A planning strategy for combined motion-assisted/gated MR guided focused ultrasound treatment of the pancreas

Abstract

Objective: To develop and evaluate a combined motion-assisted/gated MRHIFU heating strategy designed to accelerate the treatment procedure by reducing the required number of sonications to ablate a target volume in the pancreas. Methods: A planning method for combined motion-assisted/gated MRHIFU using 4D-MRI and motion characterization is introduced. Six healthy volunteers underwent 4D-MRI for target motion characterization on a 3.0-T clinical scanner. Using displacement patterns, simulations were performed for all volunteers for three sonication approaches: gated, combined motion-assisted/gated, and static. The number of sonications needed to ablate the pancreas head was compared. The influence of displacement amplitude and target volume size was investigated. Spherical target volumes (8, 15, 20 and 34 mL) and displacement amplitudes ranging from 5 to 25 mm were evaluated. For this case, the number of sonications required to ablate the whole target was determined. Results: The number of required sonications was lowest for a static target, 62 on average (range 49-78). The gated approach required most sonications, 126 (range 97-159). The combined approach was almost as efficient as the hypothetical static case, with an average of 78 (range 53-123). Simulations showed that with a 5-mm displacement amplitude, the target could be treated by making use of motion-assisted MRHIFU sonications only. In that case, this approach allowed the lowest number of sonication, while for 10 mm and above, the number of required sonications increased. Conclusion: The use of a combined motion-assisted/gated MRHIFU strategy may accelerate tumor ablation in the pancreas when respiratory-induced displacement amplitudes are between 5 and 10 mm. ARTICLE HISTORYThermal ablation; high intensity focused ultrasound; imaging (i.e.; MRI); modeling (i.e.; treatment planning)

Latest Advances in the Use of Therapeutic Focused Ultrasound in the Treatment of Pancreatic Cancer

“…To improve the safety and efficacy of HIFU treatments, methods of compensating for respiratory motion and improving thermometry have been developed, e.g., by fluidfilling the digestive tract surrounding the pancreas of patients [166][167][168][169][170]. For example, simulation data in seven patients showed that the air in the digestive tract and its proximity to the pancreas led to errors in temperature of more than 10 • C due to differences in the magnetic susceptibility between the two tissues and peristaltic motion.…”

Technical note: Low‐cost MR‐compatible pneumatic respiratory organ motion simulator for the development of MR‐guided thermal therapy

“…Abdominal organ motion causes significant errors in magnetic resonance (MR) imaging (MRI) when applied to MR-guided therapies of abdominal or pelvic organs due to organ shift and deformation. 1,2 MR-guidedfocused ultrasound (MRgFUS) therapy performs noninvasive heat delivery under MR supervision that can provide for accurate targeting and noninvasive temperature measurement for therapy control and verification.…”

“…7,8 In addition, the efficiency of localizing ultrasound energy to the target is reduced due to the target zone moving away from the focus position, necessitating gating or more diffuse treatment zones. 2 As respiration is the main source of abdominal organ motion, compensation techniques for respiratory motion have been proposed and developed to reduce temperature errors in MR thermometry. Most of these studies have designed and used a custom-made respiratory motion phantom to validate their technology.…”

Augmented-reality visualization for improved patient positioning workflow during MR-HIFU therapy

“…2,3 Clinical development has been enabled by integration of magnetic resonance imaging giving guidance to high-intensity focused ultrasound imaging (MR-HIFU), which has shown promising results for pain palliation. [2][3][4] The MR-HIFU technology is currently being used for palliative treatment of bone metastases, as a second-line treatment after unsuccessful radiation therapy and is occasionally used for tumor control. 5 MR-HIFU provides real-time temperature mapping, enabling the visualization of the thermal dose within the targeted tissue and giving a clear indication of the tissue damage.…”