Upcoming 2025 SPIE Conference Presentations

The Optics at Martinos group is excited to attend and present at the SPIE Photonics West Conference on January 25th – January 30th, 2025 in San Francisco, CA! We have many conference presentations and posters to look out for, including:

25 January 2025 • 3:50 PM – 4:10 PM PST | Moscone South, Room 105 (Level 1 Lobby)
SPIE Conference 13302: Clinical and Translational Neurophotonics 2025

Optical functional brain imaging has typically been performed with functional near-infrared spectroscopy (fNIRS). While fNIRS measures hemoglobin concentration, diffuse correlation spectroscopy (DCS) can provide additional information through measurement of cerebral blood flow. Recent technological improvements in DCS, specifically interferometric detection, enhance signal-to-noise ratio (SNR) and enable parallelized measurements. We developed a multi-channel perfusion imaging system using long-wavelength interferometric DCS (LW-iDCS) at 1064 nm. This study compares cerebral blood flow responses measured by LW-iDCS with hemoglobin concentration changes measured by fNIRS during motor and cognitive tasks. Results highlight differences in hemodynamic responses, suggesting enhanced metabolic response insights from blood flow measurements.

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25 January 2025 • 4:35 PM – 4:55 PM PST | Moscone South, Room 304 (Level 3)
SPIE Conference 13318: Dynamics and Fluctuations in Biomedical Photonics XXII

Diffuse correlation spectroscopy (DCS) is a noninvasive technique used to estimate tissue blood flow through the analysis of scattered coherent light. While well suited to enable continuous cerebral blood flow monitoring, traditional DCS has limited signal-to-noise ratio (SNR) at source-detector separations sensitive to cerebral physiology. In this work we combine a recently developed advanced DCS technique, pathlength selective interferometric DCS (PaLS-iDCS) with multiwavelength acquisition to allow for the pathlength specific estimation of blood flow, hemoglobin concentration, hemoglobin saturation, and the metabolic rate of oxygen consumption (MRO2). The advances provided by multiwavelength acquisition greatly improve cerebral hemodynamic characterization.

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25 January 2025 • 4:50 PM – 5:10 PM PST | Moscone South, Room 105 (Level 1 Lobby)
SPIE Conference 13302: Clinical and Translational Neurophotonics 2025

Diffuse correlation spectroscopy (DCS) can quantify blood flow in the human brain and can be used to estimate critical closing pressure (CrCP) and thus infer on intracranial pressure. To quantify cerebral blood flow at a 50Hz and 3.5cm source-detector separation, we designed a DCS system operating at 1064nm with a multi-illumination probe using 3 sources and four SNSPD-based colocalized detection channels with interferometric detection. We present measurements performed in 10 participants using the designed instrument, a reference DCS system (850nm, 25mm SD separation), and bi-lateral transcranial doppler ultrasound, together with blood pressure and electrocardiogram for CrCP estimation.

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25 January 2025 • 5:15 PM – 5:35 PM PST | Moscone South, Room 304 (Level 3)
SPIE Conference 13314: Dynamics and Fluctuations in Biomedical Photonics XXII

Speckle contrast optical spectroscopy (SCOS) is a camera-based diffuse optical technique that is increasingly being applied to measure human cerebral blood flow (CBF) noninvasively. Due to massively parallel speckle detection on the camera, SCOS is expected to offer higher contrast-to-noise ratio (CNR) in human CBF measurements than the current state-of-the-art technique of diffuse correlation spectroscopy (DCS). There is a lack of comparison studies between DCS and SCOS at larger (i.e. >2 cm) source-detector separations (SDS) where brain sensitivity is higher and biases from camera noise become greater in SCOS due to reduced photon flux. We performed concurrent SCOS and DCS measurements at 3 cm SDS during induced changes in human CBF to validate SCOS against DCS and evaluate the impact of SCOS’s CNR advantage.
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26 January 2025 • 8:00 AM – 8:20 AM PST | Moscone South, Room 105 (Level 1 Lobby)
SPIE Conference 13302: Clinical and Translational Neurophotonics 2025

We present data from long-term continuous optical monitoring of patients with subarachnoid hemorrhage, a rare medical condition requiring treatment in intensive care to prevent brain damage from complications such as vasospasm. Diffuse correlation spectroscopy (DCS) data was collected at three separations, and clinical data including ECG data and arterial blood pressure were collected from clinical monitors. Drug administration times were collected from the medical record. We show that DCS is a viable method for long-term continuous bedside monitoring and, based on treatment-induced physiological changes, that systemic blood pressure is not a suitable surrogate marker for brain blood flow.

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27 January 2025 • 10:40 AM – 11:10 AM PST | Moscone South, Room 213 (Level 2)
SPIE Conference 13314: Optical Tomography and Spectroscopy of Tissue XVI

Peripheral edema occurs due to various causes including inflammation, injury or cardiovascular diseases. Importantly, it is a marker of decompensation in patients with heart failure. Timely detection of edema development prior to overt symptom development requires continuous monitoring. We are developing a multi-wavelength wearable derived from the previously demonstrated FlexNIRS platform to assess the tissue water fraction. We show validation measurements of discrete wavelength, multi-distance CW-NIRS measurements against frequency-domain NIRS and broadband spectroscopy using both a subset of the spectrometer measurements and a custom multi-wavelength LED module based wearable prototype. Results are reported from both phantoms and in vivo measurements.

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28 January 2025 • 11:20 AM – 11:40 AM PST | Moscone South, Room 213 (Level 2)
SPIE Conference 13314: Optical Tomography and Spectroscopy of Tissue XVI

Near-infrared diffuse optical tomography (DOT) is a promising functional modality for breast cancer imaging; however, the clinical translation of DOT is hampered by technical limitations. Specifically, conventional finite element method (FEM)-based image reconstruction methods are time-consuming and ineffective in recovering full contrast, especially in small lesions typically seen in the diagnostic setting. To address this, in our prior work, a three-part deep convolutional neural network (DNN)-based model comprised of Fully connected layers, followed by a convolutional encoder-Decoder, and a U-Net (a.k.a. FDU-Net) was developed for fast, end-to-end 3D DOT image reconstruction. In this work, we further expanded FDU-Net to utilize high-resolution structural images as an additional input in a multi-channel U-Net. Through benchmark comparisons with conventional finite element-based methods (FEM) and previously published DNN models using 250 synthetic cases, the FDmU-Net demonstrated far superior accuracy in lesion localization and further enhancement in contrast recovery while maintaining high overall image quality in small 8-mm diameter inclusion cases.