The ability to reconstruct ultrasonic images of internal brain structures (soft tissues and blood vessels) through the human skull bone is, without question, very beneficial for biomedical purposes. While current conventional imaging methods include MRI and CT scans, imaging via ultrasound could lower the diagnosis cost, eliminate the radiation hazards, and result in smaller equipment.
Our “Brain Imaging” research group at the IDIR has been suggesting solutions with an aim of developing a final portable ultrasonic user-friendly transcranial diagnostic device for use by battlefield first responders and emergency crews. The final device should be able to detect and accurately locate the presence of foreign objects in the brain, such as bullets and bone fragments, from the outside; the device would be operational with minimum required training. Generally speaking, the suggested solutions are based on a “matched filtering method”, “harmonic phase conjugation”, and “speckle interferometry”, (the two former being for image reconstructions of the static objects, and the latter for transcranial diagnostic imaging of soft tissues and blood vessels).
The main obstacles known to complicate the ultrasonic approach are the strong absorption and the distortion of the acoustical field by thick, multilayered human skull bones. So far, our team has been able to overcome these obstacles and demonstrate, both theoretically and in simulated experiments, the possibility of high-resolution ultrasonic transcranial imaging.
The following topics describe the status of the project in parts:
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Computational Model:
A computational model for detection through thick scull bones of ultrasonic signals reflected from the internal brain structures and blood vessels has been developed. - Calculation of the Noise Level:
The noise levels of the ultrasonic system have been calculated. - Computer simulations:
Computer simulation imitating of ultrasound propagation through a system of multi-element ultrasonic transducers has been conducted. We also successfully tested performance of the matched filtering and speckle interferometry algorithms on simulated and optical data. The accomplishments include complete theoretical calculations, image processing, and data inversion algorithms for visualization of foreign static and dynamic objects behind thick human skull bones. - Table top imaging system:
A table top ultrasonic imaging system has been assembled and tested. - Skull Phantoms:
A proprietary composite material with acoustic parameters close to those of a real human skull bone has been developed. The ability to perform lab measurements on skull bone phantoms tailored to the experimental needs gives a number of advantages during the imaging system development process. Several phantoms of different shape and surface topography have been fabricated to accommodate a variety of testing scenarios and evaluate the signal processing algorithms at various stages of development. - Prototype of the device:
A prototype of a scanning brain diagnostic device including a compact handheld two-dimensional scanner for ultrasonic testing without a large water tank has been designed and built.