Research

Cooperatively-Controlled (Co-) Robotic Ultrasound System

Synthetic Tracked Aperture Ultrasound (STRATUS) Imaging

Ultrasonography is a widely used imaging modality to visualize anatomical structures due to its low cost and ease of use; however, it is challenging to acquire acceptable image quality in deep tissue. Synthetic aperture (SA) is a technique used to increase image resolution by synthesizing information from multiple subapertures, but the resolution improvement is limited by the physical size of the array transducer. With a large F-number, it is difficult to achieve high resolution in deep regions without extending the effective aperture size. We propose a method to extend the available aperture size for SA-called synthetic tracked aperture ultrasound (STRATUS) imaging-by sweeping an ultrasound transducer while tracking its orientation and location.

H. K. Zhang, A. Cheng, N. Bottenus, X. Guo, G. E. Trahey, Emad M. Boctor, "Synthetic Tracked Aperture Ultrasound (STRATUS) Imaging: Design, Simulation, and Experimental Evaluation", in Journal of Medical Imaging, 3(2), 027001, 2016

T.-Y. Fang, H. K. Zhang, R. Finocchi, R. H. Taylor, E. M. Boctor, “Force Assisted Ultrasound Imaging System through Dual Force Sensing and Admittance Robot Control”, in International Journal for Computer Assisted Radiology and Surgery (IJCARS), 2017.

N. Bottenus, W. Long, H. K. Zhang, M. Jakovljevic, D. P. Bradway, E. M. Boctor, G. E. Trahey, "Feasibility of Swept Synthetic Aperture Ultrasound Imaging", in IEEE Transactions on Medical Imaging, 35(7), 1676-1685, 2016

H. K. Zhang, T. Y. Fang, R. Finocchi, E. M. Boctor, “High Resolution Three-Dimensional Robotic Synthetic Tracked Aperture Ultrasound Imaging: Feasibility Study”, in SPIE Medical Imaging, 2017.

H. K. Zhang, Rodolfo Finocchi, Kalyna Apkarian, E. M. Boctor, "Co-Robotic Synthetic Tracked Aperture Ultrasound Imag-ing with Cross-Correlation Based Dynamic Error Compen-sation and Virtual Fixture Control", in Proceedings of IEEE International Ultrasonics Symposium (IUS), 2016 (DOI: 10.1109/ULTSYM.2016.7728522)

H. K. Zhang, F. Aalamifar, G. E. Trahey, E. M. Boctor, "In vivo visualization of robotically implemented Synthetic Tracked Aperture Ultrasound (STRATUS) imaging system using curvilinear array", in Proceedings of SPIE Medical Imaging, 9790, 97901X, 2016, San Diego

Photoacoustic Imaging of Cancer

Prostate Specific Membrane Antigen (PSMA)-Targeted Photoacoustic Imaging of Prostate Cancer In Vivo

A sensitive, non-invasive method to detect localized prostate cancer, particularly for repetitive study in patients undergoing active surveillance, remains an unmet need. We propose a photoacoustic (PA) imaging approach by targeting the prostate-specific membrane antigen (PSMA), which is over-expressed in the vast majority of prostate cancers. Through in vivo demonstration on an experiment with mice model, spectroscopic PA imaging can visualize the targeted agent, YC-27, that binds on PSMA+ tumor.

[H. K. Zhang, Y. Chen], J. Kang, A. Lisok, I. Minn, [M. G. Pomper, and Emad M. Boctor], “Prostate Specific Membrane Antigen (PSMA)-Targeted Photoacoustic Imaging of Prostate Cancer In Vivo”, in Journal of Biophotonics, e201800021, 2018, Link.

Photoacoustic Brain Imaging

Listening to Neural Membrane Potential through Photoacoustic Voltage Sensitive Dye

Voltage sensitive dyes (VSD) are designed to monitor membrane potential by detecting fluorescence changes in response to neuronal or muscle electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo systems for external detection. In contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near infrared light excitation and ultrasound detection. In this work, we develop the theoretical concept whereby the voltage-dependent quenching of dye fluorescence leads to a reciprocal enhancement of PA intensity. Based on this concept, we synthesized a novel near infrared photoacoustic VSD (PA-VSD) whose PA intensity change is sensitive to membrane potential. In the polarized state, this cyanine-based probe enhances PA intensity while decreasing fluorescence output in a lipid vesicle membrane model.

H. K. Zhang*, P. Yan*, J. Kang, D. S. Abou, H. N. D. Le, A. K. Jha, D. L. J. Thorek, J. U. Kang, A. Rahmim, D. F. Wong, Emad M. Boctor**, Leslie M. Loew** (*co-first, **co-corresponding author), “Listening to membrane potential: Photoacoustic voltage sensitive dye recording”, in Journal of Biomedical Optics, 22(4), 045006, 2017, PDF.

Single Element Ultrasound Imaging for Lumbar Puncture Guidance

Lumbar punctures (LPs) are interventional procedures used to collect cerebrospinal fluid (CSF), a bodily fluid needed to diagnose central nervous system disorders. Most lumbar punctures are performed blindly without imaging guidance. Because the target window is small, physicians can only accurately palpate the appropriate space about 30% of the time and perform a successful procedure after an average of three attempts. Although various forms of imaging based guidance systems have been developed to aid in this procedure, these systems complicate the procedure by including independent image modalities and requiring image-to-needle registration to guide the needle insertion. Here, we propose a simple and direct needle insertion platform utilizing a single ultrasound element within the needle through dynamic sensing and imaging. The needle-shaped ultrasound transducer can not only sense the distance between the tip and a potential obstacle such as bone, but also visually locate structures by combining transducer location tracking and back projection based tracked synthetic aperture beam-forming algorithm.

H. K. Zhang, Y. Kim, M. Lin, M. Paredes, K. Kannan, A. Moghekar, N. Durr, E. M. Boctor, “Toward dynamic lumbar puncture guidance using needle-based single element ultrasound imaging”, in Journal of Medical Imaging, 5(2), 021224, 2018.

H. K. Zhang, M. Lin, Y. Kim, N. Patel, A. Moghekar, N. Durr, E. M. Boctor, “Toward Dynamic Lumbar Punctures Guidance Based on Single Element Synthetic Tracked Aperture Ultrasound Imaging”, in SPIE Medical Imaging, 2017, Runner-up, Young Scientist Award.

Low-cost Photoacoustic Imaging Using Ultrasound Beamformed Data

Synthetic Aperture Based Photoacoustic Re-beamformer (SPARE)

Photoacoustic (PA) imaging has been developed for various clinical and pre-clinical applications, and acquiring pre-beamformed channel data is necessary to reconstruct these images. However, accessing these pre-beamformed channel data requires custom hardware to enable parallel beamforming, and is available for a limited number of research ultrasound platforms. To broaden the impact of clinical PA imaging, our goal is to devise a new PA reconstruction approach that uses ultrasound post-beamformed radio frequency (RF) data rather than raw channel data, because this type of data is readily available in both clinical and research ultrasound systems. In our proposed Synthetic-aperture based photoacoustic re-beamforming (SPARE) approach, post-beamformed RF data from a clinical ultrasound scanner are considered as input data for an adaptive synthetic aperture beamforming algorithm. When receive focusing is applied prior to obtaining these data, the focal point is considered as a virtual element, and synthetic aperture beamforming is implemented assuming that the photoacoustic signals are received at the virtual element.

H. K. Zhang, M. Bell, X. Guo, H. J. Kang, Emad M. Boctor, "Synthetic-aperture based photoacoustic re-beamforming (SPARE) approach using beamformed ultrasound data", in Biomedical Optics Express, 7(8), 3056-3068, 2016

H. K. Zhang, X. Guo, B. Tavakoli, E. M. Boctor, "Photoacoustic Imaging Paradigm Shift: Towards Using Vendor-Independent Ultrasound Scanners", in Medical Image Computing and Computer-Assisted Intervention (MICCAI), 9900, 585-592, 2016

H. K. Zhang, H. Huang, L. Chen, Y. Kim, E. M. Boctor, “Software-based Approach Toward Vendor-Independent Real-time Photoacoustic Imaging Using Ultrasound Beamformed Data”, in Proceedings of SPIE Photonics West BiOS, 2017.

H. K. Zhang, X. Guo, H. J. Kang, and E. M. Boctor, "Photoacoustic image reconstruction from ultrasound post-beamformed B-mode image", in Proceedings of SPIE Photonics West BiOS 2016, 9708, 970837, 2016, San Francisco

Photoacoustic Imaging Using High PRF Laser

Coded Excitation Using Periodic and Unipolar M-sequences (PUM) for Photoacoustic Imaging

Photoacoustic imaging is an emerging imaging technology combining optical imaging with ultrasound. Imaging of the optical absorption coefficient and flow measurement provides additional functional information compared to ultrasound. The issue with photoacoustic imaging is its low signal-to-noise ratio (SNR) due to scattering or attenuation; this is especially problematic when high pulse repetition frequency (PRF) lasers are used. In previous research, coded excitation utilizing several pseudorandom sequences has been considered as a solution for the problem. However, previously proposed temporal coding procedures using Golay codes or M-sequences are so complex that it was necessary to send a sequence twice to realize a bipolar sequence. Here, we propose a periodic and unipolar sequence (PUM), which is a periodic sequence derived from an m-sequence. The PUM can enhance signals without causing coding artifacts for single wavelength excitation. In addition, it is possible to increase the temporal resolution since the decoding start point can be set to any code in periodic irradiation, while only the first code of a sequence was available for conventional aperiodic irradiation.

H. K. Zhang, K. Kondo, M. Yamakawa, T. Tsuyoshi, "Coded Excitation Using Periodic and Unipolar M-sequences for Photoacoustic Imaging and Flow Measurement", in Optics Express, 24(1), 17-29, 2016

H. Zhang, K. Kondo, M. Yamakawa, T. Tsuyoshi, “Simultaneous Multispectral Coded Excitation for Photoacoustic Imaging”, in 2012 IEEE International Ultrasonics Symposium, 2012, Dresden

H. Zhang, K. Kondo, M. Yamakawa, T. Tsuyoshi, "Simultaneous Multispectral Coded Excitation Using Gold Codes for Photoacoustic Imaging", in Jpn. Journal of Applied Physics, Vol.51, No.7, 2012, 07GF03