A Nonparametric Temperature Controller With Nonlinear Negative Reaction for Multi-Point Rapid MR-Guided HIFU Ablation

Abstract

Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is a noninvasive method for thermal ablation, which exploits the capabilities of magnetic resonance imaging (MRI) for excellent visualization of the target and for near real-time thermometry. Oncological quality of ablation may be obtained by volumetric sonication under automatic feedback control of the temperature. For this purpose, a new nonparametric (i.e., model independent) temperature controller, using nonlinear negative reaction, was designed and evaluated for the iterated sonication of a prescribed pattern of foci. The main objective was to achieve the same thermal history at each sonication point during volumetric MRgHIFU. Differently sized linear and circular trajectories were investigated ex vivo and in vivo using a phased-array HIFU transducer. A clinical 3T MRI scanner was used and the temperature elevation was measured in five slices simultaneously with a voxel size of 1 ×1 ×5 mm(3) and temporal resolution of 4 s. In vivo results indicated a similar thermal history of each sonicated focus along the prescribed pattern, that was 17.3 ± 0.5 °C as compared to 16 °C prescribed temperature elevation. The spatio-temporal control of the temperature also enabled meaningful comparison of various sonication patterns in terms of dosimetry and near-field safety. The thermal build-up tended to drift downwards in the HIFU transducer with a circular scan.

Simultaneous MR thermometry and acoustic radiation force imaging using interleaved acquisition

“…By tracking the delivered thermal dose, clinicians can ensure that the targeted volume has been adequately heated to induce cell death and that surrounding tissues are undamaged. In addition, MR thermometry has enabled the use of feedback controllers capable of automatically controlling the delivery of thermal dose during treatment . For improved monitoring, temporally constrained reconstruction (TCR) methods can reduce the update time between subsequent MR thermometry readings .…”

Mild hyperthermia by MR-guided focused ultrasound in an ex vivo model of osteolytic bone tumour: optimization of the spatio-temporal control of the delivered temperature

“…Extensive work has been reported for temperature control of ultrasound based thermal therapy [23, 24, 70, 71]. Some commercial products including Sonalleve ® and TUSLA ® devices from Profound Medical (2400 Skymark Avenue, Unit, Mississauga, ON L4 W 5K5, Canada), have standard capabilities for automatic feedback.…”

MRI-guided focused ultrasound surgery in musculoskeletal diseases: the hot topics

“…A model-based correction procedure for PRF shift thermometry errors caused by heat-induced magnetic susceptibility changes during HIFU ablation in tissues containing fat (breast fatty samples) was proposed by Baron et al 59 A non-parametric temperature controller with non-linear negative reaction for multipoint rapid MRgFUS was proposed by Petrusca et al 60 Experimental methods for improved spatial control of thermal lesions in MRgHIFU ablation were also proposed. 61 Available and accurate methods for retrospective reconstruction of the temperature maps useful in research settings were investigated.…”