Multimodal application of optical ultrasound imaging

1) Brief description of the context of the research including potential impact
Optical ultrasound (OpUS) imaging, where excitation light is converted into ultrasound via the photoacoustic effect, is an emerging alternative to electronic transducer technology. Back-scattered
("pulse-echo") waves are detected using optically resonant structures and reconstructed into images. OpUS imaging probes exhibit broad bandwidths and are readily miniaturised using off-the-shelf fibreoptic components, and are hence ideally suited to image guidance of interventional surgery. Furthermore, OpUS imaging probes can be designed to be insensitive to electromagnetic (EM) interference, thus facilitating concurrent multimodal use in, e.g., MRI or CT scanners. To date, OpUS imaging has been performed using two types of systems. First, highly miniature imaging probes comprising a single source and single receiver were used that were readily integrated into interventional instruments and workflows, but required minutes to hours to acquire an image. Second, a bench-top imaging system was used that achieved video-rate 2D imaging, but required the imaging target to be fully submerged. To improve the clinical practicality of AOUS imaging, a new class of imaging probes is required that can achieve video-rate 2D imaging using a form factor suitable for interventional settings. In this project, fibre-optic technology will be used to develop miniature OpUS probes capable of videorate imaging, which are free from electronics and metals to ensure immunity to EM interference. Ultimately, this will enable concurrent multimodal imaging (e.g., MRI+OpUS) using probes compatible with interventional instruments, which will enable and improve image guidance in, e.g., cardiovascular, perinatal and cancer treatment.

2) Aims and Objectives
The project will involve the following aims and objectives:
- Develop a computational model to predict the imaging performance of OpUS probes;
- Use this model to optimise the geometry of an OpUS imaging probe capable of video-rate imaging and initially aimed at external (i.e., non-interventional) applications;
- Fabricate the OpUS imaging probe using rapid prototyping techniques, ensuring immunity to EM interference. Build experimental setup and write acquisition and control scripts;
- Characterise the performance of the imaging probe using phantoms in the lab, and confirm compatibility with MRI and X-ray imaging;
- Perform the first co-registered multimodal OpUS+MRI and OpUS+X-ray imaging of phantoms. Perform human volunteer studies in the lab and/or in an MRI setting;
- Miniaturise the OpUS imaging probe for interventional use, and design packaging for preclinical in vivo delivery;
- Demonstrate multimodal OpUS+X-ray image guidance in a pre-clinical interventional setting.

3) Novelty of Research Methodology
This research will combine the best aspects of the two current OpUS imaging paradigms, and result in the first system capable of video-rate imaging with a form factor suitable for interventional surgery. To achieve optimal performance, a novel simulation framework for OpUS imaging probes will be developed. State-of-the-art rapid prototyping techniques will be used to fabricate the probes. Immunity to EM interference will be achieved through material selection and fibre-optics, culminating in the first demonstration of OpUS imaging in conjunction with MRI and X-ray.

4) Alignment to EPSRC's strategies and research areas
With a primary focus on ultrasound imaging, this research aligns well with the "Medical Imaging" research area. In particular, this research will lead to novel multimodal imaging modalities that will offer substantial benefits over single modalities and conventional electronic ultrasound. In addition, the numerical modelling involved fits well with the "Engineering Design" area.

5) Any companies or collaborators involved : GOSH: Prof V. Muthurang, Dr J. Steeden & QMUL: Dr M Finlay