Sunnybrook Research Institute

Meaghan Anne O'Reilly

Kullervo Henrik Hynynen

Lulu Deng

Alec Hughes

Foroohar Foroozan

Ryan Jones

Systems and methods are provided for performing transcranial diagnostic procedures using a transcranial ultrasound transducer array. The array elements are positioned and oriented such that far field regions respectively associated therewith spatially overlap within the brain of a patient. The array elements may be oriented approximately normal to the skull, permitting efficient coupling of ultrasound energy into the brain. The array elements are controlled to generate ultrasound pulses, where the timing of the pulses is controlled, based on registration between the array elements and volumetric image data, such that ultrasound energy is focused at a target within spatially overlapping far fields of the array elements. The transcranial ultrasound transducer array elements may be positioned and oriented relative to the skull such that their respective ultrasound beams are focused within the skull and diverging with the brain.

Systems and methods for performing transcranial ultrasound therapeutic and imaging procedures

A system and method for controlling the delivery of ultrasound energy to a subject is provided. In particular, such a system and method are capable of safely disrupting the blood-brain barrier. Ultrasound energy is delivered to produce cavitation of an ultrasound contrast agent at a selected pressure value. An acoustic signal is acquired following cavitation, from which a signal spectrum is produced. The signal spectrum is analyzed for the presence of harmonics, such as subharmonics or ultraharmonics. When subharmonics or ultraharmonics are present, the pressure value is decreased for subsequent sonications. If a previous sonication resulted in no subharmonics or ultraharmonics being generated, then the pressure value may be increased. In this manner, the blood-brain barrier can be advantageously disrupted while mitigating potentially injurious effects of the sonication.

System and method for controlling focused ultrasound treatment

A system and method for efficiently transmitting and receiving focused ultrasound through a medium, such as bone, is provided. The focal region of the focused ultrasound is iteratively updated to provide an improved focus through the medium. This method may be carried out using a transducer assembly that includes two or more transmit arrays each operating at a different frequency. An initial focus is set and updated by delivering focused ultrasound with a lower frequency transmit array. The phase corrections determined in the first iteration are applied to subsequently higher frequency transmit arrays and received signals, and the process repeated until a desired focus or image resolution is achieved.

System and method for measuring and correcting ultrasound phase distortions induced by aberrating media

Systems and methods for registering pre-operative medical images, such as computed tomography ('CT') images, to the coordinate space of an ultrasound treatment system are provided. The registration is generally based on minimizing distances between locations associated with an anatomical feature, as identified from the medical images, and spherical surfaces defined by time-of-flight measurements for ultrasound data acquired from the anatomical feature by transducer elements. The locations associated with the anatomical feature, which may be a skull of the subject, can be points or planar surfaces define on the anatomical feature. The registration methods described here can be useful for aberration correction and targeting using an array of high-frequency ultrasound elements. In combination with cavitation monitoring and control, this ultrasound-based registration of CT images could eliminate the need for MRI during these treatments.

Method for registering pre-operative images of a subject to an ultrasound treatment space

Systems and methods for ultrasound imaging capable of achieving spatial resolutions that can resolve objects smaller than 300 &#x3bc;m are described. Ultrasound is transmitted to and steered over a volume-of-interest that contains a microbubble contrast agent to individually excite microbubbles. Signal data is acquired in response to the transmitted ultrasound, and a plurality of images are reconstructed by beamforming the acquired signal data. The spatial resolution of the beamformed images can be further increased using techniques that determine the position of the microbubble within each image to a greater level of accuracy than the point spread function ('PSF') of the ultrasound system. The images can also be combined to produce a single high resolution image of the volume-of-interest using, for instance, a maximum pixel projection technique.

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Meaghan Anne O'Reilly