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Blood transports nutrients to organs and extracts waste products to maintain bodily functions. In physiology, the activities or changes related to blood flow are termed hemodynamics. Hemodynamics are regulated tightly to satisfy metabolic demands and maintain homeostasis. Altered blood flow can indicate the presence and progression of various diseases. Thus, hemodynamic measurements can offer diagnostic and prognostic information. Wide-field optical imaging (WFOI) is non-contact, non-radiative, and high-resolution imaging that is well suited for imaging superficial tissues such as skin or exposed brain. Despite its benefits, WFOI has limitations, such as shallow imaging depth and challenges in the proper interpretation of the measured data due to confounding factors associated with optical absorption and scattering by tissue constituents unrelated to blood. This research focused on two WFOI modalities: laser speckle imaging (LSI) and spatial frequency domain imaging (SFDI). LSI measures blood flow and SFDI measures scattering-independent chromophore (i.e., hemoglobin) concentrations. The confounding problems in these modalities are identified and solutions proposed for skin and brain imaging applications.Chapter 1 emphasizes the importance of considering epidermal melanin when interpreting SFDI data from the skin. We found that skin pigmentation can adversely affect optical measurements, especially scattering parameters, when an improper assumption is used during data processing. We further linked these effects to colorimetric measurements of melanin. The results collectively highlight the need for a better light transport model to handle the thin melanin layer and improve SFDI measurement accuracy.Chapter 2 focuses on how optical properties affect WFOI of cerebral hemodynamics. We created a system combining LSI with SFDI for widefield neuroimaging. A mathematical model derived from dynamic light scattering theory was used to correct LSI measurements of cerebral blood flow. This measurement enables direct comparison of blood flow measurements from multiple subjects and at different time points. We applied this imaging method on mice with Alzheimer’s disease (AD) and mid-life hypertension to study their cerebral hemodynamics and its connection to disease progression. The study aims to identify the connection between vascular health and the progression of AD and whether an antihypertensive treatment can rescue the condition. This is an ongoing study; however, preliminary data suggest that late mid-life hypertension induces dysregulated cerebral hemodynamics in mice with AD pathology when not treated.In summary, the research disseminated in this thesis highlights the need for proper consideration of confounding factors in WFOI of hemodynamics. These findings enable future efforts to improve the accuracy of WFOI measurements.

From the large scale atmospheric turbulent motion to blood flow in microvessels, our daily lives are dependent on various modes of transport phenomena. Different techniques exist that help us to study and understand these complex phenomena experimentally. Flow visualization is one of the most used methods that provide a good qualitative understanding of complex fluid behavior. By definition, flow visualization is the process of making the physics of fluid flows visible. With the development of digital and computational imagery, flow visualization has transitioned from being a qualitative measure to a quantitative measure of transport phenomena. In this research, we have incorporated computational imagery techniques to delineate different scales of transport phenomena such as the flow of convective hot air around a flame and the blood flow inside a mouse’s brain. The visualization was done by generating granular patterns of dark and bright spots, noise, and imposing it on the flow field. For the fire experiments, the granular pattern was created by illuminating a printed noise pattern using white non-coherent light. The hot air around the flame caused fluctuations in air density affecting the air’s refractive index, leading to distortion of the background image. By comparing distorted and undistorted images using optical flow algorithms, the flow field was visualized. A similar algorithm can be deployed to visualize the flow inside a mouse’s brain. Instead of using noncoherent light, the granular pattern was generated by using a laser beam. This granular pattern, produced by random interference effects in laser light, is commonly referred to as laser speckle pattern. When the speckle pattern is generated on blood vessels, the flow of blood causes fluctuations in this pattern leading to a blurriness associated with the blood vessel. This blurriness is later processed using computer algorithms which can be correlated to the motion of the red blood cells. This presentation will describe the pipeline for creating flow visualization of these multiscale transport phenomena and relevant results.

Quantitative characterization of blood flow is important to assess acute physiological health and hemodynamic effects of clinical interventions. A critical need exists for a robust device designed to assess blood flow in biomedical applications. Laser Speckle Imaging (LSI) is a wide-field non-invasive optical technique that enables superficial blood flow quantification. A few potential clinical applications of LSI include assessing blood flow during burn patient triaging, quantifying tissue perfusion in a neonatal intensive care unit, and real-time blood flow mapping during surgery. The blood flow information that LSI provides can be helpful for bedside care. However, since LSI systems are highly sensitive to motion, most LSI studies are typically performed using mounted systems. Widespread use of LSI in the clinic has not occurred, in part, due to the bulky form factor and lack of mobility of these systems. Our proposed solution to address the limitations of these mounted systems is a handheld LSI device. Handheld LSI would provide clinicians with objective blood flow measurements in a convenient form factor. However, motion artifact during handheld data acquisition can lead to unreliable and inaccurate blood flow values. Attempts have been made to account for motion artifact noise, but they lack an approach to align (co-register) images. Co-registration is a necessary step prior to the common practice of image averaging to improve the signal-to-noise ratio in producing blood flow maps. Our approach to address both motion artifact and image co-registration for handheld LSI was adding a fiducial marker (FM) into our imaging protocol.We developed a portable, handheld LSI device and a protocol that integrated a FM into the imaging workflow. We automated the processes of sorting frames based on motion artifact and co-registering misaligned images. We compared the performance of the mounted and handheld setups using in vitro flow phantom experiments as a proof-of-concept study. We then demonstrated translation of our imaging protocol into an ongoing in vivo study with a porcine burn wound model.We attempted to further reduce motion artifact by making additional modifications to the handheld LSI device. The modified LSI device was also validated with in vitro flow phantom experiments and in vivo imaging of vessels within a dorsal skinfold window chamber model.In addition to the concerns of motion artifacts for clinical imaging, optical property changes in dynamic wounds or developing tissues may cause inaccuracies in the measured blood flow. We addressed this issue by combining LSI and Spatial Frequency Domain Imaging (SFDI), a non-contact imaging modality used to quantify tissue optical properties, to obtain corrected blood flow values. We then showed the potential errors in blood flow values when optical properties are not properly accounted for in the dynamic wounds of a porcine burn wound model.Collectively, these works demonstrate our attempts at providing a viable alternative for clinical blood flow imaging with our handheld LSI device and imaging protocol and accounting for motion artifact and optical property changes in LSI.

Laser speckle imaging (LSI) is a wide-field optical imaging technique that provides information about the movement of scattering particles in biological samples. LSI is used to create maps of relative blood flow and perfusion in samples such as the skin, brain, teeth, gingiva, and other biological tissues. The presence of static, or non-moving, optical scatterers affects the ability of LSI to provide true quantitative and spatially resolved measurements of blood flow. With in vitro experiments using tissue-simulating phantoms, we determined that temporal analysis of raw speckle image sequences improved the quantitative accuracy of LSI to measure flow beneath a static scattering layer. We then applied the temporal algorithm to assess the potential of LSI to monitor oral health. We designed and tested two generations of miniature LSI devices to measure flow in the pulpal chamber of teeth and in the gingiva. Our preliminary clinical pilot data indicated that speckle contrast may correlate with gingival health. To improve visualization of subsurface blood vessels, we developed a technique called photothermal LSI. We applied a short pulse of laser energy to selectively perturb the motion of red blood cells, increasing the signal from vasculature relative to the surroundings. To study the spectral and depth dependence of laser speckle contrast, we developed a Monte Carlo model of light and momentum transport to simulate speckle contrast. With an increase in the thickness of the overlying static-scattering layer, we observed a quadratic decrease in the quantity of dynamically scattered light collected by the detector. We next applied the model to study multi-exposure speckle imaging (MESI), a method that purportedly improves quantitative accuracy of subsurface blood flow measurements. We unexpectedly determined that MESI faced similar depth limitations as conventional LSI, findings that were supported by in vitro experimental data. Finally, we used the model to study the effects of epidermal melanin absorption on LSI, and demonstrated that speckle contrast is less sensitive to varying melanin content than reflectance. We then proposed a two-wavelength measurement protocol that may enable melanin-independent LSI measurements of blood flow in patients with varying skin types. In conclusion, through in vitro and in silico experiments, we were able to further the understanding of the depth dependent origins of laser speckle contrast as well as the inherent limitations of this technology.

Background and Objectives:Although abnormal blood flow is linked to clinical risk of illness in neonates, clinicians typically do not integrate flow measurements into routine monitoring in the neonatal intensive care unit (NICU). We and other research groups have previously demonstrated the ability of Laser Speckle Imaging (LSI) to measure changes in blood flow in both a laboratory and clinical settings. We postulate that LSI, in a clinic-friendly form factor, can provide important hemodynamic information in the NICU. Here, I describe initial efforts to develop a handheld LSI system and deploy it to University of California, Irvine Medical Center NICU.Study Design/Methods:I designed and fabricated a handheld LSI system based on design principles to insure successful implementation into a clinical setting. Using in-vitro tissue phantom systems, I assessed the system performance of handheld LSI versus a traditional mounted configuration. I collected multi-user data (n=7) to assess the variation in flow measurements attributed to user performance. I collected data from two in-vivo occlusion models to demonstrate that the handheld device can detect both qualitative and quantitative changes in blood flow. Finally, I acquired data from an on-going NICU based clinical study (n=30, to date) in which we collected LSI images of abdomen and the heel over a period of several months.Results:I demonstrate that the handheld nature of the device has little effect on the flow measurement sensitivity via a study that was focused on the characterization of tissue simulating phantoms. Flow phantoms were characterized using both bench top and handheld LSI instruments. I show that measurements of flow from these phantoms is not user dependent based on testing using a pool of 7 minimally trained users. I demonstrate that the handheld LSI system measures trends in flow that are similar to those reported previously using bench top LSI systems during in-vivo occlusion models. I observed up to an 83.9% increase in flow index measured in neonates at the abdomen after feeding, while only up to a 16.1% increase was observed in the heel. Lastly, I observed a statistically significant difference between the maximum range of flow index values measured at the abdomen in necrotizing enterocolitis neonates and a healthy population (P=.015).Conclusion:The handheld LSI system can measure changes in blood flow and is minimally sensitive to errors due to handheld motion. Flow changes found in the abdomen warrant further studies to investigate the feasibility of using the LSI to detect compromised intestinal blood flow in neonates. These results suggest that LSI may be capable of providing additional screening for neonates with suspected gut pathology.

Roughly 400,000 children each year are born with port wine stain (PWS) birthmarks, which are skin capillary malformations characterized by a pink-reddish color that develop into purple nodules if left untreated. While PWS birthmarks can be found anywhere on the body and are typically non-life threatening, a large majority (~90%) present on the head and neck regions and can lead to complications including dental abnormalities and may be associated with capillary malformations in other organs such as the eyes (glaucoma), and brain (seizures). Due to the unsightly nature of PWS, people that have them on exposed areas of skin (face, neck, arm or leg regions) can endure immense psychological and social suffering. The current gold standard treatment for PWS in the US is laser irradiation using the pulsed dye laser (PDL). Treatment of PWS with the PDL has limited efficacy; many patients undergo 15 or more laser treatments without seeing full clearance of the PWS, demonstrating the need to investigate alternative therapies. In my dissertation research, I investigated alternatives to PDL treatment for PWS, including photodynamic therapy (PDT), combined PDT/PDL protocols, and alternative light based treatments. PDT has demonstrated promise towards achieving better treatment outcomes for PWS birthmarks, however, careful selection of treatment parameters is needed to avoid unwanted side effects. I performed preclinical studies of PDT using two photosensitizers, NPe6 and Hemoporfin, to better develop safe treatment parameters. I then investigated a combined PDT/PDL protocol and determined that a synergistic effect exists between the PDT and PDL protocols, illustrating that this combined approach leads to a desired treatment outcome while minimizing side effects. To better understand the PDT treatment mechanisms in skin, I also studied the depth of injury caused by NPe6-mediated PDT in preclinical models and found a direct relationship between depth of vascular injury and light dose administered. Finally, in investigating alternatives to the PDL, I studied the use of intense pulsed light (IPL) and performed a direct comparison study to the PDL. I used computational models to characterize the predicted performance of the IPL and performed experimental studies in preclinical models.

Background The regulation of cerebral blood flow is critical for normal brain functioning, and many physiological and pathological conditions can have long-term impacts on cerebral blood flow. However, minimally invasive tools to study chronic changes in animal models are limited. New method We developed a minimally invasive surgical technique (cyanoacrylate skull, CAS) allowing us to image cerebral blood flow longitudinally through the intact mouse skull using laser speckle imaging. Results With CAS we were able to detect acute changes in cerebral blood flow induced by hypercapnic challenge. We were also able to image cerebral blood flow dynamics with laser speckle imaging for over 100 days. Furthermore, the relative cerebral blood flow remained stable in mice from 30 days to greater than 100 days after the surgery. Comparison with existing methods Previously, achieving continuous long-term optical access to measure cerebral blood flow in individual vessels in a mouse model involved invasive surgery. In contrast, the CAS technique presented here is relatively non-invasive, as it allows stable optical access through an intact mouse skull. Conclusions The CAS technique allows researcher to chronically measure cerebral blood flow dynamics for a significant portion of a mouse’s lifespan. This approach may be useful for studying changes in blood flow due to cerebral pathology or for examining the therapeutic effects of modifying cerebral blood flow in mouse models relevant to human disease.

Transparent “Window to the Brain” (WttB) cranial implants made from a biocompatible ceramic, nanocrystalline Yttria-Stabilized Zirconia (nc-YSZ), were recently reported. These reports demonstrated chronic brain imaging across the implants in mice using optical coherence tomography (OCT) and laser speckle imaging. However, optical properties of these transparent cranial implants are neither completely characterized nor completely understood. In this study, we measure optical properties of the implant using a swept source OCT system with a spectral range of 136 nm centered at 1,300 nm to characterize the group refractive index of the nc-YSZ window, over a narrow range of temperatures at which the implant may be used during imaging or therapy (20–43°C). Group refractive index was found to be 2.1–2.2 for OCT imaging over this temperature range. Chromatic dispersion for this spectral range was observed to vary over the sample, sometimes flipping signs between normal and anomalous dispersion. These properties of nc-YSZ should be considered when designing optical systems and procedures that propagate light through the window, and when interpreting OCT brain images acquired across the window.

While visual assessment by a clinician is the standard of care for burn severity evaluations, new technologies at various stages of development are attempting to add objectivity to this practice by quantifying burn severity. Assessment accuracy generally improves after the burn injury has progressed, but early assessments that correctly identify superficial partial and deep partial burns have the potential to lead to more prompt treatments and shorter recovery times. To date, Spatial Frequency Domain Imaging (SFDI) has only been used in animal models of burns, but has shown the potential to categorize burns accurately at earlier time points. Here we examine the potential for SFDI to assess burn severity in clinical patients. We also utilize Laser Speckle Imaging (LSI), an FDA cleared non-invasive imaging technology that typically measures blood perfusion in order to evaluate burns in clinical patients. We present a case series of two patients, both with partial thickness burns of varying severity. Partial thickness burns are often difficult for clinicians to categorize based on visual appearance alone. SFDI and LSI were both performed on each patient at approximately 24 and 72 h after their respective burn incidents. Each technique was able to render spatially resolved information that enabled improved assessment accuracy for each burn. This represents the first publication of SFDI applied to clinical burn patients after being successfully utilized in animal models, and highlights the potential for SFDI as a feasible tool for the timely categorization of burn severity. Keywords: Burns, Clinical, Humans, Spatial Frequency Domain Imaging, Laser Speckle Imaging

Background Impaired neurological function affects 85% to 90% of cardiac arrest ( CA ) survivors. Pulsatile blood flow may play an important role in neurological recovery after CA . Cerebral blood flow ( CBF ) pulsatility immediately, during, and after CA and resuscitation has not been investigated. We characterized the effects of asphyxial CA on short‐term (CA ) CBF and femoral arterial blood pressure ( ABP ) pulsatility and studied their relationship to cerebrovascular resistance ( CVR ) and short‐term neuroelectrical recovery. Methods and Results Male rats underwent asphyxial CA followed by cardiopulmonary resuscitation. A multimodal platform combining laser speckle imaging, ABP , and electroencephalography to monitor CBF , peripheral blood pressure, and brain electrophysiology, respectively, was used. CBF and ABP pulsatility and CVR were assessed during baseline, CA , and multiple time points after resuscitation. Neuroelectrical recovery, a surrogate for neurological outcome, was assessed using quantitative electroencephalography 90 minutes after resuscitation. We found that CBF pulsatility differs significantly from baseline at all experimental time points with sustained deficits during the 2 hours of postresuscitation monitoring, whereas ABP pulsatility was relatively unaffected. Alterations in CBF pulsatility were inversely correlated with changes in CVR , but ABP pulsatility had no association to CVR . Interestingly, despite small changes in ABP pulsatility, higher ABP pulsatility was associated with worse neuroelectrical recovery, whereas CBF pulsatility had no association. Conclusions Our results reveal, for the first time, that CBF pulsatility and CVR are significantly altered in the short‐term postresuscitation period after CA . Nevertheless, higher ABP pulsatility appears to be inversely associated with neuroelectrical recovery, possibly caused by impaired cerebral autoregulation and/or more severe global cerebral ischemia.

Laser speckle imaging (LSI) is a wide-field, noninvasive optical technique that allows researchers and clinicians to quantify blood flow in a variety of applications. However, traditional LSI devices are cart or tripod based mounted systems that are bulky and potentially difficult to maneuver in a clinical setting. We previously showed that the use of a handheld LSI device with the use of a fiducial marker (FM) to account for motion artifact is a viable alternative to mounted systems. Here we incorporated a handheld gimbal stabilizer (HGS) to produce a motion stabilized LSI (msLSI) device to further improve the quality of data acquired in handheld configurations. We evaluated the msLSI device in vitro using flow phantom experiments and in vivo using a dorsal window chamber model. For in vitro experiments, we quantified the speckle contrast of the FM (K(FM)) using the mounted data set and tested 80% and 85% of K(FM) as thresholds for useable images (K(FM,Mounted,80%) and K(FM,Mounted,85%)). Handheld data sets using the msLSI device (stabilized handheld) and handheld data sets without the HGS (handheld) were collected. Using K(FM,Mounted,80%) and K(FM,Mounted,85%) as the threshold, the number of images above the threshold for stabilized handheld (38 ± 7 and 10 ± 2) was significantly greater (p = 0.031) than for handheld operation (16 ± 2 and 4 ± 1). We quantified a region of interest within the flow region (K(FLOW)), which led to a percent difference of 8.5% ± 2.9% and 7.8% ± 3.1% between stabilized handheld and handheld configurations at each threshold. For in vivo experiments, we quantified the speckle contrast of the window chamber (K(WC)) using the mounted data set and tested 80% of K(WC) (K(WC,Mounted,80%)). Stabilized handheld operation provided 53 ± 24 images above K(WC,Mounted,80%), while handheld operation provided only 23 ± 13 images. We quantified the speckle flow index (SFI) of the vessels and the background to calculate a signal-to-background ratio (SBR) of the window chamber. Stabilized handheld operation provided a greater SBR (2.32 ± 0.29) compared to handheld operation (1.83 ± 0.21). Both the number of images above threshold and SBR were statistically significantly greater in the stabilized handheld data sets (p = 0.0312). These results display the improved usability of handheld data acquired with an msLSI device.

Improving our understanding of brain function requires novel tools to observe multiple physiological parameters with high resolution in vivo. We have developed a multimodal imaging system for investigating multiple facets of cerebral blood flow and metabolism in small animals. The system was custom designed and features multiple optical imaging capabilities, including 2-photon and confocal lifetime microscopy, optical coherence tomography, laser speckle imaging, and optical intrinsic signal imaging. Here, we provide details of the system's design and present in vivo observations of multiple metrics of cerebral oxygen delivery and energy metabolism, including oxygen partial pressure, microvascular blood flow, and NADH autofluorescence.

© 2014 Optical Society of America. Accurate and timely assessment of burn wound severity is a critical component of wound management and has implications related to course of treatment. While most superficial burns and full thickness burns are easily diagnosed through visual inspection, burns that fall between these extremes are challenging to classify based on clinical appearance. Because of this, appropriate burn management may be delayed, increasing the risk of scarring and infection. Here we present an investigation that employs spatial frequency domain imaging (SFDI) and laser speckle imaging (LSI) as non-invasive technologies to characterize in-vivoburn severity. We used SFDI and LSI to investigate controlled burn wounds of graded severity in a Yorkshire pig model. Burn wounds were imaged starting at one hour after the initial injury and daily at approximately 24, 48 and 72 hours post burn. Biopsies were taken on each day in order to correlate the imaging data to the extent of burn damage as indicated via histological analysis. Changes in reduced scattering coefficient and blood flow could be used to categorize burn severity as soon as one hour after the burn injury. The results of this study suggest that SFDI and LSI information have the potential to provide useful metrics for quantifying the extent and severity of burn injuries.

One of the major constraints facing laser speckle imaging for blood-flow measurement is reliable measurement of the correlation time (τC) of the back-scattered light and, hence, the blood's speed in blood vessels. In this Letter, we present a new model expression for integrated speckle contrast, which accounts not only for temporal integration but spatial integration, too, due to the finite size of the pixel of the CCD camera; as a result, we find that a correction factor should be introduced to the measured speckle contrast to properly determine τC; otherwise, the measured blood's speed is overestimated. Experimental results support our theoretical model. © 2014 Optical Society of America.

Alginate encapsulation reduces the risk of transplant rejection by evading immune-mediated cell injury and rejection; however, poor vascular perfusion results in graft failure. Since existing imaging models are incapable of quantifying the vascular response to biomaterial implants after transplantation, in this study, we demonstrate the use of invivo laser speckle imaging (LSI) and wide-field functional imaging (WiFI) to monitor the microvascular environment surrounding biomaterial implants. The vascular response to two islet-containing biomaterial encapsulation devices, alginate microcapsules and a high-guluronate alginate sheet, was studied and compared after implantation into the mouse dorsal window chamber (N=4 per implant group). Images obtained over a 14-day period using LSI and WiFI were analyzed using algorithms to quantify blood flow, hemoglobin oxygen saturation and vascular density. Using our method, we were able to monitor the changes in the peri-implant microvasculature noninvasively without the use of fluorescent dyes. Significant changes in blood flow, hemoglobin oxygen saturation and vascular density were noted as early as the first week post-transplant. The dorsal window chamber model enables comparison of host responses to transplanted biomaterials. Future experiments will study the effect of changes in alginate composition on the vascular and immune responses. © 2013 Elsevier Ltd.

The functionality of vascular networks within implanted prevascularized tissues is difficult to assess using traditional analysis techniques, such as histology. This is largely due to the inability to visualize hemodynamics in vivo longitudinally. Therefore, we have developed dynamic imaging methods to measure blood flow and hemoglobin oxygen saturation in implanted prevascularized tissues noninvasively and longitudinally. Using laser speckle imaging, multispectral imaging, and intravital microscopy, we demonstrate that fibrin-based tissue implants anastomose with the host (severe combined immunodeficient mice) in as short as 20h. Anastomosis results in initial perfusion with highly oxygenated blood, and an increase in average hemoglobin oxygenation of 53%. However, shear rates in the preformed vessels were low (20.8±12.8s-1), and flow did not persist in the vast majority of preformed vessels due to thrombus formation. These findings suggest that designing an appropriate vascular network structure in prevascularized tissues to maintain shear rates above the threshold for thrombosis may be necessary to maintain flow following implantation. We conclude that wide-field and microscopic functional imaging can dynamically assess blood flow and oxygenation in vivo in prevascularized tissues, and can be used to rapidly evaluate and improve prevascularization strategies. © Copyright 2012, Mary Ann Liebert, Inc.

Laser Speckle Imaging (LSI) is fast, noninvasive technique to image particle dynamics in scattering media such as biological tissue. While LSI measurements are independent of the overall intensity of the laser source, we find that spatial variations in the laser source profile can impact measured flow rates. This occurs due to differences in average photon path length across the profile, and is of significant concern because all lasers have some degree of natural Gaussian profile in addition to artifacts potentially caused by projecting optics. Two in vivo measurement are performed to show that flow rates differ based on location with respect to the beam profile. A quantitative analysis is then done through a speckle contrast forward model generated within a coherent Spatial Frequency Domain Imaging (cSFDI) formalism. The model predicts remitted speckle contrast as a function of spatial frequency, optical properties, and scattering dynamics. Comparison with experimental speckle contrast images were done using liquid phantoms with known optical properties for three common beam shapes. cSFDI is found to accurately predict speckle contrast for all beam shapes to within 5% root mean square error. Suggestions for improving beam homogeneity are given, including a widening of the natural beam Gaussian, proper diffusing glass spreading, and flat top shaping using microlens arrays.

During the last three decades, several laser systems, ancillary technologies, and treatment modalities have been developed for the treatment of port wine stains (PWSs). However, approximately half of the PWS patient population responds suboptimally to laser treatment. Consequently, novel treatment modalities and therapeutic techniques/strategies are required to improve PWS treatment efficacy. This overview therefore focuses on three distinct experimental approaches for the optimization of PWS laser treatment. The approaches are addressed from the perspective of mechanical engineering (the use of local hypobaric pressure to induce vasodilation in the laser-irradiated dermal microcirculation), optical engineering (laser-speckle imaging of post-treatment flow in laser-treated PWS skin), and biochemical engineering (light- and heat-activatable liposomal drug delivery systems to enhance the extent of post-irradiation vascular occlusion).

Laser speckle imaging (LSI) is a fast, noninvasive method to obtain relative particle dynamics in highly light scattering media, such as biological tissue. To make quantitative measurements, we combine LSI with spatial frequency domain imaging, a technique where samples are illuminated with sinusoidal intensity patterns of light that control the characteristic path lengths of photons in the sample. We use both diffusion and radiative transport to predict the speckle contrast of coherent light remitted from turbid media. We validate our technique by measuring known Brownian diffusion coefficients (Db) of scattering liquid phantoms. Monte Carlo (MC) simulations of radiative transport were found to provide the most accurate contrast predictions. For polystyrene microspheres of radius 800nm in water, the expected and fit D b using radiative transport were 6:10E-07 and 7:10E-07 mm 2/s, respectively. For polystyrene microspheres of radius 1026 nm in water, the expected and fit Db were 4:7E-07 and 5:35 mm 2/s, respectively. For scattering particles in water-glycerin solutions, the fit fractional changes in Db with changes in viscosity were all found to be within 3% of the expected value. © 2011 Optical Society of America.

Background and Objective: During laser therapy of port wine stain (PWS) birthmarks, regions of perfusionmay persist. We hypothesize that such regions are not readily observable even when laser surgery is performed by highly experienced clinicians. The objective of this study was to use objective feedback to assess the acute vascular response to laser therapy. Study Design/Materials and Methods: A clinic-friendly laser speckle imaging (LSI) instrument was developed to provide the clinician with real-time images of blood flow during laser therapy. Images were acquired from patients undergoing laser therapy of PWS birthmarks at Scripps Clinic and the Beckman Laser Institute and Medical Clinic. Blood flow maps were extracted from the acquired imaging data. Histogram-based analysis was applied in grading the degree of heterogeneity present in the blood flow maps after laser therapy. Results: Collectively, two types of patient responses were observed in response to laser exposure: (1) an immediate increase in perfusion within minutes after laser therapy; and (2) an overall decrease in blood perfusion ∼1 hour after laser therapy, with distinct regions of persistent perfusion apparent in the majority of post-treatment blood-flow images. A comparison of blood flow in PWS and adjacent normal skin demonstrated that PWS blood flow can be greater than, or sometimes equivalent to, that of normal skin. Conclusion: In general, a decrease in skin perfusion is observed during pulsed laser therapy of PWS birthmarks. However, a heterogeneous perfusion map was frequently observed. These regions of persistent perfusion may be due to incomplete photocoagulation of the targeted vessels. We hypothesize that immediate retreatment of these regions identified with LSI, will result in enhanced removal of the PWS vasculature. © 2009 Wiley-Liss, Inc.

Doppler Optical Coherence Tomography (DOCT) imaging of in-vivo retinal blood flow was widely studied as efforts of research community to push this technology into clinic. Spectral Doppler imaging of DOCT has been demonstrated as a quantification method of in-vivo pulsatile retinal blood flow in human eye. This technology has the all the advantages inherited from OCT comparing to Doppler ultrasound. Comparing to normal spatial-distributed color Doppler imaging of DOCT, spectral Doppler imaging can reveal more haemodynamics details on the time dimension. Although resistance index (RI) of a micro-vascular can be measured in vivo from human retina, the clinical significance of RI easurements still needs to be investigated. In vitro experiment conduced with ultrasound has demonstrated the higher vascular resistance value is associated with the higher RI measured assuming the constant compliance of vascular tube. In this study, the rodent window-chamber model (RWCM) was used as a platform to investigate the RI change as the micro-vasculature response to laser irradiation. The higher RI was measured after the occlusion of two veins (should it be arterials) that was verified with laser speckle imaging in our preliminary experiment results. © 2009 SPIE.