Teilkörperhyperthermie mit einem Radiofrequenz-Multiantennen-Applikator unter online Kontrolle in einem 1,5 T MR-Tomographen

Abstract

Objective of this study is the integration of a multiantenna applicator for part-body hyperthermia (BSD 2000/3D) in a 1.5 T MR-tomograph (Siemens Magnetom Symphony) in order to perform noninvasive MR monitoring in real time to increase safety and effectiveness of heat treatments. The positioning unit is mechanically coupled to the MR gantry from the back side and the body coil is utilised for imaging. For that purpose, the hyperthermia antenna system (100 MHz, 1.500 W) and the MR receiver (63.9 MHs) have to be decoupled in terms of high frequency (filter) and electromagnetically (emc). The processing of MR data sets is performed in a hyperthermia planning system. A simultaneous operation of radiofrequency hyperthermia and MR system is possible at clinically relevant power levels. MR imaging is used for tumor-diagnostics (standard spin echo sequences), for hyperthermia planning (T1-weighted gradient echo sequences in equal- and opposed-phase techniques), and for temperature measurements according to the proton resonance frequency method (PRF method, phase evaluation registration using a gradient echo sequence with long echo time). In 33 patients with advanced pelvic and abdominal tumors we performed 150 heat sessions under MR monitoring. For 70% of these patients a visualisation of temperature sensitive data during treatment was possible. The evaluated difference images represent a superposition of real temperature -increase and a (temperature-induced) perfusion elevation. The -hybrid approach renders development of part body hyperthermia possible as an MR-controlled intervention in radiology.

Noninvasive Magnetic Resonance Thermography of Recurrent Rectal Carcinoma in a 1.5 Tesla Hybrid System

“…We installed a hybrid system (37) to perform regional hyperthermia in a multiantenna applicator under simultaneous MR monitoring and to acquire MR data sets during the entire treatment time of 90 minutes under routine conditions (37,38). Achieving an undisturbed MR data set during radiofrequency heating is a difficult task.…”

“…Our group developed a hybrid system where a SIGMA-Eye applicator (BSD Medical Corp.) was integrated into a mid-field system (1.5 Tesla, MR Symphony Quantum, Siemens) simultaneously working with amplifier power levels as high as 1,800 W (37). In phantoms and patients in the SIGMA-Eye applicator, we compared the different thermographic methods as outlined above (T1, diffusion, and PFS), and found advantages of the PFS method (26).…”

Noninvasive magnetic resonance thermography of soft tissue sarcomas during regional hyperthermia

“…Details of the integration of the SIGMA-Eye into the 1.5-Tesla MR system (Siemens Symphony, Erlangen, Germany) has been described elsewhere. 29,19 Basically, a filter system has been implemented to protect the MR system against the 100-MHz power signal and to eliminate any spectral contaminant of the heating system around the measuring frequency of 64-MHz proton resonance frequency.…”

Fast PRF-based MR thermometry using double-echo EPI: in vivo comparison in a clinical hyperthermia setting

“…The MR compatible HT unit was developed and incorporated into the MR system [20] inside the magnet bore. A deionized water bolus was attached to the HT unit's wall to efficiently couple the electromagnetic energy into the patient's body.…”