Respiration based steering for high intensity focused ultrasound liver ablation

Abstract

Purpose Respiratory motion makes hepatic ablation using high intensity focused ultrasound challenging. Previous HIFU liver treatment had required apnea induced during general anesthesia. We describe and test a system that allows treatment of the liver in the presence of breathing motion. Materials Mapping a signal from an external respiratory bellow to treatment locations within the liver allows the ultrasound transducer to be steered in real time to the target location. Using a moving phantom, three metrics were used to compare static, steered, and unsteered sonications: the area of sonications once a temperature rise of 15°C was achieved, the energy deposition required to reach that temperature, and the average rate of temperature rise during the first 10 seconds of sonication. Steered HIFU in vivo ablations of the porcine liver were also performed and compared to breath-hold ablations. Results For the last phantom metric, all groups were found to be statistically significantly different (p≤0.003). However, in the other two metrics, the static and unsteered sonications were not statistically different (p>0.9999). Steered in vivo HIFU ablations were not statistically significantly different from ablations during breath-holding. Conclusions A system for performing HIFU steering during ablation of the liver with breathing motion is presented and shown to achieve results equivalent to ablation performed with breath-holding.

Magnetic resonance thermometry: Methodology, pitfalls and practical solutions

“…In addition, these methods hold the promise to track motion like organ deformation using intrinsic vasculature as landmarks (84). Referenceless methods have been successfully applied in vivo (85,86).…”

Motion Correction Techniques for MR-Guided HIFU Ablation of Abdominal Organs

“…Most of these quantitative motion surrogate have been extracted from MR signal 34,[54][55][56][57] or US signal acquired with an external US probe. [58][59][60][61][62][63] Initial MR-based approaches used MR navigators 34, 54, 55 which do not require additional hardware and are easy to set up.…”

“…The steered ablation took 31.2 s to reach this point, whereas the breath-hold ablation took 26.7 s. The steered ablation required 16.7% more energy than the breath-hold case. Reproduced with permission of (Holbrook et al, 2014). 56 in successive MR images acquired continuously during the ablation process.…”

“…Reproduced with permission of (Holbrook et al, 2014). 56 in successive MR images acquired continuously during the ablation process. Several techniques have been developed to achieve efficient and robust MRthermometry/dosimetry in abdominal organs and are presented in the first part of this chapter.…”

Improving thermal dose accuracy in magnetic resonance-guided focused ultrasound surgery: Long-term thermometry using a prior baseline as a reference

“…As mentioned above, the periodic acquisition of a library of baselines not only through a treatment volume, but also throughout a complete respiratory cycle may account for respiratory motion, and has been shown in MRgFUS in the liver. 34 In addition, robust rotational and out-of-plane motion correction algorithms are still under investigation and can be computationally expensive. 35,36 Note that improved thermometry and shorter procedure times also have the potential to reduce patient motion.…”