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Emerging Imaging, Affordable Imaging

Affordable light source based photoacoustic endoscopy probes for guiding neurosurgical procedures

Project ID: 2021_040

1st Supervisor: Wenfeng Xia, King’s College London
2nd Supervisor: Sebastien Ourselin, King’s College London
Clinical Champion: Keyoumars Ashkan, King’s College London

Aim of the PhD Project:

  • Develop a highly miniaturised, high-resolution fibre-optic photoacoustic endoscopy probe using cost-effective laser diodes as the excitation source.
  • Validate the developed probe with tissue mimicking phantoms and human tumour tissues.

Project Description / Background:

Gliomas are the most common type of brain tumour with a grade-dependent prognosis. Glioblastomas (grade 4) have a 5-year survival rate of only 2% [1]. Accurately determining the tumour grade is crucial to optimise patient outcome. However, grading accuracy with stereotactic biopsies is currently limited by inaccurate tumour sampling. Due to tumour heterogeneity, the grade may be underestimated, which leads to insufficient treatment [2]. Whilst there have been many recent advances in our understanding of brain tumour pathophysiology, stereotactic biopsies do not allow for tissue to be visualised in real-time, since tissues are extracted based solely on pre-operative imaging data. There is an urgent need for novel imaging modalities which can provide high resolution, real-time molecular and structural contrast to guide tumour biopsies.

Photoacoustic microscopy (PAM) provides cellular-level images of tissue in real-time, with contrast that derives from optical absorption by haemoglobin, lipids, and other chromophores. Utilising excitation light with multiple wavelengths, multispectral PAM images can be acquired to obtain spatial distributions of absorbing chromophores. It is therefore ideally suited to visualise changes in vascular morphology and blood oxygenation that are known to be associated with tumour development. Recently, in a preclinical model, PAM was demonstrated to visualise glioma angiogenesis and hyperoxia: indirect indicators of early-stage tumours [3].

Photoacoustic imaging has been one of the fastest growing biomedical imaging modalities in the last two decades, with promises in several pre-clinical and clinical applications. However, clinical translation of this technology has not been progressed at an expected pace. One of the main reasons for this is the requirement of bulky, slow and expensive laser sources for photoacoustic signal excitation. To accelerate clinical translation and explore opportunities in resource-limited settings, this project aims to develop a highly miniaturised, high-resolution fibre-optic photoacoustic endoscopy probe using cost-effective, high power laser diodes as the excitation source. The clinical potential of the developed probe for guiding neurosurgical procedures will be evaluated with tissue-mimicking phantoms and human tissue samples. The success of this project will lead to a new class of highly miniaturised forward-reviewing optical-resolution photoacoustic endoscopy probes that comprise all-optical components, and importantly, with affordable light sources for excitation.

The project requires a student with a background in engineering/medical physics. Some knowledge of optics / ultrasound would be an advantage.

Figure 1: The effects of undersampling diffusion tensor cardiovascular magnetic resonance data along spiral trajectories and examples of reconstruction using convolutional neural networks.

References:

  1. T. S. Surawicz, et al, Journal of Neuro-oncology, 40(2), 151-160, (1998)
  2. M. J. Glantz, et al., Neurology, 41(11), 1741-1741, (1991)
  3. J. Yao, et al. Journal of Biomedical Optics, 16(7), 076003-076003 (2011)

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