Speckle contrast imaging is an established technique to obtain relative blood maps over wide field of views. Currently, its most accurate implementation relies on the acquisition of raw speckle images at different exposure times but requires modulation of a laser pulse in duration and intensity and precise synchronization with camera. This complex instrumentation has limited the use of multiple exposure speckle imaging. We evaluate here a simplified approach based on synthetic exposure images created from the sum of successive frames acquired with a 1 ms exposure time. Both methods have been applied to evaluate controlled flows in micro-channels. The contribution of noises to the speckle contrast have been quantified and compared. Dark, readout and shot noise contributions to the total contrast remains constant for modulated exposure, while all these contributions decrease with increasing exposure time for synthetic exposure. The relative contribution of noises to speckle contrast depends on the level of illumination, the exposure time and the flows that are imaged. Guidelines for accurate flow measurements in the synthetic exposure acquisition scheme are provided. The synthetic exposure method is simple to implement and should facilitate the translation of multiple exposure speckle imaging to clinical setups .
Random matrix theory provides new insights into multiple scattering in random media. In a recent study, we demonstrated the statistical separation of single- and multiple-scattering components based on a Wishart random matrix. The first- and second-order moments were estimated through a Wishart random matrix constructed using dynamically-backscattered speckle images. In this study, this new strategy was applied to laser speckle contrast imaging (LSCI) of in-vivo blood flow. The random matrix-based method was adapted and parameterized using electric field Monte Carlo simulations and in-vitro bl…
We present an intensity speckle simulation algorithm based on stochastic differential equations. Intensity speckles are generated with a negative exponential distribution and an exponential auto-correlation decay. The mean of the distribution is spatially varying dictated by photon diffusion to take into account of diffuse speckles. The algorithm is validated using simulation studies for both surface and deep tissue blood flow with potential applications in diffuse correlation spectroscopy.
Infrared light scattering methods have been developed and employed to non-invasively monitor human cerebral blood flow (CBF). However, the number of reflected photons that interact with the brain is low when detecting blood flow in deep tissue. To tackle this photon-starved problem, we present and demonstrate the idea of interferometric speckle visibility spectroscopy (ISVS). In ISVS, an interferometric detection scheme is used to boost the weak signal light. The blood flow dynamics are inferred from the speckle statistics of a single frame speckle pattern. We experimentally demonstrated the i…
We investigated a new optical approach for the detection of the coagulation dynamic process by means of the information on the optical vortex. In our study, laser speckle was captured using a high-speed CMOS camera, and the statistical information of the optical vortex characterized the change in coagulation properties with time. Similar to the scattering particles, the motion of the optical vortex is restricted during coagulation, as a result, the whole process of coagulation can be detected by calculating the mean square displacement(MSD) of the optical vortex. The results demonstrate a clos…
Thermal cooling mechanisms of human exposed to electromagnetic (EM) radiation are studied in detail. The electromagnetic and thermal co-simulation method is utilized to calculate the electromagnetic and temperature distributions. Moreover, Pennes' bioheat equation is solved to understand different thermal cooling mechanisms including blood flow, convective cooling and radiative cooling separately or jointly. Numerical results demonstrate the characteristics and functions for each cooling mechanism. Different from the traditional view that the cooling effect of blood is usually reflected by its…
Focused ultrasound stimulated microbubbles have been shown to be capable of inducing blood flow shutdown and necrosis in a range of tissue types in an approach termed antivascular ultrasound or mechanical ablation. In oncology, this approach has demonstrated tumor growth inhibition, and profound synergistic antitumor effects when combined with traditional platforms of chemo, radiation and immune therapies. However, the exposure schemes employed have been broad and underlying mechanisms remain unclear with fundamental questions about exposures, vessel types and sizes involved, and the nature of…
Denoising method for dynamic contrast-enhanced CT perfusion studies using three-dimensional deep image prior as a simultaneous spatial and temporal regularizer
Multi-contrast laser endoscopy for in vivo gastrointestinal imaging
Department of Biomedical Engineering（生物医学工程系）；Johns Hopkins University（约翰霍普金斯大学）；Division of Gastroenterology and Hepatology（消化内科与肝病科）；Johns Hopkins Hospital（约翰霍普金斯医院）
