Calcium phosphate glass based single-mode and multi-mode bioresorbable optical fibers were in-house manufactured. Ex-vivo studies were then conducted to test the suitability of these fibers for time gated diffuse optics spectroscopy, photodynamic therapy and diffuse correlation spectroscopy applications which can be respectively employed for the diagnosis, treatment, and monitoring of malignant tissues. The results demonstrated the potential of calcium phosphate glass-based fiber optic devices towards the realization of an implantable multi-functional class of devices with functionalities ranging from cancer detection to monitoring of the healing process all integrated into a single bioresorbable platform.
Acknowledgement: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 860185
Bioresorbable materials have gained interest for implantable optical components such as fibers for medical devices and have been demonstrated as suitable to perform diffuse optical measurements. In this work, we demonstrate interstitial, broadband, time-domain diffuse optical spectroscopy measurements using bioresorbable fibers, by employing a single-photon avalanche diode operated in an ultrafast time-gate mode for photon detection. Using tissue equivalent liquid phantoms, we test the system absorption linearity as per the MEDPHOT protocol and demonstrate the scattering independent absorption retrieval of the water spectrum in the 600-920 nm range. Consequently, we also attempt to distinguish the spectral changes due to the presence of optically denser speck inclusion in a tissue equivalent liquid phantom.
SignificanceInterstitial fiber-based spectroscopy is gaining interest for real-time in vivo optical biopsies, endoscopic interventions, and local monitoring of therapy. Different from other photonics approaches, time-domain diffuse optical spectroscopy (TD-DOS) can probe the tissue at a few cm distance from the fiber tip and disentangle absorption from the scattering properties. Nevertheless, the signal detected at a short distance from the source is strongly dominated by the photons arriving early at the detector, thus hampering the possibility of resolving late photons, which are rich in information about depth and absorption.AimTo fully benefit from the null-distance approach, a detector with an extremely high dynamic range is required to effectively collect the late photons; the goal of our paper is to test its feasibility to perform TD-DOS measurements at null source–detector separations (NSDS).ApproachIn particular, we demonstrate the use of a superconducting nanowire single photon detector (SNSPD) to perform TD-DOS at almost NSDS ( ≈ 150 μm ) by exploiting the high dynamic range and temporal resolution of the SNSPD to extract late arriving, deep-traveling photons from the burst of early photons.ResultsThis approach was demonstrated both on Monte Carlo simulations and on phantom measurements, achieving an accuracy in the retrieval of the water spectrum of better than 15%, spanning almost two decades of absorption change in the 700- to 1100-nm range. Additionally, we show that, for interstitial measurements at null source–detector distance, the scattering coefficient has a negligible effect on late photons, easing the retrieval of the absorption coefficient.ConclusionsUtilizing the SNSPD, broadband TD-DOS measurements were performed to successfully retrieve the absorption spectra of the liquid phantoms. Although the SNSPD has certain drawbacks for use in a clinical system, it is an emerging field with research progressing rapidly, and this makes the SNSPD a viable option and a good solution for future research in needle guided time-domain interstitial fiber spectroscopy.
We demonstrate a novel realization of Interstitial fiber, broadband, Time Domain Diffuse Optical Spectroscopy (TD-DOS) in Null Source-Detector separation (NSDS) approach without temporal gating, by using a Super-conducting Nanowire single photon detector (SNSPD) for acquisition. We test its feasibility by performing Monte Carlo simulations and comparing the absorption retrieval of the SNSPD with an ideal scenario and a standard Silicon Photomultiplier (SiPM). Consequently, as per the MEDPHOT protocol, we test experimentally, the absorption linearity of the system on tissue-equivalent liquid phantoms and demonstrate the scattering independent retrieval of the absorption spectrum of water using Intralipid phantoms in the wavelength range of 600-1100 nm.
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.