Mapping polarization-sensitive optical coherence tomography and ultra-high-field diffusion MRI in the macaque brain

April 26, 2024 | Neurology

Christophe Lenglet, Essa Yacoub, Hamza Farooq, Jan Zimmermann, Kamil Ugurbil, Marilyn Yeatts, Matthew Johnson, Noam Harel, Pramod K. Pisharady, Sarah R. Heilbronner, Steen Moeller, taner akkin

This paper provides comparisons between microstructure and two-dimensional fiber orientations measured optically using polarization-sensitive optical coherence tomography (PS-OCT) and those estimated from ultra-high-field diffusion MRI (dMRI) at 10.5T in the macaque brain. The PS-OCT imaging is done at an in-plane resolution of ~10 microns in and around the thalamus. Whole brain dMRI is acquired at an isotropic resolution of 0.75 mm. We provide comparisons between cross-polarization and optical orientation from PS-OCT with the fractional anisotropy and two-dimensional orientations extracted from dMRI using a diffusion tensor model. The orientations from PS-OCT are also extracted computationally using a structure tensor. Additionally, we demonstrate the utility of mesoscale, PS-OCT imaging in improving the MRI resolution by learning the mapping between these contrasts using a super-resolution Generative Adversarial Network.

Structural analysis of the female reptile reproductive system by micro-computed tomography and optical coherence tomography

April 23, 2024 | Developmental Biology | Baylor College of Medicine, University of Texas MD Anderson Cancer Center

Bonnie K. Kircher, Deirdre M. Scully, Irina V. Larina, Michaela A. McCown, Richard R. Behringer

Volumetric data provide unprecedented structural insight to the reproductive tract and add vital anatomical context to the relationships between organs. The morphology of the female reproductive tract in non-avian reptiles varies between species, corresponding to a broad range of reproductive modes and providing valuable insight to comparative investigations of reproductive anatomy. However, reproductive studies in reptilian models, such as the brown anole studied here, have historically relied on histological methods to understand the anatomy. While these methods are highly effective for characterizing the cell types present in each organ, histological methods lose the 3D relationships between images and leave the architecture of the organ system poorly understood. We present the first comprehensive volumetric analyses of the female brown anole reproductive tract using two non-invasive, non-destructive imaging modalities: micro-computed tomography (microCT) and optical coherence to...

Updated with memorial fund information: Biomedical Engineering Chair Joseph Izatt Dies

April 23, 2024 | Other News | Duke University

Joseph A. Izatt

Joseph Izatt, the Michael J. Fitzpatrick Professor of Engineering and chair of Duke’s Department of Biomedical Engineering (BME), passed away on Sunday, April 7. Since joining Duke in 2001, Izatt served the university through dedicated service to his students and colleagues, and as a pioneering researcher. During his tenure as chair of Duke BME, he championed the successes of all within the community and worked with faculty, staff and students to ensure the department supported their goals. In a message Monday to the Duke Engineering community, Pratt School Dean Jerome Lynch celebrated Izatt’s career and leadership. “He was an exceptionally thoughtful leader who weighed every decision with a care that originated with his deep love for the BME community. The integrity and humility he brought as a school leader will be missed.” Biomedical engineering chair Joseph Izatt Izatt was a skilled researcher and inventor who played a foundational role in the development of optical cohe...

Multi-channel delay sampling to extend imaging depth in high-speed swept-source OCT systems

April 22, 2024 | General Technology | Praevium Research, University of Washington

Christopher Burger, Jian Liu, Ruikang K. Wang, Vijaysekhar Jayaraman, Yaping Shi, Zhaoyu Gong

We present a multi-channel delay sampling method to extend imaging depth in high-speed swept-source optical coherence tomography (SS-OCT). A balanced detector captures interference signals, converting them into electrical signals, which are then split into N channels, each with fixed time delays determined by the length of electrical cables. Then, they are digitized by an N-channel acquisition card. A calibration procedure is utilized to compensate for non-uniform phase shifts resulting from fixed time delays. The N-channel signals are merged in k-space and resampled to obtain a linearized spectrum, which increases the sampling rate by a factor of N, thereby extending the ranging distance by N times, all without altering k-clock triggering or sacrificing other imaging performance. The signal-to-noise ratio and sensitivity within the original depth range also have been enhanced. This advancement contributes to the improvement of the overall performance of SS-OCT systems.

Using optical coherence tomography to optimize Mohs micrographic surgery

April 18, 2024 | Dermatology | University of Illinois-Chicago

Carolina Puyana, Jenna Lee, Julia Roma May, Kamran Avanaki, Maria Tsoukas, Rayyan Manwar, Sasha Kravets, Sruti S. Akella, Vassilios Dimitropolous

Mohs micrographic surgery (MMS) is considered the gold standard for treating high-risk cutaneous basal cell carcinoma (BCC), but is expensive, time-consuming, and can be unpredictable as to how many stages will be required or how large the final lesion and corresponding surgical defect will be. This study is meant to investigate whether optical coherence tomography (OCT), a highly researched modality in dermatology, can be used preoperatively to map out the borders of BCC, resulting in fewer stages of MMS or a smaller final defect. In this prospective study, 22 patients with BCC undergoing surgical excision were enrolled at a single institution. All patients had previously received a diagnostic biopsy providing confirmation of BCC and had been referred to our center for excision with MMS. Immediately prior to performing MMS, OCT was used to map the borders of the lesion. MMS then proceeded according to standard protocol. OCT images were compared to histopathology for agreement. Hi...

The Future of High-Speed Digitization with ADQ35

April 16, 2024 | General Technology, Other News | Teledyne SP Devices

Nicklas Gilbertsson

Our team has engineered an advanced upgrade of our Direct Memory Access (DMA) engine, achieving a transfer speed that is twice as fast as current fourth-generation digitizer products. Considering system configuration options, one could efficiently integrate dual ADQ35 units with a single GPU to reach transfer rates of roughly 28 Gbyte/s within a single system. In the perform tests, we used two ADQ35 digitizers to stream data to a single GPU as well as two GPUs respectively. Notably, the cost of the (PC) system remains under $2000, not including the GPU. This performance is facilitated through the use of a x16 PCIe Gen3 link. The tests were performed both on Linux (topmost figure below) and Windows (bottom figure) operating systems. When streaming to a single GPU from both digitizers, the achieved aggregate transfer rate approached 28 Gbyte/s, as indicated by the blue traces in the figure below. Upon incorporating a second GPU, the corresponding aggregate data rate increased to...

Megahertz multi-parametric ophthalmic OCT system for whole eye imaging

April 15, 2024 | General Technology, Ophthalmology | Beijing Union University, Peking University

Dongye Zheng, Gangjun Liu, Qiushi Ren, Xing Long, Yanye Lu, Yicheng Hu, Yutao Feng, Zhiyu Huang

An ultrahigh-speed, wide-field OCT system for the imaging of anterior, posterior, and ocular biometers is crucial for obtaining comprehensive ocular parameters and quantifying ocular pathology size. Here, we demonstrate a multi-parametric ophthalmic OCT system with a speed of up to 1 MHz for wide-field imaging of the retina and 50 kHz for anterior chamber and ocular biometric measurement. A spectrum correction algorithm is proposed to ensure the accurate pairing of adjacent A-lines and elevate the A-scan speed from 500 kHz to 1 MHz for retinal imaging. A registration method employing position feedback signals was introduced, reducing pixel offsets between forward and reverse galvanometer scanning by 2.3 times. Experimental validation on glass sheets and the human eye confirms feasibility and efficacy. Meanwhile, we propose a revised formula to determine the “true” fundus size using all-axial length parameters from different fields of view. The efficient algorithms and compact design...