Dr. Khoa Pham Profile

Dr. Khoa Pham

at University College London

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Publications (4)

Proceedings Article | 13 March 2024 Presentation

A rotating photoacoustic and ultrasound imaging system for whole-body small animal studies

Alissa Silva, Michael Brown, Nam Huynh, Khoa Pham, Edward Zhang, Olumide Ogunlade, Paul Beard, Ben Cox

Proceedings Volume PC12842, PC128420L (2024) https://doi.org/10.1117/12.3008993

KEYWORDS: Ultrasonography, Photoacoustic spectroscopy, Imaging systems, Animals, Acoustics, Wavefront aberrations, Sensors, Biological samples, Biological imaging, Wavefront reconstruction

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Proceedings Article | 9 March 2023 Presentation

A dual-mode photoacoustic and ultrasound imaging system for whole-body small animal studies

Alissa Silva, Edward Zhang, Khoa Pham, Nam Huynh, Michael Brown, Olumide Ogunlade, Paul Beard, Ben Cox

Proceedings Volume PC12379, PC123790J (2023) https://doi.org/10.1117/12.2656074

KEYWORDS: Ultrasonography, Photoacoustic spectroscopy, Imaging systems, Sensors, Acoustics, Wavefront aberrations, Absorption, Ultrasound tomography, Tissues, Photoacoustic tomography

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Proceedings Article | 20 April 2020 Presentation

High resolution 3D photoacoustic scanner for clinical vascular imaging applications (Conference Presentation)

Nam Trung Huynh, Olivia Francies, Katerina Soteriou, Thomas Allen, Khoa Pham, Sacha Noimark, Semyon bodian, Adrien Desjardins, Jiaqi Zhu, Oshaani Abeyakoon, Filip Kuklis, Edward Zhang, Ben Cox, Andrew Plumb, Paul Beard

Proceedings Volume 11240, 1124003 (2020) https://doi.org/10.1117/12.2549559

KEYWORDS: 3D scanning, Photoacoustic spectroscopy, Laser scanners

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Proceedings Article | 4 March 2019 Presentation

Dual mode photoacoustic and ultrasound imaging system based on a Fabry-Perot scanner (Conference Presentation)

Khoa Pham, Sacha Noimark, Nam Trung Huynh, Edward Zhang, Adrien Desjardins, Ben Cox, Paul Beard

Proceedings Volume 10878, 1087826 (2019) https://doi.org/10.1117/12.2506922

KEYWORDS: Scanners, Imaging systems, Photoacoustic spectroscopy, Ultrasonography, Fabry–Perot interferometers, 3D image processing, Tissues, Laser scanners, 3D scanning, In vivo imaging

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Compared to piezoelectric based photoacoustic (PA) scanners, the planar Fabry-Perot (FP) scanner has several advantages. It can provide small element size with high sensitivity, a smooth broadband frequency response, and is transparent to excitation light. This enables the FP scanner to provide excellent high-resolution in vivo PA images of soft tissue to depths up to approximately 10 mm. However, unlike piezoelectric scanners, the FP scanner in its current form cannot provide a pulse-echo ultrasound (US) as well as a PA image, which is useful because of the additional tissue contrast it provides. To address this, a dual mode FP scanner-based system that, for the first time, can acquire co-registered 3D PA and US images has been developed. In order to provide an optical US generation capability, the FP ultrasound sensor was coated with a novel Gold-Nanoparticle-PDMS composite which was excited with nanosecond laser pulses to generate plane wave US pulses. By modifying the FP sensor in this way, it now acts as an US transmitter as well as a receiver. The coating is highly absorbing at the US generation wavelength (>95%) but transparent at the PA excitation wavelength, the latter to allow the system to also operate in PA imaging mode as before. The generated US pulses exhibited peak pressures in the MPa range, which is comparable to the output of conventional piezoelectric based medical US scanners. The pulses had a broad bandwidth (>40 MHz) and the emitted wavefront was planar to within λ/10 at 10 MHz. PA and pulse-echo US signals were mapped in turn by the FP scanner over centimetre scale areas with a step size of 100 μm and an element size of 64 μm. The -3dB bandwidth of the FP sensor was 30 MHz. Reconstruction methods using a k-space formulation recovered co-registered 3D PA and US images. The system’s lateral spatial resolution was evaluated by imaging a line target at depths up to 10 mm and ranged between 50 and 120 μm for both modes. Arbitrarily shaped 3D objects were imaged to demonstrate the volumetric US imaging capability of the scanner. Tissue mimicking phantoms, with impedance mismatches representative of soft tissues, and ex vivo tissue samples were imaged with the system as well as a conventional clinical US scanner for comparison. Finally, the system obtained promising high-resolution 3D dual mode PA-US images for a variety of phantoms with contrast based on both optical absorption and acoustic impedance. This novel all-optical system has the potential to add complementary morphological contrast to photoacoustic vascular images which could aid the clinical assessment of superficial tumours, lymph node disease and other conditions.

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