SignificanceThe shortwave infrared (SWIR, ∼900 to 2000 nm) holds promise for label-free measurements of water and lipid content in thick tissue, owed to the chromophore-specific absorption features and low scattering in this range. In vivo water and lipid estimations have potential applications including the monitoring of hydration, volume status, edema, body composition, weight loss, and cancer. To the best of our knowledge, there are currently no point-of-care or wearable devices available that exploit the SWIR wavelength range, limiting clinical and at-home translation of this technology.AimTo design and fabricate a diffuse optical wearable SWIR probe for water and lipid quantification in tissue.ApproachSimulations were first performed to confirm the theoretical advantage of SWIR wavelengths over near infrared (NIR). The probe was then fabricated, consisting of light emitting diodes at three wavelengths (980, 1200, 1300 nm) and four source-detector (S-D) separations (7, 10, 13, 16 mm). In vitro validation was then performed on emulsion phantoms containing varying concentrations of water, lipid, and deuterium oxide (D2O). A deep neural network was developed as the inverse model for quantity estimation.ResultsSimulations indicated that SWIR wavelengths could reduce theoretical water and lipid extraction errors from ∼6 % to ∼1 % when compared to NIR wavelengths. The SWIR probe had good signal-to-noise ratio (>32 dB up to 10 mm S-D) and low drift (<1.1 % up to 10 mm S-D). Quantification error in emulsion phantoms was 2.1 ± 1.1 % for water and −1.2 ± 1.5 % for lipid. Water estimation during a D2O dilution experiment had an error of 3.1 ± 3.7 % .ConclusionsThis diffuse optical SWIR probe was able to quantify water and lipid contents in vitro with good accuracy, opening the door to human investigations.
We present an update on our high optode-density continuous-wave (CW) wearable diffuse optical device for the investigation of hemodynamic responses of locally advanced breast tumors during neoadjuvant chemotherapy (NAC). The device consists of a rigid-flex substrate with 32 LEDs at two wavelengths and 16 detectors. Measurements on spatially-complex flow phantoms have validated the ability to reconstruct temporal spatial absorption contrast. Preliminary results from a healthy volunteer study (N=4 volunteers) indicate that paced breathing hemodynamics can be quantified in healthy subjects, and initial clinical measurements (N=3) suggest that these hemodynamics may reveal strong tumor contrast in some instances.
Significance: Diffuse optical imaging (DOI) provides in vivo quantification of tissue chromophores such as oxy- and deoxyhemoglobin (HbO2 and HHb, respectively). These parameters have been shown to be useful for predicting neoadjuvant treatment response in breast cancer patients. However, most DOI devices designed for the breast are nonportable, making frequent longitudinal monitoring during treatment a challenge. Furthermore, hemodynamics related to the respiratory cycle are currently unexplored in the breast and may have prognostic value.
Aim: To design, fabricate, and validate a high optode-density wearable continuous wave diffuse optical probe for the monitoring of breathing hemodynamics in breast tissue.
Approach: The probe has a rigid-flex design with 16 dual-wavelength sources and 16 detectors. Performance was characterized on tissue-simulating phantoms, and validation was performed through flow phantom and cuff occlusion measurements. The breasts of N = 4 healthy volunteers were measured while performing a breathing protocol.
Results: The probe has 512 unique source–detector (S-D) pairs that span S-D separations of 10 to 54 mm. It exhibited good performance characteristics: μa drift of 0.34%/h, μa precision of 0.063%, and mean SNR ≥ 24 dB up to 41 mm S-D separation. Absorption contrast was detected in flow phantoms at depths exceeding 28 mm. A cuff occlusion measurement confirmed the ability of the probe to track expected hemodynamics in vivo. Breast measurements on healthy volunteers during paced breathing revealed median signal-to-motion artifact ratios ranging from 8.1 to 8.7 dB. Median ΔHbO2 and ΔHHb amplitudes ranged from 0.39 to 0.67 μM and 0.08 to 0.12 μM, respectively. Median oxygen saturations at the respiratory rate ranged from 82% to 87%.
Conclusions: A wearable diffuse optical probe has been designed and fabricated for the measurement of breast tissue hemodynamics. This device is capable of quantifying breathing-related hemodynamics in healthy breast tissue.
We present an update on our high optode-density continuous-wave (CW) wearable diffuse optical device for the investigation of hemodynamic responses of locally advanced breast tumors during neoadjuvant chemotherapy (NAC). The device consists of a rigid-flex substrate with 32 LEDs at two wavelengths and 16 detectors. Measurements during a cuff occlusion indicate that the probe can quantify hemodynamics temporally, and measurements on spatially-complex flow phantoms have validated the ability to reconstruct spatial contrast. A normal volunteer study is currently ongoing, and preliminary results (N=7 volunteers) indicate that paced breathing hemodynamics can be quantified in healthy subjects.
Oxygen plays a role in many aspects of tumor biology such as metastasis, drug resistance, and angiogenesis. Chaotic vasculature and cell signaling can lead to segments of the tumor that are oxygen-rich while neighboring regions can be severely hypoxic. Previous work has shown that this spatial variation is a dynamic process, but the precise spatio-temporal evolution is poorly understood. Spatial Frequency Domain Imaging (SFDI) is an emerging technique for measuring wide-field maps of absolute concentrations of tissue chromophores. Here we present an SFDI device capable of acquiring hyperspectral (~10 wavelengths) SFDI images at relatively high speeds (0.1 Hz). A Quartz Tungsten Halogen lamp source is used as the input to a Czerny-Turner monochromator. Instead of an exit slit, a digital micromirror device (DMD) is used to select any wavelength within the range of the DMD. The monochromatic beam is directed onto a second DMD which spatially modulates the light incident on the sample. This system is highly flexible and allows for rapid selection and projection of any wavelength from 500-1800 nm. We verified the accuracy and precision of the instrument on a series of tissue mimicking optical phantoms, and collected what we believe to be the first wide-field, time-resolved measurement of the spatio-temporal dynamics of a xenograft breast tumor in a mouse model in vivo. These measurements will further our understanding of tumor oxygen dynamics for use in developing more effective drug treatment schedules, and discovery of novel drug targets.
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.