Time-gated diffuse correlation spectroscopy (TG-DCS) was used in neuro-intensive care settings for monitoring of patients with severe traumatic brain injury. Here, I will present recent results of clinical translation of TG-DCS at the neuro-intensive care unit by implementing measurements at 1064 nm due to high sensitivity of superconducting nanowire single photon detectors. We obtained a significant correlation (ρ = 0.76) between TG-DCS and invasive thermal diffusion flowmetry. We also demonstrate high temporal resolution to obtain pulsatile flow measurements. Overall, the results demonstrate the first clinical translation capability of the TG-DCS system at 1064 nm using a superconducting nanowire single-photon detector.
The mesoscopic scale is between microscopic and macroscopic scales. In life sciences, mesoscopic imaging allows scientists to record, track and study details of biological systems in the context of an organ, body part, or organism. Mesoscopic imaging techniques have been developed for medical and clinical research, such as drug delivery, cancer diagnosis, etc. Especially when combined with novel nanoparticles and organic dyes in the near-infrared spectral regime, the mesoscopic imaging can probe deeper parts of the animal body. Here, we describe a timeresolved mesoscopic imaging approach, which can image deep inside of the whole mouse noninvasively. In addition, it uses the FastFLIM technique to measure the lifetime of the fluorescent probe. Since the lifetime carries information about the probe’s local microenvironment such as temperature, pH, ion concentration, etc., the lifetime imaging map obtained by the FastFLIM-mesoscope allows tracking quantitative dynamics of the probes in the whole animal body. The technique can also be used for quantitative intrinsic NADH metabolism mapping for real time monitoring of mitochondrial function. Here, we will show mesoscopic-scale NADH imaging in an oral cancer model.
For evaluating and optimization of photodynamic therapy (PDT) efficacy, there is a strong need for imaging modalities that can provide (bio)markers fast, frequently and non-invasively. By combining multiple techniques, optical imaging can simultaneously quantify several PDT-response biomarkers including blood flow, oxygenation and photosensitizer (PS) fluorescence concentration during PDT. Additionally, fluorescence imaging can provide high contrast for visualization for PDT planning and dose optimization. I will present monitoring and predicting the PDT response of oral cancer at both preclinical and clinical settings. The results indicate that real-time blood flow measurements can provide useful feedback for PDT optimization in preclinical models, and that multi-parameter analysis of blood flow, PS fluorescence concentration and oxygen saturation can predict the response of oral cancer patients at the operating room. In the final part of the talk, I will present a novel, dual-channel, dual-modal theranostic endoscope that allows imaging, therapeutic light delivery, and light-triggered release of doxorubicin (Dox) from liposomes to optimize chemophotoherapy, the combination of PDT and chemo. The feasibility of noninvasive, continuous monitoring and optimization based on quantitative Dox/PS concentration distributions will be presented in an ovarian cancer model.
Diffuse optical imaging probes deep living tissue enabling structural, functional, metabolic, and molecular imaging. Recently, due to the availability of spatial light modulators, wide-field quantitative diffuse optical techniques have been implemented, which benefit greatly from structured light methodologies. Such implementations facilitate the quantification and characterization of depth-resolved optical and physiological properties of thick and deep tissue at fast acquisition speeds. We summarize the current state of work and applications in the three main techniques leveraging structured light: spatial frequency-domain imaging, optical tomography, and single-pixel imaging. The theory, measurement, and analysis of spatial frequency-domain imaging are described. Then, advanced theories, processing, and imaging systems are summarized. Preclinical and clinical applications on physiological measurements for guidance and diagnosis are summarized. General theory and method development of tomographic approaches as well as applications including fluorescence molecular tomography are introduced. Lastly, recent developments of single-pixel imaging methodologies and applications are reviewed.
This study investigated whether diffuse optical spectroscopy (DOS) measurements could assess clinical response to photodynamic therapy (PDT) in patients with head and neck squamous cell carcinoma (HNSCC). In addition, the correlation between parameters measured with DOS and the crosslinking of signal transducer and activator of transcription 3 (STAT3), a molecular marker for PDT-induced photoreaction, was investigated. Thirteen patients with early stage HNSCC received the photosensitizer 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a (HPPH) and DOS measurements were performed before and after PDT in the operating room (OR). In addition, biopsies were acquired after PDT to assess the STAT3 crosslinking. Parameters measured with DOS, including blood volume fraction, blood oxygen saturation (StO2), HPPH concentration (cHPPH), HPPH fluorescence, and blood flow index (BFI), were compared to the pathologic response and the STAT3 crosslinking. The best individual predictor of pathological response was a change in cHPPH (sensitivity=60%, specificity=100%), while discrimination analysis using a two-parameter classifier (change in cHPPH and change in StO2) classified pathological response with 100% sensitivity and 100% specificity. BFI showed the best correlation with the crosslinking of STAT3. These results indicate that DOS-derived parameters can assess the clinical response in the OR, allowing for earlier reintervention if needed.
Diffuse reflectance spectroscopy (DRS) is a common technique for assessing tissue optical parameters (absorption,
scattering) non-invasively. However, choosing the correct model for light-tissue interaction is needed for accurate
quantification. The diffusion approximation is only valid for certain ranges of tissue optical properties and specific probe
geometries. For improved quantification with DRS over a wide range of optical properties and for a short source detector
separation, a probe-specific light transport model can provide more accurate analysis of optical parameters. We
developed and tested a probe-specific empirical model by using tissue simulating phantoms with promising results. We
will apply it for the analysis of patients from a clinical trial for head and neck cancer.
PDT has become a treatment of choice especially for the cases with multiple sites and large areas. However, the efficacy
of PDT is limited for thicker and deeper tumors. Depth and size information as well as vascularity can provide useful
information to clinicians for planning and evaluating PDT. High-resolution ultrasound and photoacoustic imaging can
provide information regarding skin structure and vascularity. We utilized combined ultrasound-photoacoustic
microscopy for imaging a basal cell carcinoma (BCC) tumor pre-PDT and the results indicate that combined ultrasound-photoacoustic
imaging can be useful tool for PDT planning by providing both structural and functional contrasts.
Photodynamic Therapy (PDT) has proven to be an effective treatment option for nonmelanoma skin cancers. The ability
to quantify the concentration of drug in the treated area is crucial for effective treatment planning as well as predicting
outcomes. We utilized spatial frequency domain imaging for quantifying the accurate concentration of protoporphyrin IX
(PpIX) in phantoms and in vivo. We correct fluorescence against the effects of native tissue absorption and scattering
parameters. First we quantified the absorption and scattering of the tissue non-invasively. Then, we corrected raw
fluorescence signal by compensating for optical properties to get the absolute drug concentration. After phantom
experiments, we used basal cell carcinoma (BCC) model in Gli mice to determine optical properties and drug
concentration in vivo at pre-PDT.
Photodynamic therapy (PDT) has recently emerged as a potential treatment alternative for head and neck cancer. There is
strong evidence that imprecise PDT dosimetry results in variations in clinical responses. Quantitative tools are likely to
play an essential role in bringing PDT to a full realization of its potential benefits. They can provide standardization of
site-specific individualized protocols that are used to monitor both light and photosensitizer (HPPH) dose, as well as the
tissue response for individual patients. To accomplish this, we used a custom instrument and a hand-held probe that
allowed quantification of blood flow, blood volume, blood oxygen saturation and drug concentration.
We report the tomographic imaging of a photodynamic therapy (PDT) photosensitizer, 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH) in vivo with time-domain fluorescence diffuse optical tomography (TD-FDOT). Simultaneous reconstruction of fluorescence yield and lifetime of HPPH was performed before and after PDT. The methodology was validated in phantom experiments, and depth-resolved in vivo imaging was achieved through simultaneous three-dimensional (3-D) mappings of fluorescence yield and lifetime contrasts. The tomographic images of a human head-and-neck xenograft in a mouse confirmed the preferential uptake and retention of HPPH by the tumor 24-h post-injection. HPPH-mediated PDT induced significant changes in fluorescence yield and lifetime. This pilot study demonstrates that TD-FDOT may be a good imaging modality for assessing photosensitizer distributions in deep tissue during PDT monitoring.
Photodynamic treatment of subcutaneously implanted Colon 26 tumors in BALB/c mice using the aminolevulinic acid
(ALA)-induced photosensitizer protoporphyrin IX (PpIX) was shown to be enhanced by the addition of the vascular
disrupting agent 5,6-Dimethylxanthenone-4-acetic-acid (DMXAA; Novartis ASA404). DMXAA increases vascular
permeability and decreases blood flow in both murine and human tumors. Sufficiently high parenteral DMXAA doses
can lead to tumor collapse and necrosis. We have previously reported marked enhancement of antitumor activity when
PDT, using either Photofrin or HPPH, is combined with low-dose intraperitoneal DMXAA. We now describe the first
attempt to combine topically-applied DMXAA with PDT. For this, DMXAA was applied two hours before PpIX-activating
light delivery. PDT with ALA-PDT alone (ALA 20%; 80 J/cm2 delivered at 75 mW/cm2) caused a 39%
decrease in tumor volume compared to unirradiated controls. Addition of topical DMXAA to ALA-PDT resulted in a
74% reduction in tumor volume. Diffuse correlation spectroscopy (DCS), a non-invasive blood flow imaging method, is
being used to understand the mechanism of this effect and to aid in the proper design of the therapy. For instance, our
most recent DCS data suggests that the 2-hour interval between the DMXAA and light applications may not be optimum.
This preliminary study suggests a potential role for topical DMXAA in combination with PDT for dermatologic tumors.
We constructed a whole-body fluorescence tomography instrument to monitor novel bifunctional phototherapeutic drugs (e.g., HPPH-Cyanine dye conjugate) in small animals. The instrument allows dense source and detector sampling with a fast galvo scanner and a CCD detector for improved resolution and sensitivity (Patwardhan et al., 2005). Here we report tissue phantom measurements to evaluate the imaging performance with a newly constructed tomography instrument. Phantom measurements showed that strong fluorescence generated by HPPH-Cyanine dye (HPPH-CD), having high fluorescence quantum yield and long wavelength fluorescence emission, allowed deep tissue imaging. We also report in vivo fluorescence measurements of the conjugate in Nude mice bearing A549 human non-small cell lung carcinoma (NSCLC) tumors at 24 hr post injection to evaluate tumor detection ability of the conjugate. Our results indicate that the HPPH-CD shows preferential uptake in tumors compared to surrounding normal tissue at 24 hr post injection. This study demonstrates a potential use of HPPH-CD in detection (fluorescence imaging) and treatment (PDT) of deeply seated tumors.
Photodynamic therapy (PDT) using topical aminolevulinic acid (ALA) is currently used as a clinical treatment for
nonmelanoma skin cancers. In order to optimize PDT treatment, vascular shutdown early in treatment must be identified
and prevented. This is especially important for topical ALA PDT where vascular shutdown is only temporary and is not
a primary method of cell death. Shutdown in vasculature would limit the delivery of oxygen which is necessary for
effective PDT treatment. Diffuse correlation spectroscopy (DCS) was used to monitor relative blood flow changes in
Balb/C mice undergoing PDT at fluence rates of 10mW/cm2 and 75mW/cm2 for colon-26 tumors implanted
intradermally. DCS is a preferable method to monitor the blood flow during PDT of lesions due to its ability to be used
noninvasively throughout treatment, returning data from differing depths of tissue. Photobleaching of the photosensitizer
was also monitored during treatment as an indirect manner of monitoring singlet oxygen production. In this paper, we
show the conditions that cause vascular shutdown in our tumor model and its effects on the photobleaching rate.
Indocyanine Green (ICG) is currently the only FDA-approved contrast agent suitable for imaging tumor vascularity
and performing permeability measurements. However, it is non-specific; clearance (wash-out) by the liver
is very rapid, and tumor to normal tissue contrast is not optimal for medical imaging applications. Therefore,
new ICG derivatives are being developed with improved affinity tumor cell affinity, and prolonged circulation
times.1 Furthermore, several new contrast agents (molecular beacons) with specific tumor targeting have been
reported. Tumor cells over-express certain receptors which results in an increased uptake of ligands specific to
those receptors. Chemical conjugation of molecular beacons to such ligands allows for accumulation of the agents
specifically at tumor cites. For example, Weissleder et al.2 have developed protease-activated molecular beacons
that achieved a 12-fold tumor to normal tissue contrast. New molecular beacons might have direct impact on
therapy monitoring: with higher sensitivity and specificity, one can noninvasively monitor and therapeutically
intervene tumors in their early stages, which should lead to better survival rates.
This pilot study explores the potential of noninvasive diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS) for monitoring early relative blood flow (rBF), tissue oxygen saturation (StO2), and total hemoglobin concentration (THC) responses to chemo-radiation therapy in patients with head and neck tumors. rBF, StO2, and THC in superficial neck tumor nodes of eight patients are measured before and during the chemo-radiation therapy period. The weekly rBF, StO2, and THC kinetics exhibit different patterns for different individuals, including significant early blood flow changes during the first two weeks. Averaged blood flow increases (52.7±9.7)% in the first week and decreases (42.4±7.0)% in the second week. Averaged StO2 increases from (62.9±3.4)% baseline value to (70.4±3.2)% at the end of the second week, and averaged THC exhibits a continuous decrease from pretreatment value of (80.7±7.0) [µM] to (73.3±8.3) [µM] at the end of the second week and to (63.0±8.1) [µM] at the end of the fourth week of therapy. These preliminary results suggest daily diffuse-optics-based therapy monitoring is feasible during the first two weeks and may have clinical promise.
The aim is to evaluate the usefulness of optical blood flow measurements for predicting early tumor response to radiation therapy in patients with head and neck tumors. The results suggest a correlation between tumor blood flow changes with clinical outcome.
Near Infrared Spectroscopy (NIRS) has been widely used in cancer imaging spectroscopy because cancer tissue has more blood volume and less oxygen than normal tissue. The neck squamous cell carcinoma is ideal for our study because it’s a surface mass can be easily feel through the skin. We use a simple homodyne phase modulation system, In-phase and Quadrature Phase (I&Q) Detection system, to study the curative effect of therapy in neck cancer patients. Clinical treatment includes mainly chemical and radiation therapy, both of which alter the blood volume and the oxygenation saturation in cancer tissue. The I&Q detection system is capable of the quantification measurement of those biological changes. In this paper, we will simply introduce the I&Q detection system’s principle and constitution, and mainly explain the analysis of patients’ data.
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