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Biomedical Imaging and Instrumentation

Biomedical Imaging and Instrumentation - Poster Session E

Poster R14 - Rapid Cranial Contour Measurement Algorithm Based on Phassed-Array Synthetic Aperture

Saturday, October 26, 2024

10:00 AM - 11:00 AM EST

Location: Exhibit Hall E, F & G

Primary Investigator(s)

Ren Ma, Dr (he/him/his)

Associate Researcher
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences
Tianjin, United States

Co-Author(s)

Xiaoqing Zhou

Associate Researcher
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences, United States
Xin Wang

Associate Researcher
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences, United States
Shunqi Zhang

Professor
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences, United States

Presenting Author(s)

Tao Yin, MA

Professor
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences, United States

Last Author(s)

Zhipeng Liu, PhD (she/her/hers)

Professor
Institute of Biomedical Engineering, Chinese Academy of Medical Sciences, United States

Introduction: Transcranial focused ultrasound(tcFUS) technology as an emerging neuromodulation technology has been widely used in neuromodulation and treatment of the deep brain with the advantages of non-invasiveness, high resolution, deep penetration and safety. The heterogeneity of the skull and the great variability of the acoustic parameters are the main reasons for the shift of the actual focal point and the scattering of the focal domain after the focused ultrasound penetrates the skull. In order to solve the aberration issue of focused ultrasound penetration into the skull, most numerical simulations were based on virtual point source time reversal method, medical imaging such as Computed Tomography(CT) or Magnetic Resonance Imaging(MRI) has been used for skull calibration and compensation, which increases the treatment cost of transcranial focused ultrasound technology, so the use of ultrasound to achieve a precise measurement of the skull is a new research direction for tcFUS. In this study, based on the synthetic aperture technique, a phased array transmitted ultrasound signals and received the echo signals reflected from the inner and outer contours of the skull, and the coordinates of the skull contour points were simultaneously calculated to realize the rapid measurement of the skull contour. A real head simulation model and a skull phantom were established to verify the algorithm.

Materials and

Methods: Simulation: The principle of multi-array synthetic aperture is to combine multiple transmitting and receiving arrays to achieve an effective combination of ultrasound signal sources. All the emitting array elements are divided into two groups. Starting from the first array element, every nine array elements are defined as a group. Each group of arrays works as "transmit ultrasound signal - receive echo signal - convert to the next group of arrays". The Hilbert transform is applied to the received signal to obtain an analytical signal and the envelope of the signal is taken. The K-space pseudo-spectral method is used to simulate the ultrasound propagation process in the skull, which is commonly used to solve nonlinear fluctuation equations in the Cartesian coordinate system.
Experiment:Considering the size of the skull model as well as the phased array focusing capability and cost, the ultrasound transmitting device selected in this study is a 64-array linear phased array. Since low-frequency ultrasound has a longer wavelength and is more likely to penetrate the skull to focus on the intracranial brain tissue, the centre frequencies of the emitted ultrasound signals were all 0.5 MHz. The skull and the phased array probe were placed in a homemade watertank with degassed water. The phased-array transducer was fixed 2 cm above the skull phantom, and a marked point was located at the centre of the cranial phantom.The phased-array transducer was aligned by a cross-laser location module, which ensured that the calibration position of the transducer and skull.

Results, Conclusions, and Discussions: The simulation results showed that the maximum detection error of the center area of the outer surface of the skull model was 0.15 mm, and that of the edge area was 0.4 mm. The maximum detection error was 0.3 mm in the center region of the inner surface and 0.5 mm in the edge region. The experimental results showed that the maximum detection error was 0.4 mm in the center area and 0.8 mm in the edge area of the skull surface. The maximum detection error was 0.6 mm in the center area of the inner surface and 0.9 mm in the edge area. The rapid measurement algorithm of skull contour designed in this paper can complete the accurate measurement of the inner and outer contours of the skull within 2 minutes, and the maximum measurement error is controlled within 1 mm. Compared with magnetic resonance imaging (MRI) and computed tomography (CT), it reduces the treatment cost and treatment time, and provides a new method and idea for the next step of adjusting the emission delay of phased array elements to achieve real-time and accurate focusing in the brain.

Acknowledgements (Optional): This research is partially supported by National Natural Science Foundation of China (NSFC) under grant No.81927806.