The ability to monitor disease progression over time is critical to inform patient care and prognosis, especially in usual interstitial pneumonia (UIP), the histopathological pattern seen in idiopathic pulmonary fibrosis (IPF). HRCT is limited in resolution to detect disease changes on a microscopic level, and surgical lung biopsy (SLB) has high risk of morbidity and mortality precluding its use to assess progression. Endobronchial optical coherence tomography (EB-OCT) is a bronchoscopic, minimally-invasive, high-resolution imaging method that accurately detects microscopic ILD features and is repeatable. Here, we evaluate the utility of repeat EB-OCT for monitoring microscopic disease progression in UIP/IPF.
Deep venous thrombosis is a global health problem with significant complications and high recurrence. Supporting the search for more effective therapies, polarization-sensitive optical coherence tomography (PS-OCT) may offer diagnostic imaging to determine the age of thrombus and personalize treatment. To assess sensitivity to thrombus aging, the IVC of two rat cohorts were imaged in-vivo at 24 hours (acute) or 28 days (chronic) after thrombus creation. The PS-OCT metrics were capable of differentiating acute and chronic thrombi with 98.2% total accuracy. These results demonstrate that PS-OCT is sensitive to structural changes in thrombi and could help guide advanced thrombolytic therapies.
Idiopathic pulmonary fibrosis (IPF) is a fatal form of interstitial lung disease (ILD), characterized by abnormal collagen deposition. Computed tomography imaging lacks the resolution to accurately distinguish and quantify fibrosis distribution at the microscopic level, and surgical biopsy methods are invasive. We demonstrate the feasibility of polarization sensitive endobronchial optical coherence tomography (PS EB-OCT) for quantitative in vivo microscopic assessment of fibrotic ILDs. PS EB-OCT was able to accurately distinguish fibrosis distribution patterns in IPF and non-IPF ILDs, independently compared against surgical biopsy. These findings support the potential of PS EB-OCT as a minimally-invasive method for assessment of ILD.
Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal type of interstitial lung disease (ILD) characterized by abnormal fibrotic scarring of lung parenchyma. We have demonstrated the use of endobronchial optical coherence tomography (EB-OCT) as a minimally-invasive approach for in vivo diagnosis of ILD in patients with high sensitivity and specificity. Here, we investigate the feasibility of EB-OCT elastography to measure the microscopic mechanical properties of normal and fibrotic lung parenchymal tissue in ex vivo porcine lung and in vivo in human subjects with ILD.
Idiopathic pulmonary fibrosis (IPF) is a fatal form of fibrotic interstitial lung disease (ILD). Early diagnosis of IPF is essential, however, resolution limitations of HRCT prohibit identification and monitoring of early microanatomic alterations. Developing precise imaging biomarkers using quantitative imaging features and artificial intelligence has significant potential for early diagnosis of IPF and non IPF ILDs, as well as for monitoring disease progression and therapeutic response. We demonstrate the feasibility of a deep learning-based algorithm for accurate segmentation and classification of salient microscopic ILD imaging features on endobronchial optical coherence tomography (EB-OCT) imaging.
Early, accurate diagnosis of interstitial lung disease (ILD) is critical for clinical management and therapeutic decision-making, especially distinguishing idiopathic pulmonary fibrosis (IPF) from non-IPF ILD. Unfortunately, current diagnostic imaging methods are limited in resolution and surgical biopsy methods are invasive. In this study, we evaluate the accuracy of endobronchial optical coherence tomography (EB-OCT) as a low-risk method for in vivo ILD diagnosis in patients undergoing surgical biopsy. EB-OCT was able to distinguish diagnostic microanatomical features of IPF from non-IPF ILDs, independently compared against surgical biopsy. These findings support the potential of OCT as a minimally-invasive method for IPF diagnosis.
Idiopathic pulmonary fibrosis (IPF) is a fatal form of fibrotic interstitial lung disease (ILD). Early diagnosis of IPF is essential, but often requires invasive surgery. We conduct a prospective study evaluating the diagnostic accuracy of endobronchial optical coherence tomography (EB-OCT) for IPF diagnosis as compared to concurrent surgical lung biopsy (SLB) and clinical follow-up diagnosis. EB-OCT was performed immediately prior to SLB in 27 ILD patients. EB-OCT was 100% sensitive and 100% specific for both histologic and clinical follow up diagnosis of IPF. The results demonstrate the potential of EB-OCT as minimally-invasive, low-risk in vivo method for microscopic IPF diagnosis.
Inadequacy of tumor tissue in transthoracic core needle biopsy (CNB) and transbronchial biopsy specimens, often due to contamination by fibrosis and normal lung elements, precludes accurate diagnosis, tumor subtyping and molecular testing, and impedes biobanking for research. Frozen section and touch prep methods are not utilized for adequacy assessment because they are destructive and consume tissue. We investigate polarization sensitive optical coherence tomography (PS-OCT), including birefringence and degree of depolarization uniformity metrics, for non-destructive, volumetric quantification of tumor yield in lung CNB specimens. PS-OCT distinguishes tumor, fibrosis and lung parenchyma with high accuracy, demonstrating potential for rapid CNB adequacy assessment.
Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive form of interstitial lung disease (ILD). High-resolution CT (HRCT) is currently used to identify macroscopic IPF features. However, for 50% of patients, ultimate diagnosis relies on microscopic features from invasive, high-risk surgical biopsies (SLBX). We conducted a pilot study to assess endobronchial OCT (EB-OCT) for in vivo diagnosis of IPF, enrolling ILD patients with nondiagnostic HRCT undergoing SLBX. EB-OCT visualized salient IPF features, including microscopic features not visible on HRCT, and accurately diagnosed IPF and non-IPF ILD as compared with SLBX. EB-OCT has the potential for in vivo microscopic diagnosis of IPF.
The goal of bronchial thermoplasty (BT) is to reduce the symptoms associated with asthma by ablating the hyper-responsive airway smooth (ASM), but results have been mixed. In this work we present the results of a study in which we imaged canines before and after BT using polarization-sensitive optical coherence tomography (PS-OCT) in order to assess the potential of PS-OCT for use in conjunction with the BT procedure. By employing a novel processing technique we demonstrate PS-OCT results obtained at full system resolution, allowing us to accurately measure even vanishingly thin ASM distributions following the BT procedure.
Diagnosis of peripheral lung nodules through transbronchial biopsy is highly prone to sampling errors due to the inability of current techniques to accurately locate and/or sample lesions. Volumetric optical imaging techniques such as optical coherence tomography (OCT) have the potential to address this issue, however, current imaging catheter designs cannot achieve sufficiently high-resolution, or diffraction-limited imaging; focusing elements bear spherical aberrations and multilayered structures with asymmetric curvatures in the optical path cause astigmatism. In this work, we propose a new class of optical imaging catheters – termed nano-optic endoscope – that use metalenses to achieve diffraction-limited endoscopic imaging at greatly extended depth-of-focus through negating non-chromatic aberrations and chromatic dispersion engineering. A metalens consists of a 2-dimentional array of subwavelength-spaced scatterers with specific geometric parameters and distribution that locally shift the phase of the incident light and modify its wavefront. The metalens ability to arbitrarily and accurately modify the phase allows the nano-optic endoscope to overcome spherical aberrations and astigmatism. Remarkably, the tailored chromatic dispersion of the metalens in the context of spectral interferometry is utilized to maintain high-resolution imaging beyond the input field Rayleigh range, overcoming the compromise between transverse resolution and depth-of-focus. Endoscopic imaging is demonstrated ex vivo in resected human airway specimens and in vivo in sheep airways. Fine pathology such as irregular glandular pattern, the hallmark of adenocarcinoma, is readily visualized in high-resolution images captured by the nano-optic endoscope. The versatility and design flexibility of the nano-optic endoscope significantly elevate endoscopic imaging capabilities that will likely impact clinical applications.
Acquisition of high-resolution images from within internal organs using endoscopic optical imaging has several clinical applications. In particular, endoscopic optical coherence tomography (OCT) capable of visualizing tissue microstructures is emerging as a promising tool for detection, diagnosis, and monitoring of disease in luminal organs. However, difficulties associated with optical aberrations and the trade-off between transverse resolution and depth-of-focus significantly limits the scope of applications. This work presents a new class of optical imaging catheters termed nano-optic endoscopes that address the difficulties associated with current endoscopic imaging catheters. We incorporate a metalens with the ability to modify the phase of incident light at sub-wavelength level into the design of an OCT catheter to achieve near diffraction-limited imaging through negating non-chromatic aberrations. A metalens consists of a 2-dimentional array of subwavelength-spaced scatterers with specific geometric parameters and distribution that locally shift the phase of the incident light and modify its wavefront. The metalens ability to arbitrarily and accurately modify the phase allows the nano-optic endoscope to overcome spherical aberrations and astigmatism, the essential barriers to diffraction-limited imaging. Remarkably, the tailored chromatic dispersion of the metalens in the context of spectral interferometry is utilized to maintain high-resolution imaging beyond the input field Rayleigh range, overcoming the compromise between transverse resolution and depth-of-focus. Endoscopic imaging is demonstrated in resected human and swine airway specimens and in sheep airways in vivo. The versatility and design flexibility of the nano-optic endoscope significantly elevate endoscopic imaging capabilities that will likely impact clinical applications.
To better understand bronchoconstriction in asthma, it is critical to dynamically visualize airway behavior in vivo. However, currently available imaging techniques do not have sufficient temporal and spatial resolution to investigate airway dynamics. We propose to use endobronchial Optical Coherence Tomography (OCT) to provide real-time cross-sectional images of airway dynamics with a high spatial resolution. Our aim was to study the structure and function of spatially distinct airways during tidal breathing (TB), breath-holds (BH) at end inspiration, and in a response to single deep inspiration (DI) and multiple DI (MDI) in a preclinical sheep asthma model.
Anesthetized and mechanically ventilated sheep (n=3) were imaged with OCT in 4 dependent and 4 non-dependent airways at baseline and in methacholine constricted airways. We assessed airway morphology during TB, BH, DI and MDI maneuvers.
The change in airway lumen area was found to be greater in the dependent airways compared to the non-dependent airways during TB (dependent: +14.9%, non-dependent: +6%) at baseline. Similarly, the dependent airways dilated more than the non-dependent airways in response to BH (dependent: +7.9%, non-dependent: +5.7%) in relaxed condition. Conversely, in the constricted lung, the DI and MDI maneuvers dilated the non-dependent airways (+13.6% DI, +44% MDI) more than the dependent airways (+6% DI, +15.5% MDI). Overall, dependent airways were more distensible than non-dependent airways during TB and BH, while this behavior was reversed following DI and MDI maneuvers in constricted airways possibly due to a greater local methacholine delivery due to gravitational dependencies on perfusion.
Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal form of fibrotic lung disease, with a significantly worse prognosis than other forms of pulmonary fibrosis (3-year survival rate of 50%). Distinguishing IPF from other fibrotic diseases is essential to patient care because it stratifies prognosis and therapeutic decision-making. However, making the diagnosis often requires invasive, high-risk surgical procedures to look for microscopic features not seen on chest CT, such as characteristic cystic honeycombing in the peripheral lung. Optical coherence tomography (OCT) provides rapid 3D visualization of large tissue volumes with microscopic resolutions well beyond the capabilities of CT. We aim to determine whether bronchoscopic OCT can provide a low-risk, non-surgical method for IPF diagnosis. We have developed bronchoscopic OCT catheters that access the peripheral lung and conducted in vivo peripheral lung imaging in patients, including those with pulmonary fibrosis. We also conducted bronchoscopic OCT in ex vivo lung from pulmonary fibrosis patients, including IPF, to determine if OCT could successfully visualize features of IPF through the peripheral airways. Our results demonstrate that OCT is able to visualize characteristic features of IPF through the airway, including microscopic honeycombing (< 1 mm diameter) not visible by CT, dense peripheral fibrosis, and spatial disease heterogeneity. We also found that OCT has potential to distinguish mimickers of IPF honeycombing, such as traction bronchiectasis and emphysema, from true honeycombing. These findings support the potential of bronchoscopic OCT as a minimally-invasive method for in vivo IPF diagnosis. However, future clinical studies are needed to validate these findings.
The ability to observe airway dynamics is fundamental to forming a complete understanding of pulmonary diseases such as asthma. We have previously demonstrated that Optical Coherence Tomography (OCT) can be used to observe structural changes in the airway during bronchoconstriction, but standard OCT lacks the contrast to discriminate airway smooth muscle (ASM) bands- ASM being responsible for generating the force that drives airway constriction- from the surrounding tissue. Since ASM in general exhibits a greater degree of birefringence than the surrounding tissue, a potential solution to this problem lies in the implementation of polarization sensitivity (PS) to the OCT system. By modifying the OCT system so that it is sensitive to the birefringence of tissue under inspection, we can visualize the ASM with much greater clarity and definition. In this presentation we show that the force of contraction can be indirectly measured by an associated increase in the birefringence signal of the ASM. We validate this approach by attaching segments of swine trachea to an isometric force transducer and stimulating contraction, while simultaneously measuring the exerted force and imaging the segment with PS-OCT. We then show how our results may be used to extrapolate the force of contraction of closed airways in absence of additional measurement devices. We apply this technique to assess ASM contractility volumetrically and in vivo, in both asthmatic and non-asthmatic human volunteers.
Tissue biopsy is the principal method used to diagnose tumors in a variety of organ systems. It is essential to maximize tumor yield in biopsy specimens for both clinical diagnostic and research purposes. This is particularly important in tumors where additional tissue is needed for molecular analysis to identify patients who would benefit from mutation-specific targeted therapy, such as in lung carcinomas. Inadvertent sampling of fibrotic stroma within tumor nodules contaminates biopsies, decreases tumor yield, and can impede diagnosis. The ability to assess tumor composition and guide biopsy site selection in real time is likely to improve diagnostic yield. Polarization sensitive OCT (PS-OCT) measures birefringence in organized tissues, such as collagen, and could be used to distinguish tumor from fibrosis. In this study, PS-OCT was obtained in 65 lung nodule samples from surgical resection specimens containing varying ratios of tumor and fibrosis. PS-OCT was obtained with either a custom-built helical scanning catheter (0.8 or 1.6mm in diameter) or a dual-axis bench top scanner. Strong birefringence was observed in nodules containing dense fibrosis, with no birefringence in adjacent regions of tumor. Tumors admixed with early, loosely-organized collagen demonstrated mild-to-moderate birefringence, and tumors with little collagen content showed little to no birefringent signal. PS-OCT provides significant insights into tumor nodule composition, and has potential to differentiate tumor from stromal fibrosis during biopsy site selection to increase diagnostic tumor yield.
Despite significant advances in targeted therapies for lung cancer, nearly all patients develop drug resistance within 6-12 months and prognosis remains poor. Developing drug resistance is a progressive process that involves tumor cells and their microenvironment. We hypothesize that microenvironment factors alter tumor growth and response to targeted therapy. We conducted in vitro studies in human EGFR-mutant lung carcinoma cells, and demonstrated that factors secreted from lung fibroblasts results in increased tumor cell survival during targeted therapy with EGFR inhibitor, gefitinib. We also demonstrated that increased environment stiffness results in increased tumor survival during gefitinib therapy. In order to test our hypothesis in vivo, we developed a multimodal optical imaging protocol for preclinical intravital imaging in mouse models to assess tumor and its microenvironment over time. We have successfully conducted multimodal imaging of dorsal skinfold chamber (DSC) window mice implanted with GFP-labeled human EGFR mutant lung carcinoma cells and visualized changes in tumor development and microenvironment facets over time. Multimodal imaging included structural OCT to assess tumor viability and necrosis, polarization-sensitive OCT to measure tissue birefringence for collagen/fibroblast detection, and Doppler OCT to assess tumor vasculature. Confocal imaging was also performed for high-resolution visualization of EGFR-mutant lung cancer cells labeled with GFP, and was coregistered with OCT. Our results demonstrated that stromal support and vascular growth are essential to tumor progression. Multimodal imaging is a useful tool to assess tumor and its microenvironment over time.
David Adams, Alyssa Miller, Jasmin Holz, Margit Szabari, Lida Hariri, R. Scott Harris, Jocelyn Cho, Daniel Hamilos, Andrew Luster, Benjamin Medoff, Melissa Suter
Asthma affects hundreds of millions of people worldwide, and the prevalence of the disease appears to be increasing. One of the most important aspects of asthma is the excessive bronchoconstriction that results in many of the symptoms experienced by asthma sufferers, but the relationship between bronchoconstriction and airway morphology is not clearly established. We present the imaging results of a study involving a segmental allergen challenge given to both allergic asthmatic (n = 12) and allergic non-asthmatic (n = 19) human volunteers. Using OCT, we have imaged and assessed baseline morphology in a right upper lobe (RUL) airway, serving as the control, and a right middle lobe (RML) airway, in which the allergen was to be administered. After a period of 24 hours had elapsed following the administration of the allergen, both airways were again imaged and the response morphology assessed. A number of airway parameters were measured and compared, including epithelial thickness, mucosal thickness and buckling, lumen area, and mucus content. We found that at baseline epithelial thickness, mucosal thickness, and mucosal buckling were greater in AAs than ANAs. We also observed statistically significant increases in these values 24 hours after the allergen had been administered for both the ANA and AA sets. In comparison, the control airway which received a diluent showed no statistically significant change.
Although mechanical ventilation (MV) is necessary to support gas exchange in critically ill patients, it can contribute to the development of lung injury and multiple organ dysfunction. It is known that high tidal volume (Vt) MV can cause ventilator-induced lung injury (VILI) in healthy lungs and increase the mortality of patients with Acute Respiratory Distress Syndrome. Low level laser therapy (LLLT) has demonstrated to have anti-inflammatory effects. We investigated whether LLLT could alleviate inflammation from injurious MV in mice.
Adult mice were assigned to 2 groups: VILI+LLLT group (3 h of injurious MV: Vt=25-30 ml/kg, respiratory rate (RR)=50/min, positive end-expiratory pressure (PEEP)=0 cmH20, followed by 3 h of protective MV: Vt=9 ml/kg, RR=140/min, PEEP=2 cmH20) and VILI+no LLLT group. LLLT was applied during the first 30 min of the MV (810 nm LED system, 5 J/cm2, 1 cm above the chest). Respiratory impedance was measured in vivo with forced oscillation technique and lung mechanics were calculated by fitting the constant phase model. At the end of the MV, bronchoalveolar lavage (BAL) was performed and inflammatory cells counted. Lungs were removed en-bloc and fixed for histological evaluation.
We hypothesize that LLLT can reduce lung injury and inflammation from VILI. This therapy could be translated into clinical practice, where it can potentially improve outcomes in patients requiring mechanical ventilation in the operating room or in the intensive care units.
Present understanding of the pathophysiological mechanisms of asthma has been severely limited by the lack of an imaging modality capable of assessing airway conditions of asthma patients in vivo. Of particular interest is the role that airway smooth muscle (ASM) plays in the development of asthma and asthma related symptoms. With standard Optical Coherence Tomography (OCT), imaging ASM is often not possible due to poor structural contrast between the muscle and surrounding tissues. A potential solution to this problem is to utilize additional optical contrast factors intrinsic to the tissue, such as birefringence. Due to its highly ordered structure, ASM is strongly birefringent. Previously, we demonstrated that Polarization Sensitive OCT(PS-OCT) has the potential to be used to visualize ASM as well as easily segment it from the surrounding (weakly) birefringent tissue by exploiting a property which allows it to discriminate the orientation of birefringent fibers. We have already validated our technology with a substantial set of histological comparisons made against data obtained ex vivo. In this work we present a comprehensive comparison of ASM distributions in asthmatic and non-asthmatic human volunteers. By isolating the ASM we parameterize its distribution in terms of both thickness and band width, calculated volumetrically over centimeters of airway. Using this data we perform analyses of the asthmatic and non-asthmatic airways using a broad number and variety and subjects.
Asthma is a chronic disease resulting in periodic attacks of coughing and wheezing due to temporarily constricted and clogged airways. The pathophysiology of asthma and the process of airway narrowing are not completely understood. Appropriate in vivo imaging modality with sufficient spatial and temporal resolution to dynamically assess the behavior of airways is missing. Optical coherence tomography (OCT) enables real-time evaluation of the airways during dynamic and static breathing maneuvers. Our aim was to visualize the structure and function of airways in healthy and Methacholine (MCh) challenged lung.
Sheep (n=3) were anesthetized, mechanically ventilated and imaged with OCT in 4 dependent and 4 independent airways both pre- and post-MCh administration. The OCT system employed a 2.4 Fr (0.8 mm diameter) catheter and acquired circumferential cross-sectional images in excess of 100 frames per second during dynamic tidal breathing, 20 second static breath-holds at end-inspiration and expiration pressure, and in a response to a single deep inhalation.
Markedly different airway behavior was found in dependent versus non-dependent airway segments before and after MCh injection. OCT is a non-ionizing light-based imaging modality, which may provide valuable insight into the complex dynamic behavior of airway structure and function in the normal and asthmatic lung.
Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal form of fibrotic lung disease, with a 3 year survival rate of 50%. Diagnostic certainty of IPF is essential to determine the most effective therapy for patients, but often requires surgery to resect lung tissue and look for microscopic honeycombing not seen on chest computed tomography (CT). Unfortunately, surgical lung resection has high risks of associated morbidity and mortality in this patient population. We aim to determine whether bronchoscopic optical coherence tomography (OCT) can serve as a novel, low-risk paradigm for in vivo IPF diagnosis without surgery or tissue removal. OCT provides rapid 3D visualization of large tissue volumes with microscopic resolutions well beyond the capabilities of CT. We have designed bronchoscopic OCT catheters to effectively and safely access the peripheral lung, and conducted in vivo peripheral lung imaging in patients, including those with pulmonary fibrosis. We utilized these OCT catheters to perform bronchoscopic imaging in lung tissue from patients with pulmonary fibrosis to determine if bronchoscopic OCT could successfully visualize features of IPF through the peripheral airways. OCT was able to visualize characteristic features of IPF through the airway, including microscopic honeycombing (< 1 mm diameter) not visible by CT, dense peripheral fibrosis, and spatial disease heterogeneity. These findings support the potential of bronchoscopic OCT as a minimally-invasive method for in vivo IPF diagnosis. However, future clinical studies are needed to validate these findings.
KEYWORDS: In vivo imaging, Optical coherence tomography, Polarization, Birefringence, Photomedicine, Coherence (optics), Biomedical optics, Current controlled current source
Present understanding of the pathophysiological mechanisms of asthma has been severely limited by the lack of an imaging modality capable of assessing airway conditions of asthma patients in vivo. Of particular interest is the role that airway smooth muscle (ASM) plays in the development of asthma and asthma related symptoms. We have developed novel techniques that we applied to Polarization Sensitive OCT (PS-OCT) in order to assess ASM, and validated our results with a substantial number of histological matches. In this work we employ our system in the study of ASM distributions in both asthmatic and non-asthmatic airways with data obtained in vivo from human volunteers. By isolating the ASM and performing volumetric analysis we obtain a variety of informative metrics such as ASM thickness and band width, and compare these quantities between subject types. Furthermore, we demonstrate that the degree of birefringence of the ASM can be associated with contractility, allowing us to estimate pressure exerted by ASM during contraction. We apply this technique to in vivo datasets from human volunteers as well.
Lung cancer is the leading cause of cancer related death. Macroscopic imaging techniques such as computed tomography are highly sensitivity at detecting small, ≤ 2cm, peripheral pulmonary lesions (PPLs) in the lung but lack the specificity necessary for diagnosis. Bronchoscopy is a procedure routinely performed to diagnose PPLs but is hindered with a low diagnostic yield due to challenging lesion localization. We have developed a flexible transbronchial optical frequency domain imaging (TB-OFDI) catheter that functions as a ‘smart needle’ to confirm the needle placement within the target lesion prior to biopsy. The TB-OFDI smart needle consists of a flexible and removable OFDI catheter that operates within a 21-gauge transbronchial needle aspiration (TBNA) needle. The OFDI catheter can be easily removed from the needle to facilitate subsequent aspiration or biopsy acquisition. The OFDI imaging core consists of an angled-polished ball lens with a spot size of 25 μm at a working distance of 160 μm from the catheter sheath. The ball-lens was designed to have an ellipsoid shape in order to compensate for the astigmatism caused by encasing the optics within a protective sheath. Transbronchial imaging of inflated excised swine lung parenchyma with the TB-OFDI smart needle yielded clear images of alveoli. In-vivo transbronchial imaging was also performed on three swine with artificial lesions injected transthoracially. Our results suggest that the TB-OFDI smart needle may be a useful tool for guiding biopsy acquisition to increase the diagnostic yield of PPLs.
Smoke inhalation injury is a serious threat to victims of fires and explosions, however accurate diagnosis of
patients remains problematic. Current evaluation techniques are highly subjective, often involving the integration
of clinical findings with bronchoscopic assessment. It is apparent that new quantitative methods for evaluating
the airways of patients at risk of inhalation injury are needed. Optical frequency domain imaging (OFDI) is a
high resolution optical imaging modality that enables volumetric microscopy of the trachea and upper airways in
vivo. We anticipate that OFDI may be a useful tool in accurately assessing the airways of patients at risk of smoke
inhalation injury by detecting injury prior to the onset of symptoms, and therefore guiding patient management.
To demonstrate the potential of OFDI for evaluating smoke inhalation injury, we conducted a preclinical study
in which we imaged the trachea/upper airways of 4 sheep prior to, and up to 60 minutes post exposure to
cooled cotton smoke. OFDI enabled the visualization of increased mucus accumulation, mucosal thickening,
epithelial disruption and sloughing, and increased submucosal signal intensity attributed to polymorphonuclear
infiltrates. These results were consistent with histopathology findings. Bronchoscopic inspection of the upper
airways appeared relatively normal with only mild accumulation of mucus visible within the airway lumen. The
ability of OFDI to not only accurately detect smoke inhalation injury, but to quantitatively assess and monitor
the progression or healing of the injury over time may provide new insights into the management of patients
such as guiding clinical decisions regarding the need for intubation and ventilator support.
Ovarian cancer is the fourth leading cause of cancer-related death among women. If diagnosed at early stages, 5-year survival rate is 94%, but drops to 68% for regional disease and 29% for distant metastasis; only 19% of cases are diagnosed at early, localized stages. Optical coherence tomography is a recently emerging non-destructive imaging technology, achieving high axial resolutions (10-20 µm) at imaging depths up to 2 mm. Previously, we studied OCT in normal and diseased human ovary ex vivo. Changes in collagen were suggested with several images that correlated with changes in collagen seen in malignancy. Areas of necrosis and blood vessels were also visualized using OCT, indicative of an underlying tissue abnormality. We recently developed a custom side-firing laparoscopic OCT (LOCT) probe fabricated for in vivo imaging. The LOCT probe, consisting of a 38 mm diameter handpiece terminated in a 280 mm long, 4.6 mm diameter tip for insertion into the laparoscopic trocar, is capable of obtaining up to 9.5 mm image lengths at 10 µm axial resolution. In this pilot study, we utilize the LOCT probe to image one or both ovaries of 17 patients undergoing laparotomy or transabdominal endoscopy and oophorectomy to determine if OCT is capable of differentiating normal and neoplastic ovary. We have laparoscopically imaged the ovaries of seventeen patients with no known complications. Initial data evaluation reveals qualitative distinguishability between the features of undiseased post-menopausal ovary and the cystic, non-homogenous appearance of neoplastic ovary such as serous cystadenoma and endometroid adenocarcinoma.
Optical coherence tomography, optical coherence microscopy, reflectance confocal microscopy, and darkfield
microscopy all derive contrast from the intensity of endogenous tissue scatter. We have imaged excised mouse colon
tissue with these complimentary technologies to make conclusions about structural origins of scatter in the mouse
colonic mucosa observed with endoscopic OCT. We find hyperintense scattering both from the cytoplasm of epithelial
cells and from the boundary between epithelia and the lamina propria. We find almost no scatter from the portion of
epithelial cells containing the nucleus. These observations substantiate explanations for the appearance of colonic crypts
and the luminal surface.
Ovarian cancer is the fourth leading cause of cancer-related death among women in the United States. If diagnosed at an
early stage, the 5-year survival rate is 94%, but drops to 68% for regional disease and 29% for distant metastasis; only
19% of all cases are diagnosed at the early, localized stage. Optical coherence tomography is a recently emerging non-destructive
imaging technology, achieving high axial resolutions (10-20 microns) at imaging depths up to 2 mm.
Previously, we studied OCT imaging in normal and diseased human ovary ex vivo to determine the features OCT is
capable of resolving. Changes in collagen were suggested with several of the images that correlated with changes in
collagen seen in malignancy. Areas of necrosis and blood vessels were also visualized using OCT, indicative of an
underlying tissue abnormality. We recently developed a custom side-firing laparoscopic OCT (LOCT) probe fabricated
specifically for in vivo laparoscopic imaging. The LOCT probe consists of a 38 mm diameter handpiece terminated in an
280 mm long, 4.6 mm diameter tip for insertion into the laparoscopic trocar and is capable of obtaining up to 9.5 mm
image lengths at 10 micron axial resolution. In this study, we utilize the LOCT probe to image one or both ovaries of 20
patients undergoing laparotomy or transabdominal endoscopy and oophorectomy to determine if OCT is capable of
identifying and/or differentiating normal and neoplastic ovary. To date, we have laparoscopically imaged the ovaries of
ten patients successfully with no known complications.
Purpose: Optical coherence tomography (OCT) is a minimally invasive, depth-resolved imaging tool that can be
commissioned for small diameter endoscopic applications for imaging mouse models of colorectal cancer. In this study,
we utilized ultrahigh resolution OCT (UHR OCT) to serially image the lower colon of azoxymethane (AOM) treated A/J
mouse models of CRC, monitor the progression of neoplastic transformations, and determine if OCT is capable of
identifying early disease.
Experimental Design: Thirteen AOM treated A/J and two control A/J mice were surveyed at four timepoints (8, 14, 22,
and 26 weeks post AOM treatment) using a prototype 2.0 mm diameter UHR OCT endoscope-based system that
achieved resolutions of 3.2 um axial and 4.4 um lateral. Histological samples were obtained at the final imaging
timepoint serving as the gold standard.
Results: Gross and histological assessment of the excised colonic tissue revealed at least one tumor in all 13 AOM
treated mice, with most mice developing multiple tumors. In the corresponding OCT images, a progression from healthy
thin mucosa to adenoma appearing as large, structurally disorganized masses was visualized over the imaging time
points correlating to the locations of the grossly visualized tumors.
Conclusions: This study indicates that UHR OCT enables accurate identification of disease and non-destructive
visualization of CRC progression in the lower colon of mice.
Endoscopic ultrahigh-resolution optical coherence tomography (OCT) enables collection of minimally invasive cross-sectional images in vivo, which may be used to facilitate rapid development of reliable mouse models of colon disease as well as assess chemopreventive and therapeutic agents. The small physical scale of mouse colon makes light penetration less problematic than in other tissues and high resolution acutely necessary. In our 2-mm diameter endoscopic time domain OCT system, isotropic ultrahigh-resolution is supported by a center wavelength of 800 nm and full-width-at-half-maximum bandwidth of 150 nm (mode-locked titanium:sapphire laser) combined with 1:1 conjugate imaging of a small core fiber. A pair of KZFSN5/SFPL53 doublets provides excellent color correction to support wide bandwidth throughout the imaging depth. A slight deviation from normal beam exit angle suppresses collection of the strong back reflection at the exit window surface. Our system achieves axial resolution of 3.2 µm in air and 4.4-µm lateral spot diameter with 101-dB sensitivity. Microscopic features too small to see in mouse tissue with conventional resolution systems, including colonic crypts, are clearly resolved. Resolution near the cellular level is potentially capable of identifying abnormal crypt formation and dysplastic cellular organization.
Optical Coherence Tomography (OCT) and Laser Induced Fluorescence Spectroscopy (LIF) have separately been found to have clinical potential in identifying human gastrointestinal (GI) pathologies, yet their diagnostic capability in mouse models of human disease is unknown. We combine the two modalities to survey the GI tract of a variety of mouse strains and sample dysplasias and inflammatory bowel disease (IBD) of the small and large intestine. Segments of duodenum and lower colon 2.5 cm in length and the entire esophagus from 10 mice each of two colon cancer models (ApcMin and AOM treated A/J) and two IBD models (Il-2 and Il-10) and 5 mice each of their respective controls were excised. OCT images and LIF spectra were obtained simultaneously from each tissue sample within 1 hour of extraction. Histology was used to classify tissue regions as normal, Peyer’s patch, dysplasia, adenoma, or IBD. Features in corresponding regions of OCT images were analyzed. Spectra from each of these categories were averaged and compared via the student's t-test. Features in OCT images correlated to histology in both normal and diseased tissue samples. In the diseased samples, OCT was able to identify early stages of mild colitis and dysplasia. In the sample of IBD, the LIF spectra displayed unique peaks at 635nm and 670nm, which were attributed to increased porphyrin production in the proliferating bacteria of the disease. These peaks have the potential to act as a diagnostic for IBD. OCT and LIF appear to be useful and complementary modalities for imaging mouse models.
Mouse models are increasingly important for studying human GI pathology. OCT provides minimally invasive, cross-sectional images that indicate the thickness and scattering density of underlying tissue. We have developed endoscopic ultrahigh resolution OCT (UHR-OCT) for the purpose of in vivo imaging in mouse colon. The reduced scale of the mouse colon makes tissue light penetration much less problematic, and high resolution acutely necessary. Higher lateral resolution requires a departure from the traditional cemented GRIN lens design. We support the need for better chromatic aberration than can be achieved by a GRIN lens using commercial raytracing software. We have designed and built a 2mm diameter endoscopic UHR-OCT system achromatized for 770-1020nm for use with a Titanium:sapphire laser with 260 nm bandwidth at full-width-half-maximum centered at 800 nm while achieving a 4.4um lateral spot dimension at focus. A pair of KZFSN5/SFPL53 doublets provides excellent primary and secondary color correction to maintain wide bandwidth through the imaging depth. A slight deviation from normal beam exit angle suppresses collection of the strong back reflection at the exit window surface. The novel design endoscope was built and characterized for through focus bandwidth, axial resolution, signal to noise, and lateral spot dimension. Performance is demonstrated on a variety of ex vivo tissues and in situ mouse colon. Ultrahigh-resolution images of mouse tissue enable the visualization of microscopic features, including crypts that have previously been observed with standard resolution OCT in humans but were too small to see in mouse tissue. Resolution near the cellular level is potentially capable of identifying abnormal crypt formation and dysplastic cellular organization.
Optical coherence tomography (OCT) is an imaging modality capable of acquiring cross-sectional images of tissue using back-reflected light. Conventional OCT images have a resolution of 10-15μm, and are thus best suited for visualizing tissue layers and structures. OCT images of collagen (with and without endothelial cells) have no resolvable features and may appear to simply show an exponential decrease in intensity with depth. However, examination of these images reveals that they display a characteristic repetitive structure due to speckle.
The purpose of this study is to evaluate the application of statistical and spectral texture analysis techniques for differentiating living and non-living tissue phantoms containing various sizes and distributions of scatterers based on speckle content in OCT images. Statistically significant differences between texture parameters and excellent classification rates were obtained when comparing various endothelial cell concentrations ranging from 0 cells/ml to 25 million/ml. Statistically significant results and excellent classification rates were also obtained using various sizes of microspheres with concentrations ranging from 0 microspheres/ml to 500 million microspheres/ml.
This study has shown that texture analysis of OCT images may be capable of differentiating tissue phantoms containing various sizes and distributions of scatterers.
An endoscopic system that provides simultaneous cross-sectional imaging and fluorescence spectroscopy is described. The first application of this device was the investigation of mouse colon cancer in vivo. This system combined optical coherence tomography (OCT), which provided high-resolution cross-sectional structural information in the form of a two-dimensional image, and laser induced fluorescence (LIF), which yielded histochemical information about the tissue. The design challenge and solution of packaging these two systems with widely different optical requirements are described in detail. The illumination geometry of the endoscope was similar to earlier published OCT and LIF catheter endoscope designs. However, several unique design challenges encountered in combining these two systems have been addressed. The use of a rodprism to reduce the asymmetry in the OCT beam caused by a cylindrical window is presented. Materials selection for use with wavelengths from 325nm - 1310nm presented a challenge usually avoided in OCT endoscopes. Preliminary mouse colon data collected with this endoscopic device is compared with previous experiments performed by researchers in our lab working with an earlier bulk-optic, combined OCT-LIF system.
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