Systematic quality assurance of the BSD2000-3D MR-compatible hyperthermia applicator performance using MR temperature imaging

Abstract

The Pyrexar BSD2000-3D MR-compatible applicator provides robust and reproducible heating. The upper boundary of the 95% confidence interval of the spatial steering accuracy is 0.9 cm, i.e. sufficient to fulfil the criterion of ≤0.2 °C temperature variation due to positioning errors as defined by Canters et al.

Systematic review of pre-clinical and clinical devices for magnetic resonance-guided radiofrequency hyperthermia

“…The possibility to adapt/optimize SAR pattern in a phantom by employing MR thermometry in an iterative procedure were also shown for this applicator [47]. A recent more systematic quality assurance analysis of this system in a 1.5 T MRI scanner showed a mean maximum temperature increase (T increase, max ) in a Perfax homogeneous phantom of 5.9 ± 0.4 C, using 1000 W input power for 12.4 min, and a mean steering error of 0.4 ± 0.2 cm [44]. Clinical experiments in 15 patients [46] with pre-irradiated rectal recurrences showed significant correlation between the MRT-derived mean temperatures in the tumor with invasive measurements, tumor features (volume and location) and clinical response (p ¼ 0.04) [46].…”

“…After the early feasibility studies of diffusion-based MR thermometry methods, PRFS-based MRT methods were used in all studies. Spoiled gradient echo sequence with echo times close to the T2 Ã of muscle tissue is commonly used for PRFS-based MRT scans [44,49,60,62,64,68]. In addition to treatment monitoring, MRT also provides unique opportunities to validate EM models with 3D measurements.…”

“…This applicator consists of 12 dipole antenna pairs operating at 100 MHz, arranged on three rings of four dipole pairs each, that are independently controlled to steer the energy focus toward deep seated tumor volumes. This device has been validated both preclinically [40,[42][43][44] and clinically [45,46]. A systematic comparison of 3D-specific absorption rate (SAR) distribution between MRT and planning calculations in a homogenous cylindrical and heterogeneous elliptical phantom demonstrated a deviation in the range of 2-3 W/kg, i.e., below 10% [43].…”

A multi-institution study: comparison of the heating patterns of five different MR-guided deep hyperthermia systems using an anthropomorphic phantom

“…The existence of a thermal dose-effect relationship [12][13][14][15] strongly supports identical QA measurements among institutions to determine whether clinical results using these different systems can be meaningfully combined in multi-institution clinical studies [16]. We recently demonstrated that magnetic resonance thermometry (MRT) measurements, as facilitated by MR-radiofrequency (RF) hyperthermia systems, provide unprecedented 3D QA capabilities [17]. However, an anthropomorphic and human-shape representative phantom has not yet been utilized to compare results of multiple clinically active MR-compatible systems.…”

Model predictive control for MR-HIFU-mediated, uniform hyperthermia

“…Second, temperature monitoring is currently performed using thermocouples inside or near the heated tissue [19], which only provides sparse spatial sampling of the temperature. Radiofrequency-based hyperthermia devices integrated into a magnetic resonance imaging (MRI) scanner could address some of above shortcomings and are currently evaluated for use in clinical settings [20,21].…”