Wonseok Choi

For decades now, photoacoustic imaging (PAI) has been investigated to realize its potential as a niche biomedical imaging modality. Despite its highly desirable optical contrast and ultrasonic spatiotemporal resolution, PAI is challenged by such physical limitations as a low signal-to-noise ratio (SNR), diminished image contrast due to strong optical attenuation, and a lower-bound on spatial resolution in deep tissue. In addition, contrast-enhanced PAI has faced practical limitations such as ins

Background Monitoring the microcirculation in human feet is crucial in assessing peripheral vascular diseases, such as diabetic foot. However, conventional imaging modalities are more focused on diagnosis in major arteries, and there are limited methods to provide microvascular information in early stages of the disease. Purpose To investigate a three-dimensional (3D) noncontrast bimodal photoacoustic (PA)/US imaging system that visualizes the human foot morphologically and also reliably quantif

This article offers a perspective on photoacoustic tomography (PAT) under realistic scenarios. While PAT has gained much attention in preclinical and clinical research, most early works used image reconstruction techniques based on ideal assumptions, and thus these techniques may not be fully effective in real environments. In this work, we consider such non-ideal conditions as a limited view, limited bandwidth, lossy medium, or heterogeneous medium. More importantly, we use k-Wave simulation to

We propose soft combining methods for cooperative spectrum sensing in cognitive radio networks over fast-fading channels. In fast-fading environment, it is difficult to obtain the exact probability distribution of the total received energy during an observation period. Therefore, we apply the mixture of gamma (MoG) approximation to obtain the distribution function of the total received energy. By exploiting the approximated distribution, we derive a soft combining method that reduces the probabi

Photoacoustic (PA) imaging has gained much attention, providing structural and functional information in combination with clinical ultrasound (US) imaging systems. 2D PA and US imaging is easily implemented, but its heavy dependence on operator skills makes 3D imaging preferable. In this study, we propose a panoramic volumetric clinical PA and US imaging system equipping a handheld imaging scanner weighing 600 g and measuring 70 × 62 × 110 mm³. Multiple PA/US scans were performed to c

Photoacoustic imaging is a promising medical imaging modality that enables the visualization of molecular functional and morphological information of biological tissues. Its clinical potential has been widely investigated for assessing and diagnosing various diseases. Currently, several research groups are developing photoacoustic imaging systems for translation from the laboratory to the clinic. In particular, the integration of photoacoustic imaging into existing diagnostic ultrasound applicat

Vitiligo needs early identification for proper intervention. Current adjunct diagnostic methods rely mostly on subjective visual inspection. Thus, identification of early or atypical vitiligo lesions among other hypopigmentation disorders may pose challenges. To overcome this, we investigate the feasibility of a three-dimensional (3D) photoacoustic (PA) and ultrasound (US) imaging technique as a new adjuvant analytic tool providing quantitative characterization of hypopigmentation features. This

This minireview highlights the recent advances in the therapeutic agents that aim to provide synergistic enhancements of focused ultrasound treatment of tumors. Even though focused ultrasound therapy itself can bring therapeutic effects in cancers, many biochemical agents have been reported in the literature to enhance the treatment efficacy significantly. Until now, many mechanisms have been researched to advance the therapy, such as sonodynamic-plus-chemo-therapy, microbubble-aided therapy, lo

We introduce a fast Nearest Neighbor Search (NNS) algorithm using an Approximate Cached k-d tree (ACk-d tree) structure for low dimensional data sets. The search process of the standard k-d tree starts from the root node and employs a tentative back-tracking search. In contrast, the proposed method begins to search at the appropriate leaf node (cached node) and applies a depth-first nontentative search. This method improves searching speed, with tradeoff of the searching accuracy. To get a prope

Alzheimer's disease is one of the most critical brain diseases. The prevalence of the disease keeps rising due to increasing life spans. This study aims to examine the use of hemodynamic signals during hypoxic respiratory challenge for the differentiation of Alzheimer's disease (AD) and wild-type (WT) mice. Diffuse optical spectroscopy, an optical system that can non-invasively monitor transient changes in deoxygenated (ΔRHb) and oxygenated (ΔOHb) hemoglobin concentrations, was used to monitor h

We have developed surface-crosslinked polymer nanodroplets having capabilities of therapeutic enhancement for high intensity focused ultrasound (HIFU) treatment and image guidance by photoacoustic (PA) and ultrasound (US) imaging. Six-arm-branched poly(ethylene glycol) (PEG) is crosslinked with Pluronic F127 mixed with naphthalocyanine (Nc), and sonicated with liquid perfluorohexane (PFH) to form nanoparticles encapsulating Nc and PFH (Nc/PFH@PCPN). The Nc dye provides high optical absorption at

We demonstrate an agent-free multi-structural peripheral angiography technique based on the volumetric photoacoustic (PA) and ultrasound (US) images. The volumetric images are obtained by stacking B-mode PA/US images along the elevational direction using a motorized scanner. Three structural features such as skin, bone, and vasculature are extracted from the volumetric US image and combined with the PA microvasculature image to provide a multi-structural vascular image of the foot. For quantitat

This paper presents a fast Nearest Neighbor Search (NNS) algorithm for geometric data sets, based on a modified k-d tree using the cache technique. First, the tree-based search process of our algorithm starts from an appropriate (cached) leaf node, not from the root node. Initial search space is restricted within small limit around the leaf node and the recursive depth-first tentative search is excluded. Therefore, the length of the node traversal path can be shortened. Second, we developed seve