We have developed a new self-propelled OCT imaging technology called retrograde Tethered Capsule Endomicroscopy
(R-TCE) for colonic disease screening. We successfully demonstrated that the R-TCE device can be advanced over 1 meter in 5 swine colons in vivo. R-TCE with balloon pullback imaging enabled full circumferential OCT visualization of 95.94 % ± 0.13% of the colon wall. 3D reconstructed colon OCT images and 3D rendered flythroughs showed that R-TCE is feasible for OCT microscopic imaging of the entire colon in vivo. When translated to humans, this R-TCE
technology may provide a less invasive and more efficient alternative to colonoscopy.
We developed OCT-TCE devices with either guidewire or propylene glycol infusion tethers and tested pullback force and tissue damage over different distances of the small intestine in living swine. For all devices, the maximum force was below our safety threshold of 2N across intestinal lengths of 4m or less. At lengths > 4m, the force was > 4N for the infusion tube devices and > 5N for the guidewire devices, and the proximal intestine showed visible damage matching the tether shape. In conclusion, TCE may be safe for jejunal imaging but likely needs further improvement for ileum imaging in humans.
Tethered capsule endomicroscopy (TCE) is a recently developed form of in vivo microscopy based on optical coherence tomography (OCT). With TCE, a small tethered pill is swallowed, procuring high resolution microscopic images of the esophageal wall. TCE does not require sedation and is thus a more rapid and convenient procedure comparing to traditional endoscopic examination. Our group and others have successfully conducted OCT-TCE in pilot, single-center studies that demonstrated the potential of this technology for upper GI tract diagnosis. Here, we demonstrate and evaluate the feasibility and safety of a next generation OCT-TCE system and device in patients with Barrett’s esophagus (BE) and report the initial longitudinal analysis of the natural history of BE.
A screening test for early detection of pancreatic cancer (PC) is a critical unmet need as PC is usually detected late when mortality is unavoidable. Pancreatic fluid (PF), excreted to the duodenum by the Ampulla of Vater (AoV), offers a promising sample for early stage pancreatic cancer screening as it is the richest source of PC bioanalytes. The successful identification of the AoV is critical to develop a minimally invasive and inexpensive capsule-based PC screening test. With our recently developed tether capsule endomicroscopy (TCE) technique, we imaged 27 subjects and analyzed 353 duodenal OCT-TCE datasets. Using relative positions of the major and minor ampulla, and influx of bile into the duodenum, we distinguished the major from the minor. At least one ampulla was identified in 100%, major ampulla identified in 85%, and minor ampulla identified in 67% of all subjects. The measured mean max. diameter of the major ampulla was 6.49 ± 2.23 mm, and 6.09 ± 2.05 mm for the minor.
The Tearney Lab at the Massachusetts General Hospital (MGH) has conducted a study using Tethered Capsule Endomicroscopy (TCE), a technique that involves swallowing a tethered capsule device that circumferentially scans an optical coherence technology (OCT) beam inside the body as it traverses the gastrointestinal tract. Throughout the procedure, microscopic images of the esophagus are acquired in real time in an unsedated subject. OCT TCE was used to screen for Barrett’s Esophagus in a setting of 2 primary care practices at MGH.The OCT TCE show promising results identifying BE in a primary care population.
KEYWORDS: Optical coherence tomography, Endomicroscopy, Intestine, Endoscopy, Inflammation, Biopsy, 3D image processing, Visualization, Control systems
Environmental Enteric Dysfunction (EED) is a poorly understood condition of the small intestine that is prevalent in regions of the world with inadequate sanitation and hygiene. EED affects 25% of all children globally and causes over a million deaths each year. The condition is associated with increased intestinal permeability, bacterial translocation, inflammation and villous blunting. The loss of absorptive area and intestinal function leads to nutrient malabsorption, with long term outcomes characterized by stunted growth and neurocognitive development. Currently, the only way to directly evaluate the morphology of the intestine is endoscopy with mucosal biopsy. Yet because EED is endemic in low and middle-income countries, endoscopy is untenable for studying EED. As a result, the diagnosis of EED and the assessment of the efficacy of EED interventions is hampered by an inability to evaluate the intestinal mucosa.
Our lab has previously developed a technology termed tethered capsule OCT endomicroscopy (TCE). The method involves swallowing an optomechanically-engineered pill that generates 3D images of the GI tract as it traverses the lumen of the organ via peristalsis, assisted by gravity. In order to study the potential of using TCE to investigate EED, we initiated and conducted a TCE study in adolescents at Aga Khan Medical Center in Pakistan. To make swallowing easier, the tethered capsule’s size was reduced from 11x25 mm to 8x22 mm. Villous morphologic visualization was enhanced by building a notch (x mm deep, y mm wide) in the capsule’s imaging window. To date, 26 Pakistani subjects with ages ranging from 14 to 18 y/o (16.4 +/- 1.0) have been enrolled and imaged. A total of 19 subjects were able to swallow the capsule. Of those, 9 successfully passed through the pylorus, allowing successful microscopic imaging of the entire duodenum. There were no adverse events in any of the cases. Maximum villous height and width were measured from 3 randomly chosen, representative frames from each Pakistan subject as well as a matching number from US controls. Preliminary results, comparing Pakistani vs US villous morphology, indicated that subjects from Pakistan have shorter (628.6 +/- 22.0 um and 492.3 +/- 13.2 um, respectively, p< 0.0001) and wider duodenal villi (244.9 +/- 8.8 um and 293.4 +/- 13.2 um, respectively, p< 0.0001). These findings suggest that OCT TCE of the duodenum may be a useful tool for evaluating villous morphology in EED.
While the most common method used to evaluate and survey patients with Barrett’s Esophagus (BE) is endoscopic biopsy, this procedure is invasive, time-consuming, and suffers from sampling errors. Moreover, it requires patient sedation that increases cost and mandates its operation in specialized settings. Our lab has developed a new imaging tool termed tethered capsule endomicroscopy (TCE) that involves swallowing a tethered capsule which utilizes optical coherence tomography (OCT) to obtain three-dimensional microscopic (10µm) images of the entire esophageal wall as it traverses the luminal organ via peristalsis or is retrieved by pulling up tether. As opposed to endoscopy, TCE procedure is non-invasive, doesn’t require patient sedation and mitigates sampling error by evaluating the microscopic structure of the entire esophagus. The merits of TCE make it a suitable device to investigate the microscopic natural history of BE in a longitudinal manner.
Here, we present our initial experience of a multicenter (5-site) clinical trial to study the microscopic natural history of BE. The TCE device used for the study is the new generation capsule with the ball lens optical configuration and a distal scan stepper motor, which provides 30µm (lateral) resolution and 40Hz imaging rate. The portable OCT imaging system is a custom in-house built swept source system and provides 7µm (axial) at a 100 kHz A-line rate with a center wavelength of ~1310 nm. To date, we have successfully enrolled 69 subjects at all sites (MGH: 33, Columbia University: 11, Kansas City VA: 10, Mayo Jacksonville: 8, Mayo Rochester: 7) and 59 have swallowed the capsule (85.5%). There have been no reported adverse events associated with TCE procedure. High-quality OCT images were reliably obtained from patients who swallowed the device, and BE tissues were identified by expert readers. Our initial experience with TCE in a multicenter study demonstrates that this technology is easy to use and efficient in multiple clinical settings. Completion of this longitudinal study is likely to provide new insights on the temporal progression of BE that may impact management strategies.
Upper endoscopy is a standard technique for imaging, sampling, and treating gastrointestinal tissue. Endoscopy is frequently requiring the subjects who undergo the procedure be consciously sedated. Sedation necessitates that the endoscopy procedure be conducted in a specialized setting to mitigate complications should they arise. Endoscopy is further problematic for infants and young children (aged 0-24 months) who sometimes need to be anesthetized. These issues motivate alternative methods for upper gastrointestinal tract visualization and biopsy that do not require conscious sedation/anesthesia. To address this need, we have developed a double lumen 6.5 Fr transnasal introduction catheter (TNIC). During transnasal insertion, real-time OCT imaging provides confirmation of the anatomical location of the device. Once in the stomach, a safe and high-density liquid metal fills a balloon at the distal tip of the TNIC, allowing it to passively transit through stomach into the small intestine. Once properly positioned, OCT-guided instruments for imaging and biopsy can be inserted through main lumen of the TNIC, performing many of the functions of conventional endoscopy and advanced endomicroscopy. To test the feasibility of the TNIC, we conducted a clinical study using the first version of the device in 4 unsedated normal volunteers. Results showed detailed OCT endomicroscopy images of the esophagi and duodena. These results suggest that TNIC may be an effective, less invasive method for the diagnosis of upper GI tract conditions.
Environmental enteric dysfunction (EED) is a pathological condition of the small intestine that is endemic to low- and middle-income countries (LMICs). EED is thought to interfere with nutrient absorption and enteropathogen exclusion, resulting in altered immune response, increased infection, and limited neurological and physical development. Biopsy of the small intestine is the current diagnostic gold standard for diagnosis yet is untenable due to lack of availability in these countries. Endoscopic biopsy is further problematic since EED-related stunting can only be reversed if diagnosed in the first two years of life when endoscopy must be conducted under anesthesia in advanced medical care settings. Thus, there is an unmet need for a minimally invasive technology for obtaining small intestinal biopsies in unsedated infants in LMICs. To address this need, we have developed an OCT image-guided trans-nasal cryobiopsy device. The device comprises a dual-lumen 1.2 mm outer diameter (OD) probe, terminated by a metal tip, through which Freon is injected. The device is introduced through the lumen of a novel liquid-metal transnasal imaging tube that passively transits to the small intestine. M-mode OCT image guidance is used to determine when the metal tip is in contact with the mucosa so that cryobiopsies may be efficiently acquired. We have conducted feasibility experiments using this device in 10 swine in vivo, demonstrating residual bleeding that is comparable to conventional excisional biopsy, tissue sampling volumes that are greater than or equal to those of conventional biopsy, and high-quality histopathology. These results suggest that this transnasal cryobiopsy technique may be suitable for infants in low-resource settings where EED is prevalent, due to its simplicity and its ability to be used in unsedated subjects.
Environmental enteric dysfunction (EED) is a poorly understood condition of the small intestine prevalent in low and middle income countries. This disease is believed to cause nutrient malabsorption and poor oral vaccine uptake, resulting in arrested neurological development and growth stunting in children that persists as they grow into adulthood. Optical coherence tomography (OCT) imaging of the small intestine can potentially capture some of the microstructural changes, such as villous blunting, in the small gut that accompany EED, and hence could potentially improve the understanding of EED and help in determining and monitoring the effectiveness of EED interventions. Notably, EED must be studied and diagnosed in infants, aged 0-24 months as this is the only window in which interventional strategies can reverse the disease. In order to address this need, we propose a trans-nasal OCT imaging technique for imaging the small intestine that may be suitable for low-resource settings owing to its simplicity, ease of administration, and implementation in unsedated infants. To demonstrate the potential of transnasal OCT intestinal imaging, we have created a 10 Fr transnasal OCT imaging probe and have submitted an IRB application for a first-in-human study using this probe to image the adult small intestine. We anticipate that the results from this pilot study will justify the development of a transnasal OCT intestinal imaging device for infants.
Tethered capsule endomicroscopy (TCE) is a new method for performing comprehensive microstructural OCT imaging of gastrointestinal (GI) tract in unsedated patients in a well-tolerated and cost-effective manner. These features of TCE bestow it with significant potential to improve the screening, surveillance and management of various upper gastrointestinal diseases. To achieve clinical adoption of this imaging technique, it is important to validate it with co-registered histology, the current diagnostic gold standard. One such method for co-registering OCT images with histology is laser cautery marking, previously demonstrated using a balloon-centering OCT catheter that operates in conjunction with sedated endoscopy. With laser marking, an OCT area of interest is identified on the screen and this target is marked in the patient by exposing adjacent tissue to laser light that is absorbed by water, creating superficial, visible marks on the mucosal surface. Endoscopy can then be performed after the device is removed and biopsies taken from the marks. In this talk, we will present the design of a tethered capsule laser marking device that uses a distal stepper motor to perform high precision (< 0.5 mm accuracy) laser targeting and high quality OCT imaging. Ex vivo animal tissue tests and pilot human clinical studies using this technology will be presented.
KEYWORDS: Optical coherence tomography, Esophagus, Tissues, In vivo imaging, Image segmentation, Data acquisition, Endoscopy, Biopsy, Intelligence systems, Imaging systems
Catheter-based Optical Coherence Tomography (OCT) devices allow real-time and comprehensive imaging of the human esophagus. Hence, they provide the potential to overcome some of the limitations of endoscopy and biopsy, allowing earlier diagnosis and better prognosis for esophageal adenocarcinoma patients. However, the large number of images produced during every scan makes manual evaluation of the data exceedingly difficult. In this study, we propose a fully automated tissue characterization algorithm, capable of discriminating normal tissue from Barrett’s Esophagus (BE) and dysplasia through entire three-dimensional (3D) data sets, acquired in vivo. The method is based on both the estimation of the scatterer size of the esophageal epithelial cells, using the bandwidth of the correlation of the derivative (COD) method, as well as intensity-based characteristics. The COD method can effectively estimate the scatterer size of the esophageal epithelium cells in good agreement with the literature. As expected, both the mean scatterer size and its standard deviation increase with increasing severity of disease (i.e. from normal to BE to dysplasia). The differences in the distribution of scatterer size for each tissue type are statistically significant, with a p value of < 0.0001. However, the scatterer size by itself cannot be used to accurately classify the various tissues. With the addition of intensity-based statistics the correct classification rates for all three tissue types range from 83 to 100% depending on the lesion size.
High resolution micro-optical coherence tomography (µOCT) technology has been demonstrated to be useful for imaging respiratory epithelial functional microanatomy relevant to the study of pulmonary diseases such as cystic fibrosis and COPD. We previously reported the use of a benchtop μOCT imaging technology to image several relevant respiratory epithelial functional microanatomy at 40 fps and at lateral and axial resolutions of 2 and 1.3μm, respectively. We now present the development of a portable μOCT imaging system with comparable optical and imaging performance, which enables the μOCT technology to be translated to the clinic for in vivo imaging of human airways.
Celiac disease (CD) affects around 1% of the global population and can cause serious long-term symptoms including malnutrition, fatigue, and diarrhea, amongst others. Despite this, it is often left undiagnosed. Currently, a tissue diagnosis of CD is made by random endoscopic biopsy of the duodenum to confirm the existence of microscopic morphologic alterations in the intestinal mucosa. However, duodenal endoscopic biopsy is problematic because the morphological changes can be focal and endoscopic biopsy is plagued by sampling error. Additionally, tissue artifacts can also an issue because cuts in the transverse plane can make duodenal villi appear artifactually shortened and can bias the assessment of intraepithelial inflammation. Moreover, endoscopic biopsy is costly and poorly tolerated as the patient needs to be sedated to perform the procedure.
Our lab has previously developed technology termed tethered capsule OCT endomicroscopy (TCE) to overcome these diagnostic limitations of endoscopy. TCE involves swallowing an optomechanically-engineered pill that generates 3D images of the GI tract as it traverses the lumen of the organ via peristalsis, assisted by gravity. In several patients we have demonstrated TCE imaging of duodenal villi, however the current TCE device design is not optimal for CD diagnosis as the villi compress when in contact with the smooth capsule’s wall. In this work, we present methods for structuring the outer surface of the capsule to improve the visualization of the villi height and crypt depth. Preliminary results in humans suggest that new TCE capsule enables better visualization of villous architecture, making it possibly to comprehensively scan the entire duodenum to obtain a more accurate tissue diagnosis of CD.
Environmental enteric dysfunction (EED) is a poorly understood disease of the small intestine that causes nutrient malabsorption in children, predominantly from low and middle income countries. The clinical importance of EED is neurological and growth stunting that remains as the child grows into adulthood. Tethered capsule endomicroscopy (TCE) has the potential to improve the understanding of EED and could be used to determine the effectiveness of EED interventions. TCE in the adult esophagus and the duodenum has been demonstrated for Barrett`s esophagus and celiac disease diagnosis, respectively. While adult subjects can independently swallow these capsules, it is likely that infants will not, and, as a result, new strategies for introducing these devices in young children aged 0.5-2 years need to be investigated. Our first approach will be to introduce the TCE devices in infants under the aid of endoscopic guidance. To determine the most effective method, we have tested endoscopic approaches for introducing TCE devices into the small intestine of living swine. These methods will be compared and contrasted to discuss the most effective means for endoscopic tethered capsule introduction into the small intestine.
Endoscopy, the current standard of care for the diagnosis of upper gastrointestinal (GI) diseases, is not ideal as a screening tool because it is costly, necessitates a team of medically trained personnel, and typically requires that the patient be sedated. Endoscopy is also a superficial macroscopic imaging modality and therefore is unable to provide detailed information on subsurface microscopic structure that is required to render a precise tissue diagnosis. We have overcome these limitations through the development of an optical coherence tomography tethered capsule endomicroscopy (OCT-TCE) imaging device. The OCT-TCE device has a pill-like form factor with an optically clear wall to allow the contained opto-mechanical components to scan the OCT beam along the circumference of the esophagus. Once swallowed, the OCT-TCE device traverses the esophagus naturally via peristalsis and multiple cross-sectional OCT images are obtained at 30-40 μm lateral resolution by 7 μm axial resolution. While this spatial resolution enables differentiation of squamous vs columnar mucosa, crucial microstructural features such as goblet cells (~10 μm), which signify intestinal metaplasia in BE, and enlarged nuclei that are indicative of dysplasia cannot be resolved with the current OCT-TCE technology.
In this work we demonstrate a novel design of a high lateral resolution OCT-TCE device with an extended depth of focus (EDOF). The EDOF is created by use of self-imaging wavefront division multiplexing that produces multiple focused modes at different depths into the sample. The overall size of the EDOF TCE is similar to that of the previous OCT-TCE device (~ 11 mm by 26 mm) but with a lateral resolution of ~ 8 μm over a depth range of ~ 2 mm. Preliminary esophageal and intestinal imaging using these EDOF optics demonstrates an improvement in the ability to resolve tissue morphology including individual glands and cells. These results suggest that the use of EDOF optics may be a promising avenue for increasing the accuracy of OCT-TCE for the diagnosis of upper GI diseases.
Due to the relatively high cost and inconvenience of upper endoscopic biopsy and the rising incidence of esophageal adenocarcinoma, there is currently a need for an improved method for screening for Barrett’s esophagus. Ideally, such a test would be applied in the primary care setting and patients referred to endoscopy if the result is suspicious for Barrett’s. Tethered capsule endomicroscopy (TCE) is a recently developed technology that rapidly acquires microscopic images of the entire esophagus in unsedated subjects. Here, we present our first experience with clinical translation and feasibility of TCE in a primary care practice. The acceptance of the TCE device by the primary care clinical staff and patients shows the potential of this device to be useful as a screening tool for a broader population.
While endoscopy is the most commonly used modality for diagnosing upper GI tract disease, this procedure usually requires patient sedation that increases cost and mandates its operation in specialized settings. In addition, endoscopy only visualizes tissue superfically at the macroscopic scale, which is problematic for many diseases that manifest below the surface at a microscopic scale. Our lab has previously developed technology termed tethered capsule OCT endomicroscopy (TCE) to overcome these diagnostic limitations of endoscopy. The TCE device is a swallowable capsule that contains optomechanical components that circumferentially scan the OCT beam inside the body as the pill traverses the organ via peristalsis. While we have successfully imaged ~100 patients with the TCE device, the optics of our current device have many elements and are complex, comprising a glass ferrule, optical fiber, glass spacer, GRIN lens and prism. As we scale up manufacturing of this device for clinical translation, we must decrease the cost and improve the manufacturability of the capsule’s optical configuration.
In this abstract, we report on the design and development of simplificed TCE optics that replace the GRIN lens-based configuration with an angle-polished ball lens design. The new optics include a single mode optical fiber, a glass spacer and an angle polished ball lens, that are all fusion spliced together. The ball lens capsule has resolutions that are comparable with those of our previous GRIN lens configuration (30µm (lateral) × 7 µm (axial)). Results in human subjects show that OCT-based TCE using the ball lens not only provides rapid, high quality microstructural images of upper GI tract, but also makes it possible to implement this technology inexpensively and on a larger scale.
Photodynamic therapy (PDT) of cancer works via direct cytotoxicity, causing damage to tumor vasculature and
stimulating the body’s anti-tumor immune response. PDT outcome depends on the parameters used; therefore an in vivo
tumor response monitoring system is useful for optimization of the treatment protocol. The combined use of diffuse
optical spectroscopy and diffuse correlation spectroscopy allows us to measure the tissue oxygen saturation (StO2) and
relative blood flow (rBF) in tumors. These parameters were measured before and after PDT in mouse tumor models and
were calculated as ratios relative to the baseline in each tumor (rStO2 and rBF). Readings were also measured in drugonly
control tumors. In responders (mice with tumor eradication), significant PDT-induced decreases in both rStO2 and
rBF levels were observed at 3h post-PDT. The rStO2 and rBF readings in these mice remained low until 48h post-PDT,
with recovery of these parameters to baseline values observed 2 weeks after PDT. In non-responders (mice with partial
or no response), the rStO2 and rBF levels decreased less sharply at 3h post-PDT, and the rBF values returned toward
baseline values at 48h post-PDT. By comparison, the rStO2 and rBF readings in drug-only control tumors showed only
fluctuations about the baseline values. Thus tumor response can be predicted as early as 3h post-PDT. Recovery or
sustained decreases in rStO2 and rBF up till 48h post-PDT were correlated to long-term tumor control. Diffuse optical
measurements can thus facilitate early assessment of tumor response to PDT to aid in treatment planning.
Diffuse correlation spectroscopy (DCS) is an emerging noninvasive technique that probes the deep tissue blood flow, by using the time-averaged intensity autocorrelation function of the fluctuating diffuse reflectance signal. We present a fast Fourier transform (FFT)-based software autocorrelator that utilizes the graphical programming language LabVIEW (National Instruments) to complete data acquisition, recording, and processing tasks. The validation and evaluation experiments were conducted on an in-house flow phantom, human forearm, and photodynamic therapy (PDT) on mouse tumors under the acquisition rate of ∼400 kHz . The software autocorrelator in general has certain advantages, such as flexibility in raw photon count data preprocessing and low cost. In addition to that, our FFT-based software autocorrelator offers smoother starting and ending plateaus when compared to a hardware correlator, which could directly benefit the fitting results without too much sacrifice in speed. We show that the blood flow index (BFI) obtained by using a software autocorrelator exhibits better linear behavior in a phantom control experiment when compared to a hardware one. The results indicate that an FFT-based software autocorrelator can be an alternative solution to the conventional hardware ones in DCS systems with considerable benefits.
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