia system must not emit other spurious signals that may interfere with the MR imaging process. Results- The integration process has been successfully followed to integrate with 7 deep phased array systems. The first was at Munich with a 0.2T Siemens open Magnetom system.
Four others followed that were integrated with the Siemens 1.5T Symphony system. A research configuration was completed at Duke Univer sity with a 1.5T GE MR system (60dm diameter aperture). The most recent was in Rotterdam with a GE 450W 1.5T 450W MR system. This enables the initial phase images to be subtracted from images during treatment to produce a temperature difference image. It has been discovered that resonance of the cables and the hyperthermia dipoles can also cause shadowing of the imaging if there is a resonance of the cables at the MR operating frequency.
Conclusion- Following these steps, successful integration of hyperthermia systems with MR for non-invasive thermometry during hyperthermia have been achieved.