SignificanceColor differences between healthy and diseased tissue in the gastrointestinal (GI) tract are detected visually by clinicians during white light endoscopy; however, the earliest signs of cancer are often just a slightly different shade of pink compared to healthy tissue making it hard to detect. Improving contrast in endoscopy is important for early detection of disease in the GI tract during routine screening and surveillance.AimWe aim to target alternative colors for imaging to improve contrast using custom multispectral filter arrays (MSFAs) that could be deployed in an endoscopic “chip-on-tip” configuration.ApproachUsing an open-source toolbox, Opti-MSFA, we examined the optimal design of MSFAs for early cancer detection in the GI tract. The toolbox was first extended to use additional classification models (k-nearest neighbor, support vector machine, and spectral angle mapper). Using input spectral data from published clinical trials examining the esophagus and colon, we optimized the design of MSFAs with three to nine different bands.ResultsWe examined the variation of the spectral and spatial classification accuracies as a function of the number of bands. The MSFA configurations tested showed good classification accuracies when compared to the full hyperspectral data available from the clinical spectra used in these studies.ConclusionThe ability to retain good classification accuracies with a reduced number of spectral bands could enable the future deployment of multispectral imaging in an endoscopic chip-on-tip configuration using simplified MSFA hardware. Further studies using an expanded clinical dataset are needed to confirm these findings.
Here, we explore the potential benefits of extracting hemoglobin oxygenation metrics using multispectral imaging (MSI) in nailfold capillaroscopy for systemic sclerosis (SSc) patients. We used a nine-band multispectral camera to capture images of the nail bed from SSc patients (n=10) and healthy controls (n=12). Spectral analysis and machine learning classification were employed to examine systematic changes between healthy controls and SSc patients. The results demonstrate differences in spectra and promising accuracy in classification, with further work needed to extract oxygenation values and improve signal-to-noise ratio. MSI shows potential for improving sensitivity of nailfold capillaroscopy and detection of changes in early disease.
Tissue-mimicking phantoms are vital for the calibration of imaging systems. Blood oxygenation is an important physiological parameter that spectral imaging devices can measure, motivating the need for blood phantoms with variable oxygenation. We present a soft lithography method for fabricating blood flow phantoms that enable control of channel size and blood oxygenation. Channel size was varied during the fabrication process. Oxygenation was varied by chemical oxygenation and deoxygenation of horse blood flowing in the phantom. The spectral properties of the phantoms were evaluated using a narrowband nailfold capillaroscopy system. The resulting phantoms yield a flexible approach for spectral imaging calibration.
The optimal design and development of multispectral cameras could potentially improve the diagnosis of esophageal and colon cancer during routine screening and surveillance programs. We used an open-source Python toolbox Opti-MSFA and spectral data from clinical studies to determine the optimal spectral bands for inclusion in a snap-shot multispectral imaging system based on multispectral filter arrays (MSFAs) atop a CMOS image sensor. We emulated the feasibility of the proposed optimization method via synthetic datasets, which shows that the optimized MSFAs allow the accurate spectral unmixing of blood oxygen levels. The next steps are to implement the spectral imaging system with optimized MSFAs and demonstrate that the selected spectral bands are versatile in clinical trials.
SignificanceThe capillaries are the smallest blood vessels in the body, typically imaged using video capillaroscopy to aid diagnosis of connective tissue diseases, such as systemic sclerosis. Video capillaroscopy allows visualization of morphological changes in the nailfold capillaries but does not provide any physiological information about the blood contained within the capillary network. Extracting parameters such as hemoglobin oxygenation could increase sensitivity for diagnosis and measurement of microvascular disease progression.AimTo design, construct, and test a low-cost multispectral imaging (MSI) system using light-emitting diode (LED) illumination to assess relative hemoglobin oxygenation in the nailfold capillaries.ApproachAn LED ring light was first designed and modeled. The ring light was fabricated using four commercially available LED colors and a custom-designed printed circuit board. The experimental system was characterized and results compared with the illumination model. A blood phantom with variable oxygenation was used to determine the feasibility of using the illumination-based MSI system for oximetry. Nailfold capillaries were then imaged in a healthy subject.ResultsThe illumination modeling results were in close agreement with the constructed system. Imaging of the blood phantom demonstrated sensitivity to changing hemoglobin oxygenation, which was in line with the spectral modeling of reflection. The morphological properties of the volunteer capillaries were comparable to those measured in current gold standard systems.ConclusionsLED-based illumination could be used as a low-cost approach to enable MSI of the nailfold capillaries to provide insight into the oxygenation of the blood contained within the capillary network.
Significance: Measurement and imaging of hemoglobin oxygenation are used extensively in the detection and diagnosis of disease; however, the applied instruments vary widely in their depth of imaging, spatiotemporal resolution, sensitivity, accuracy, complexity, physical size, and cost. The wide variation in available instrumentation can make it challenging for end users to select the appropriate tools for their application and to understand the relative limitations of different methods.Aim: We aim to provide a systematic overview of the field of hemoglobin imaging and sensing.Approach: We reviewed the sensing and imaging methods used to analyze hemoglobin oxygenation, including pulse oximetry, spectral reflectance imaging, diffuse optical imaging, spectroscopic optical coherence tomography, photoacoustic imaging, and diffuse correlation spectroscopy.Results: We compared and contrasted the ability of different methods to determine hemoglobin biomarkers such as oxygenation while considering factors that influence their practical application.Conclusions: We highlight key limitations in the current state-of-the-art and make suggestions for routes to advance the clinical use and interpretation of hemoglobin oxygenation information.
We present a method for designing and fabricating 'HyperPixels': pixel filter arrays with custom spectral transmission properties that enable efficient imaging of specific chromophores or fluorophores. Multispectral imaging typically targets particular spectral bands to uncover the spectral properties of tissue in combination with spatial resolution. Unmixing spectral properties can uncover the type and quantity of chromophores or fluorophores due to their unique spectral absorption or emission. Pixelated filter arrays atop imaging sensors are low-cost techniques used to achieve multispectral imaging. Typically, the filter pixels exhibit bandpass spectral behaviour, allowing only a fraction of the incident light to reach the sensor. As a result, narrowband filter pixels trade off high spectral resolution with optical power loss. A way to avoid this issue and improve the signal to noise ratio (SNR) for individual targets is to use a filter array where individual pixels are matched to a target chemical compound's reflectance or emission spectrum. Simulations show a >5-fold improvement in SNR under realistic noise conditions. These matched optical filters can also reduce the complexity of software or hardware spectral unmixing algorithms, offering the potential for real-time imaging of target compounds. We present a method for tailoring spectral transmission of individual pixels by building HyperPixels comprising multiple Fabry-Perot resonator subpixels with varying bandpass properties (FWHM = approximately 50-60 nm, thicknesses 75-150 nm) that collectively have the desired transmission spectrum. We used a numerical optimization process to design filter arrays for simultaneous detection of methylene blue and indocyanine green, commonly used in cancer diagnostics by clinicians. We then fabricated filters for indocyanine green detection using grayscale lithography with pixel sizes down to 5 μm and individual subpixels down to 0.5 μm and characterized them for their spectral properties.
Nailfold capillaroscopy is a technique for imaging the capillary bed in the finger nailfold, that is used in the diagnosis of scleroderma. Knowledge of the capillary oxygenation profile would be a substantial advantage in disease evaluation. A compact, low-cost LED-illuminated capillaroscopy system was conceived based on inexpensive parts and optical hardware. The system uses a compact Raspberry Pi to control a custom-designed LED ring light, with white-light LEDs interleaved with three narrowband LEDs, and a Raspberry Pi camera. Capillary visualisation and distinction of haemoglobin contrast is demonstrated, suggesting future promise for application of multispectral nailfold capillaroscopy in low-resource settings.
Nailfold capillaroscopy is a technique for imaging the capillary bed in the finger nailfold, which is used in the diagnosis of scleroderma. Knowledge of the capillary oxygenation profile would be advantageous in disease evaluation due to the suspected involvement of hypoxia in causing fibrosis. A hyperspectral nailfold capillaroscopy system with narrowband illumination provided by a supercontinuum laser and acousto-optic tuneable filter was created to enable spectral analysis of the nailfold. Hyperspectral imaging (HSI) data from 500-595 nm was analysed to extract image quality metrics, which suggested HSI oximetry holds promise for understanding how rheumatic diseases affect oxygenation of the nailfold.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.