arXiv subjects

Geng Ku

Publications and source records attributed to Geng Ku.

3 recordsLinked to original sources

arXiv2024

De-aberration for transcranial photoacoustic computed tomography through an adult human skull

Noninvasive transcranial photoacoustic computed tomography (PACT) of the human brain, despite its clinical potential as a complementary technology to functional MRI, remains impeded by the acoustic distortion induced by the human skull. The distortion, which is attributed to the markedly different material properties of the skull relative to soft tissue, results in heavily aberrated PACT images -- a problem that has remained unsolved for the past two decades. Herein, we report the first successful experimental demonstration of the de-aberration of PACT images through an ex-vivo adult human skull using a homogeneous elastic model for the skull. Using only the geometry, position, and orientation of the skull, we faithfully de-aberrate the PACT images of light-absorbing phantoms acquired through an ex-vivo human skull for different levels of phantom complexity and positions. We also demonstrate the generality of our results by attaining a similar extent of de-aberration through a second ex-vivo human skull. Our work addresses the longstanding challenge of skull-induced aberrations in transcranial PACT and advances the field towards unlocking the full potential of transcranial human brain PACT.

physics.med-ph↗

arXiv2023

Whole Cross-Sectional Human Ultrasound Tomography

Ultrasonography is a vital component of modern clinical care, with handheld probes routinely used for diagnostic imaging and procedural guidance. However, handheld ultrasound imaging is limited by factors such as the partial-cross-sectional field of view, operator dependency, contact-induced distortion, and lack of transmission contrast. Here, we demonstrate a new system enabling whole cross-sectional ultrasound tomography of humans in reflection and transmission modes. We generate 2D images of the entire in vivo human cross-section with uniform in-plane resolution using a custom 512-element circular ultrasound receiver array and a rotating ultrasonic transmitter. We demonstrate this technique in regions such as the abdomen and legs in healthy volunteers. To address unmet clinical needs, we explore two key applications. First, we readily observe abdominal adipose distributions in our images, enabling adipose thickness assessment over the body without ionizing radiation or mechanical deformation. Second, we demonstrate an approach for video-rate (30 frame-per-second) biopsy needle localization with respect to internal tissue features. These capabilities make whole cross-sectional ultrasound tomography a potential practical tool for clinical needs not currently met by other modalities.

physics.med-ph↗

arXiv2017

Laser Streaming: Turning a Laser Beam into a Flow of Liquid

Transforming a laser beam into a mass flow has been a challenge both scientifically and technologically. Here we report the discovery of a new optofluidics principle and demonstrate the generation of a steady-state water flow by a pulsed laser beam through a glass window. In order to generate a flow or stream in the same path as the refracted laser beam in pure water from an arbitrary spot on the window, we first fill a glass cuvette with an aqueous solution of Au nanoparticles. A flow will emerge from the focused laser spot on the window after the laser is turned on for a few to tens of minutes, the flow remains after the colloidal solution is completely replaced by pure water. Microscopically, this transformation is made possible by an underlying plasmonic nanoparticle-decorated cavity which is self-fabricated on the glass by nanoparticle-assisted laser etching and exhibits size and shape uniquely tailored to the incident beam profile. Hydrophone signals indicate that the flow is driven via acoustic streaming by a long-lasting ultrasound wave that is resonantly generated by the laser and the cavity through the photoacoustic effect. The principle of this light-driven flow via ultrasound, i.e. photoacoustic streaming by coupling photoacoustics to acoustic streaming, is general and can be applied to any liquids, opening up new research and applications in optofluidics as well as traditional photoacoustics and acoustic streaming.

physics.flu-dyn↗