KEYWORDS: Photodynamic therapy, Breast cancer, Tumor growth modeling, Tumors, Surgery, Luminescence, In vivo imaging, Near infrared, Microscopy, Cancer
This conference presentation was prepared for the Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXXI conference at SPIE BiOS 2023.
Diffuse optical spectroscopy is a widely used method for the non-invasive recovery of important biological factors such as tissue oxygenation and total hemoglobin concentration. Frequency domain-diffuse optical spectroscopy improves the accuracy of parameter recovery over continuous wave-diffuse optical spectroscopy by enabling the decoupling of tissue absorption from tissue scattering. However, this comes at the price of increased instrumentation cost and complexity. Here we detail an easy to build, low-cost, and robust frequency domain-diffuse optical spectroscopy system to increase accessibility to this technology along with testing of the system’s stability and accuracy to ensure its applicability for biological measurements.
Extracorporeal membrane oxygenation (ECMO) is an invasive technique that is used for patients that have experienced heart or lung failure. Due to the complex nature of this treatment, neurological injuries such as hypoxic ischemic encephalopathy (HIE) or stroke can occur. Conventional neuroimaging is risky for this patient population and only provides a snapshot in time, so continuous non-invasive bedside neuromonitoring. In this study we plan on monitoring cerebral blood flow using diffuse correlation spectroscopy and neural activity with electroencephalography. Correlating blood flow with neural activity will provide insight into the neurovascular coupling between neurologically injured versus normal patients on ECMO.
Jones fractures of the proximal fifth metatarsal carry a significant risk of nonunion, which greatly increases the burden on patients. A significant reason for this fracture’s poorer outcomes is the lack of blood flow in the region it occurs. We will apply our newly developed co-registered speckle contrast and frequency domain-diffuse optical tomography system to monitor the Jones fracture region in healthy subjects under and over 50 years of age. The information collected will provide baseline data for future fracture healing outcomes research and provide insight into whether the poorer healing outcomes of older individuals are related to baseline hemodynamics.
Jones fractures, which occur in the proximal fifth metatarsal of the foot carry a significant risk of nonunion. Nonunions increase the patient’s financial burden, risk of infection, and may take years to heal completely. Exploiting the fact that a reason for this higher risk of nonunion is inadequate blood supply, we will use diffuse optics to monitor the fracture healing process. We recently developed a speckle contrast optical tomography system which we will combine and co-register with a frequency domain-diffuse optical tomography system. This combination will provide a powerful instrument optimized for monitoring patient risk of nonunion during fracture healing.
Effects of extracorporeal membrane oxygenation (ECMO) treatment is a life saving treatment for patients that undergo cardiac or pulmonary arrest and is increasingly being used in adults. However, some adults develop brain injuries during treatment. Current neuroimaging techniques such as CT and MRI are inaccessible for these patients due to the high risk in moving them. In this study, we use diffuse correlation spectroscopy to non-invasively monitor cerebral blood flow in patients at the bedside during ECMO treatment. Using this data alongside physiological data, indices of cerebral autoregulation are calculated to observe how ECMO affects neurological health.
Diffuse optics are deep-tissue non-invasive monitoring techniques that quantify total hemoglobin concentration, blood oxygen saturation and blood flow. Although many demonstrated that diffuse optics are sensitive to changes induced by neoadjuvant chemotherapy in human with breast cancer, the effects of chemotherapeutic drug type, dose, duration, and timing on longitudinal hemodynamic responses are still not well-established. To investigate these effects, we performed longitudinal monitoring of hemodynamic parameters on syngeneic rodent models of breast cancer treated with various chemotherapeutic drugs often used in the clinic. Various doses and combination were explored based on the clinically equivalent dose and median lethal dose.
The feasibility of the spatial frequency domain imaging (SFDI) for early treatment assessment in a mouse femoral injury model was investigated. For mice with and without treatment, the revascularization process was monitored by SFDI, which provides the total hemoglobin concentration (THC) of the injured bone and surrounding soft tissues. The biomechanical strength of the healed femurs was measured after 4 weeks of healing. The correlation between the SFDI-derived THC and the biomechanical strength will be investigated. Such correlation will be used to develop a prediction model to estimate the bone healing outcome at an early time point.
Even though vascularization is recognized as an important factor in bone healing, there are limitations in terms of assessing vascularization in both preclinical and clinical scenarios. Diffuse optics have a potential to fill this gap by providing deep-tissue, non-invasive, longitudinal monitoring of total hemoglobin concentration, blood oxygen saturation and blood flow. Using rodent models with bone grafts or bone fractures, we will demonstrate the potential to build a prediction model for bone treatment efficacy assessment. In addition, the construction of a multi-modal diffuse optical imager to detect nonunion and monitor treatment in foot fractures will be introduced. Validation studies to compare diffuse optics with gold standard methods will be presented.
Revascularization is required to deliver the factors necessary for bone injury healing to the injury site. Therefore, vascularization is usually monitored to assess the bone healing outcome in preclinical settings. Previously, blood flow changes measured by diffuse correlation tomography have shown the potential to predict the healing outcome of the mouse femoral graft in vivo. To obtain more comprehensive hemodynamic information in addition to blood flow, we adapted spatial frequency domain imaging (SFDI) method to quantify the total hemoglobin concentration and oxygen saturation in the mouse bone graft model.
An in-house SFDI system was built based on a Texas Instrument digital micromirror device (DMD) and a near-infrared camera. The system was tested using a simplified tissue phantom mimicking the mouse hindlimb with a femoral allograft (avascular) implanted. A single time-point measurement for mouse hindlimbs with and without allograft was performed. The SFDI results were compared with traditional contrast agent-mediated micro-CT for validation. Longitudinal measurements are being performed before and weekly after the allograft surgery. The SFDI-derived properties will be related to the biomechanical outcomes of the healed bones.
Preliminary results of tissue phantom experiments showed the capability of SFDI for mapping the absorption and scattering properties of the graft mimicking tube at a 2 mm depth. Since the mouse femur is usually ~1-2 mm under the skin surface, the SFDI technique has the potential for monitoring the vascularization in healing bone grafts.
Nicotinamide has been shown to affect blood flow in both tumor and normal tissues, including skeletal muscle. Intraperitoneal injection of nicotinamide was used as a simple intervention to test the sensitivity of noninvasive diffuse correlation spectroscopy (DCS) to changes in blood flow in the murine left quadriceps femoris skeletal muscle. DCS was then compared with the gold-standard fluorescent microsphere (FM) technique for validation. The nicotinamide dose-response experiment showed that relative blood flow measured by DCS increased following treatment with 500- and 1000-mg / kg nicotinamide. The DCS and FM technique comparison showed that blood flow index measured by DCS was correlated with FM counts quantified by image analysis. The results of this study show that DCS is sensitive to nicotinamide-induced blood flow elevation in the murine left quadriceps femoris. Additionally, the results of the comparison were consistent with similar studies in higher-order animal models, suggesting that mouse models can be effectively employed to investigate the utility of DCS for various blood flow measurement applications.
Diffuse correlation tomography was utilized to noninvasively monitor 3D blood flow
changes in three types of healing mouse femoral grafts. Results reveal the spatial and temporal
difference among the groups.
Turgut Durduran, Chao Zhou, Erin Buckley, Meeri Kim, Guoqiang Yu, Regine Choe, J. William Gaynor, Thomas Spray, Suzanne Durning, Stefanie Mason, Lisa Montenegro, Susan Nicolson, Robert Zimmerman, Mary Putt, Jiongjiong Wang, Joel Greenberg, John Detre, Arjun Yodh, Daniel Licht
We employ a hybrid diffuse correlation spectroscopy (DCS) and near-infrared spectroscopy (NIRS) monitor for neonates with congenital heart disease (n=33). The NIRS-DCS device measured changes during hypercapnia of oxyhemoglobin, deoxyhemoglobin, and total hemoglobin concentrations; cerebral blood flow (rCBFDCS); and oxygen metabolism (rCMRO2). Concurrent measurements with arterial spin-labeled magnetic resonance imaging (rCBFASL-MRI, n=12) cross-validate rCBFDCS against rCBFASL-MRI, showing good agreement (R=0.7, p=0.01). The study demonstrates use of NIRS-DCS on a critically ill neonatal population, and the results indicate that the optical technology is a promising clinical method for monitoring this population.
We have developed a novel parallel-plate diffuse optical tomography (DOT) system for three-dimensional in vivo imaging of human breast tumor based on large optical data sets. Images of oxy-, deoxy-, and total hemoglobin concentration as well as blood oxygen saturation and tissue scattering were reconstructed. Tumor margins were derived using the optical data with guidance from radiology reports and magnetic resonance imaging. Tumor-to-normal ratios of these endogenous physiological parameters and an optical index were computed for 51 biopsy-proven lesions from 47 subjects. Malignant cancers (N=41) showed statistically significant higher total hemoglobin, oxy-hemoglobin concentration, and scattering compared to normal tissue. Furthermore, malignant lesions exhibited a twofold average increase in optical index. The influence of core biopsy on DOT results was also explored; the difference between the malignant group measured before core biopsy and the group measured more than 1 week after core biopsy was not significant. Benign tumors (N=10) did not exhibit statistical significance in the tumor-to-normal ratios of any parameter. Optical index and tumor-to-normal ratios of total hemoglobin, oxy-hemoglobin concentration, and scattering exhibited high area under the receiver operating characteristic curve values from 0.90 to 0.99, suggesting good discriminatory power. The data demonstrate that benign and malignant lesions can be distinguished by quantitative three-dimensional DOT.
We combine diffuse optical spectroscopy (DOS) and diffuse correlation spectroscopy (DCS) to noninvasively monitor early hemodynamic response to neoadjuvant chemotherapy in a breast cancer patient. The potential for early treatment monitoring is demonstrated. Within the first week of treatment (day 7) DOS revealed significant changes in tumor/normal contrast compared to pretreatment (day 0) tissue concentrations of deoxyhemoglobin (rctHHbT/N=69±21%), oxyhemoglobin (rctO2HbT/N=73±25%), total hemoglobin (rctTHbT/N=72±17%), and lipid concentration (rctLipidT/N=116±13%). Similarly, DCS found significant changes in tumor/normal blood flow contrast (rBFT/N=75±7% on day 7 with respect to day 0). Our observations suggest the combination of DCS and DOS enhances treatment monitoring compared to either technique alone. The hybrid approach also enables construction of indices reflecting tissue metabolic rate of oxygen, which may provide new insights about therapy mechanisms.
We present a novel methodology for combining breast image data obtained at different times, in different geometries, and by different techniques. We combine data based on diffuse optical tomography (DOT) and magnetic resonance imaging (MRI). The software platform integrates advanced multimodal registration and segmentation algorithms, requires minimal user experience, and employs computationally efficient techniques. The resulting superposed 3-D tomographs facilitate tissue analyses based on structural and functional data derived from both modalities, and readily permit enhancement of DOT data reconstruction using MRI-derived a-priori structural information. We demonstrate the multimodal registration method using a simulated phantom, and we present initial patient studies that confirm that tumorous regions in a patient breast found by both imaging modalities exhibit significantly higher total hemoglobin concentration (THC) than surrounding normal tissues. The average THC in the tumorous regions is one to three standard deviations larger than the overall breast average THC for all patients.
In this paper, we describe a novel clinical breast diffuse optical tomography (DOT) instrument for CW and RF data acquisition in transmission geometry. It is designed to be able to acquire a massive amount of data in a short amount of time available for patient measurement by using a 209-channel galvo-based fast optical switch
and a fast electron-multiplying CCD. In addition to CW measurements, RF measurements were made by using an electro-optic modulator for source modulation and a gain-modulated image intensifier for detection. The patient bed has many clinically-oriented features as well as improved data acquisition rate and transmission RF
measurement capability. A series of preliminary results will be shown, including a heterodyne RF experiment
for bulk property measurement and a CW experiment for 3D imaging. In order to deal with large data size, a
linear reconstruction algorithm that exploits separability of the inverse problem in Fourier domain is used for
fast and memory-load-free reconstruction.
We have developed a novel method for combining non-concurrent MR and DOT data, which integrates advanced
multimodal registration and segmentation algorithms within a well-defined workflow. The method requires little user
interaction, is computationally efficient for practical applications, and enables joint MR/DOT analysis. The method
presents additional advantages: More flexibility than integrated MR/DOT imaging systems, The ability to independently
develop a standalone DOT system without the stringent limitations imposed by the MRI device environment, Enhancement
of sensitivity and specificity for breast tumor detection, Combined analysis of structural and functional data,
Enhancement of DOT data reconstruction through the use of MR-derived a priori structural information. We have
conducted an initial patient study which asks an important question: how can functional information on a tumor
obtained from DOT data be combined with the anatomy of that tumor derived from MRI data? The study confirms that
tumor areas in the patient breasts exhibit significantly higher total hemoglobin concentration (THC) than their
surroundings. The results show significance in intra-patient THC variations, and justify the use of our normalized
difference measure defined as the distance from the average THC inside the breast, to the average THC inside the tumor
volume in terms of the THC standard deviation inside the breast. This method contributes to the long-term goal of
enabling standardized direct comparison of MRI and DOT and facilitating validation of DOT imaging methods in
clinical studies.
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.
We have developed a software platform for multimodal integration and visualization of diffuse optical tomography and magnetic resonance imaging. Novel registration and segmentation algorithms have been integrated into the platform. The multimodal registration technique enables the alignment of non-concurrently acquired MR and DOT breast data. The non-rigid registration algorithm uses two-dimensional signatures (2D digitally reconstructed radiographs) of the reference and moving volumes in order to register them. Multiple two-dimensional signatures can robustly represent the volume depending on the way signatures are generated. An easy way to conceptualize the idea is to understand the motion of an object by tracking three perpendicular shadows of the object. The breast MR image segmentation
technique enables a priori structural information derived from MRI to be incorporated into the reconstruction of DOT data. The segmentation algorithm is based on "Random walkers". Both registration and segmentation algorithms were tested and have shown promising results. The average Target Registration Error (TRE) for phantom models simulating the large breast compression differences was always below 5%. Tests on patient datasets also showed satisfying visual results. Several tests were also conducted for segmentation assessment and results have shown high quality MR breast image segmentation.
We have developed a software platform for multimodal integration and visualization of diffuse optical tomography (DOT) and magnetic resonance imaging (MRI) of breast cancer. The image visualization platform allows multimodality 3D image visualization and manipulation of datasets, such as a variety of 3D rendering technique, and the ability to simultaneously control multiple fields of view. This platform enables quantitative and qualitative analysis of structural and functional diagnostic data, using both conventional & molecular imaging. The functional parameters, together with morphological parameters from MR can be suitably combined and correlated to the absolute diagnosis from histopathology. Fusion of the multimodal datasets will eventually lead to a significant improvement in the sensitivity and specificity of breast cancer detection. Fusion may also allow a priori structural information derived from MRI to be incorporated into the reconstruction of diffuse optical tomography images. We will present the early results of image visualization and registration on multimodal breast cancer data, DOT and MRI.
A study using pregnant sheep was designed to simulate fetal hypoxia in order to investigate the ability of near-infrared spectroscopy (NIRS) to detect and quantify fetal hypoxia in utero. The near-infrared spectroscopic probe consisted of two detectors and six source positions. It was placed on the maternal ewe abdomen above the fetal head. The light sources were modulated at 70 MHz and frequency-encoded so that simultaneous measurements at 675, 786, 830 nm for each source position were possible. After the baseline measurements, fetal hypoxia was induced by blocking the aorta of pregnant ewe and thus compromising the blood supply to the uterus. Blood gas samples were concurrently drawn from the fetal brachial artery and jugular veins. Analysis of the diffuse optical data used a two-layer model to separate the maternal layer from the fetal head. The analysis also employed a priori spectral information about tissue chromophores. This approach provided good quantification of blood oxygenation changes, which correlated well with the blood gas analyses. By contrast the homogeneous model underestimated oxygenation changes during hypoxia.
This paper describes the design, development and characterization of dual wavelength, phase modulated device in near IR region which can be used for real time monitoring of oxy- and deoxy-hemoglobin. The device measures amplitude and phase which can be employed in the diffusion equation for a homogeneous semi-infinite medium to obtain the concentration of oxy- and deoxy-hemoglobin of the sample.
We present a preliminary assessment of the feasibility of using a frequency domain spectrometer for measuring fetal cerebral blood oxygenation in-utero at 750 and 780 nm of modulation at 70 MHz. The amplitude and phase of the diffuse photon density wave which propagates through the tissue is detected by a photomultiplier tube. The absorption coefficient ?a and the reduced scattering coefficient ?'s are calculated based on the analytic solution of the photon diffusion equation for a semi-infinite geometry. The accuracy of the instrument and the algorithm in measuring ?a is tested by an experiment performed on a homogeneous ink/intralipid tissue phantom. Also the sensitivity of the system to the change of blood volume and oxgenation is evaluated through a homogeneous blood/intralipid tissue phantom experiment. Clinical data was recorded during the elective Cesarean section of human subjects. The measurements were made on maternal abdomen in the post-epidural stage and on the fontanel region of neonate before (pre-cord) and after (post-cord) the umbilical cord was detached. The source detector separation used were 7 and 3(or 4) cm respectively. The deoxygenated and oxygenated hemoglobin concentration, blood volume and saturation were calculated based on ?a of 2 wavelength. The averaged optical properties and blood parameters for each stage are presented. The post-epidural blood saturation value correlates well with the pre-cord saturation value. A larger number of human subjects are being evaluated to provide statistically significant results.
Pulse oximetry (oxygen saturation monitoring) has markedly improved medical care in many fields, including anesthesiology, intensive care, and newborn intensive care. In obstetrics, fetal heart rate monitoring remains the standard for intrapartum assessment of fetal well being. Fetal oxygen saturation monitoring is a new technique currently under development. It is potentially superior to electronic fetal heart rate monitoring (cardiotocography) because it allows direct assessment of both fetal oxygen status and fetal tissue perfusion. Here, we present feasibility studies for trans-abdominal fetal cerebral pulse oximetry. Our experiments on more than 20 patients indicate feasibility. We will present the methodology for obtaining these data, as well as a summary of our pilot clinical study.
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