Radiofrequency applicator concepts for simultaneous MR imaging and hyperthermia treatment of glioblastoma multiforme

Abstract

Glioblastoma multiforme is the most frequent and most aggressive malignant brain tumor with de facto no long term curation by the use of current multimodal therapeutic approaches. The efficacy of brachytherapy and enhancing interstitial hyperthermia has been demonstrated. RF heating at ultrahigh fields (B 0 =7.0T, f=298MHz) has the potential of delivering sufficiently large thermal dosage for hyperthermia of relatively large tumor areas. This work focuses on electromagnetic field (EMF) simulations and provides realistic applicator designs tailored for simultaneous RF heating and MRI. Our simulations took advantage of target volumes derived from patient data, and our preliminary results suggest that RF power can be focused to both a small tumor area and a large clinical target volume.

Controlled Release of Therapeutics from Thermoresponsive Nanogels: A Thermal Magnetic Resonance Feasibility Study

“…This approach constrained the heating rate to ΔT = 0.3 °C/min for a peak power of P = 100 W and a duty cycle of 10%. To enhance the heating rate, an array of RF antennas can be exploited [ 30 , 31 ]. This approach would afford the shaping and the steering of the temperature hotspot and would support parallel MR imaging to reduce acquisition times needed for temperature monitoring of larger volumes [ 41 , 42 ].…”

“…Pretreatment temperature simulations should be adopted for each patient and tumor to ensure maximum efficacy as the tumor type, morphology, volume, and perfusion could impact the heating as well as the uptake of the nanocarriers. For smaller tumors it is easier to achieve uniform heating across the target [ 31 ] and the accumulation of drug nanocarriers is higher [ 48 ]. Although hyperthermia can increase the EPR effect, in reality it is a heterogeneous phenomenon so that certain areas of the tumor can still not be reachable [ 11 , 23 ].…”

“…For example, for brain tissue, a hotspot size as small as (6 × 9) mm 2 was reported for an RF frequency of f = 297 MHz [ 29 , 30 ]. On the other hand, large heating volumes (~500 mL) can also be achieved by manipulating the phase, power, and frequency of different channels of the array [ 31 , 32 ]. To apply heat into a target site, controlled manipulation of temperature is required while concomitantly characterizing its outcome in vivo.…”

Wideband Self‐Grounded Bow‐Tie Antenna for Thermal MR

“…Ensuring a patient‐ and problem‐oriented adaptation of the size, uniformity and location of the RF energy deposition in the target region is highly relevant for the thermal intervention, with the focal point quality being governed by the radiation pattern of the single RF transmit element, the RF channel count and the thermal intervention radiofrequency of the RF applicator . Reports on the radiation pattern of resonant structures underline the benefits of dipole antenna arrays for enhancing the focal point quality in thermal interventions .…”

“…A compact wideband antenna setup based on a self‐grounded bow‐tie (SGBT) antenna is a potential answer to the need for multiple rings and a high channel count setup to enable broadband thermal intervention . While several previous reports on RF antenna systems have addressed these multiple issues individually, our objective with this new design was to achieve a comprehensive solution.…”