Therapeutic apparatus and method for heating a subject
Inventors
Partanen, Ari Ilkka Mikael • Dreher, Matthew Robert • Yarmolenko, Pavel Sergeyevich • Viitala, Antti Johannes • Enholm, Julia Kristina • Kohler, Max Oskar
Assignees
Profound Medical Inc • National Institutes of Health NIH
Publication Number
US-10099069-B2
Publication Date
2018-10-16
Expiration Date
2031-10-11
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Abstract
A therapeutic apparatus (900, 1000) comprising a high intensity focused ultrasound system (904) for heating a target zone (940, 1022). The therapeutic apparatus further comprises a magnetic resonance imaging system (902). The therapeutic apparatus further comprises a memory (952) containing machine executable instructions (980, 982, 984, 986, 988, 990) for execution by a processor (944). Execution of the instructions cause the processor to: generate (702, 802) heating commands (964) which cause the high intensity focused ultrasound system to sonicate the subject; repeatedly acquire (704, 804) magnetic resonance data (954) during execution of the heating commands; repeatedly calculate (706, 806) a spatially dependent parameter (970); and repeatedly modify (708, 808) the heating commands in accordance with the spatially dependent parameter such that within the target zone the spatially dependent parameter remains below a first predetermined threshold and above a second predetermined threshold.
Core Innovation
The invention provides a therapeutic apparatus, method, and computer program product for controlled heating of a target zone in a subject using a high-intensity focused ultrasound (HIFU) system combined with a magnetic resonance imaging (MRI) system. The apparatus includes a processor and memory storing machine-executable instructions that generate heating commands to sonicate the subject in accordance with heating trajectories composed of multiple subtrajectories. The system repeatedly acquires magnetic resonance data during sonication, calculates a spatially dependent parameter (such as temperature), and modifies the heating commands based on this parameter to maintain the parameter below a first predetermined threshold and above a second predetermined threshold within the target zone.
The problem addressed by the invention is the limitation of known mild hyperthermia treatments and feedback algorithms, which were incapable of maintaining an elevated temperature range of about 40–45°C for prolonged durations. Whereas prior art, such as known ablative feedback systems, raise temperature to necrotic levels (>55°C) and then allow cooling, mild hyperthermia requires sustained temperature within a narrow range. Previous binary feedback algorithms stopped sonication immediately after reaching thermal thresholds. A new feedback control is required that enables continuous temperature maintenance for clinical applications like drug delivery and radiation sensitization.
The invention solves this by implementing a feedback control system that includes multiple heating subtrajectories, maintaining subtrajectories, and a waiting subtrajectory where no sonication occurs. The processor controls switching between these subtrajectories based on action criteria derived from real-time magnetic resonance thermometry data. This feedback maintains a homogeneous temperature profile within the target zone, allowing continuous mild hyperthermia treatment and enabling clinical benefits such as improved chemotherapy, radiation sensitivity, and controlled drug release. The system further enables flexible trajectory geometries and dynamic adjustment of power and duration during sonication.
Claims Coverage
The patent includes one independent claim for a therapeutic apparatus, one independent claim for a computer program product, and one independent claim for a method, all covering controlled heating of a target zone using MR-guided high intensity focused ultrasound with feedback control.
Controlled heating using spatially dependent feedback
The processor repeatedly acquires magnetic resonance data during sonication and calculates a spatially dependent parameter. It modifies heating commands so that this parameter within the target zone remains between first and second predetermined thresholds, maintaining controlled heating.
Use of heating, maintaining, and waiting trajectories
The heating trajectories include multiple heating subtrajectories, followed by waiting commands that halt sonication for a predetermined time and maintaining commands that sonicate maintaining trajectories composed of maintaining subtrajectories. The system switches sonication based on feedback from the spatially dependent parameter to sustain mild hyperthermia.
Switching criteria to control subtrajectory progression
Sonication switches from a current heating subtrajectory to a subsequent one according to switch criteria including maximum/minimum time, temperature, dose, or signal intensity values. Maintaining subtrajectories are sonicated when the spatially dependent parameter falls below thresholds, with the ability to prioritize among multiple subtrajectories.
Integration with radiation therapy systems
The apparatus may include a radiation therapy system controlled to irradiate a radiation target either during or after heating the target zone, where the radiation target overlaps partially or fully with the heated target zone.
Generation of trajectories based on imaging and treatment plans
The processor receives medical image data and a treatment plan descriptive of the target zone location and generates heating and maintaining trajectories accordingly. Magnetic resonance data is used to reconstruct medical images for this purpose.
Halting sonication based on secondary parameters
Sonication is halted when a predetermined change occurs in a second spatially dependent parameter derived from magnetic resonance data, which allows monitoring of therapy efficacy and safety.
These inventive features collectively provide a closed-loop MR-HIFU therapeutic system that precisely controls mild hyperthermia by dynamically adjusting ultrasonic sonication based on spatially dependent feedback, with modalities for safe and effective treatment confirmed by imaging and optionally integrated with radiation therapy.
Stated Advantages
Provides homogeneous and accurate temperature control in the target zone essential for clinical implementation of mild hyperthermia.
Enables maintenance of elevated temperature within a narrow therapeutic range (40-45°C) for prolonged durations, unlike previous feedback systems.
Increases therapeutic effectiveness by enabling physiological and cellular changes beneficial for chemotherapy, radiation therapy, drug delivery, and gene expression under MR guidance.
Uses a simple, robust binary feedback algorithm that is less complex than parametric feedback algorithms while providing stable control.
Allows real-time adjustments of sonication power, duration, and trajectory geometry, improving treatment flexibility.
Documented Applications
MR-guided pain palliation.
MR-guided radiation sensitization.
MR-guided chemotherapeutic delivery (local drug delivery).
MR-guided drug activation.
MR-guided gene delivery and gene expression.
Inducing physiological and cellular changes under MR guidance for clinical benefits.
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