Dr. Ali M. Fard Profile

Dr. Ali M. Fard

at ZEISS

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Publications (3)

Proceedings Article | 27 April 2016 Presentation

Compensation of spectral artifacts in dual-modality intravascular optical coherence tomography and near-infrared spectroscopy (Conference Presentation)

Ali Fard, Joseph Gardecki, Giovanni Ughi, Chulho Hyun, Guillermo Tearney

Proceedings Volume 9689, 96892Z (2016) https://doi.org/10.1117/12.2219948

KEYWORDS: Near infrared spectroscopy, Optical coherence tomography, Light sources, Arteries, 3D image processing, In vivo imaging, Imaging technologies, Reliability, Data acquisition, Spectral calibration

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Intravascular optical coherence tomography (OCT) is a high-resolution catheter-based imaging method that provides three-dimensional microscopic images of coronary artery in vivo, facilitating coronary artery disease treatment decisions based on detailed morphology. Near-infrared spectroscopy (NIRS) has proven to be a powerful tool for identification of lipid-rich plaques inside the coronary walls. We have recently demonstrated a dual-modality intravascular imaging technology that integrates OCT and NIRS into one imaging catheter using a two-fiber arrangement and a custom-made dual-channel fiber rotary junction. It therefore enables simultaneous acquisition of microstructural and composition information at 100 frames/second for improved diagnosis of coronary lesions. The dual-modality OCT-NIRS system employs a single wavelength-swept light source for both OCT and NIRS modalities. It subsequently uses a high-speed photoreceiver to detect the NIRS spectrum in the time domain. Although use of one light source greatly simplifies the system configuration, such light source exhibits pulse-to-pulse wavelength and intensity variation due to mechanical scanning of the wavelength. This can be in particular problematic for NIRS modality and sacrifices the reliability of the acquired spectra. In order to address this challenge, here we developed a robust data acquisition and processing method that compensates for the spectral variations of the wavelength-swept light source. The proposed method extracts the properties of the light source, i.e., variation period and amplitude from a reference spectrum and subsequently calibrates the NIRS datasets. We have applied this method on datasets obtained from cadaver human coronary arteries using a polygon-scanning (1230-1350nm) OCT system, operating at 100,000 sweeps per second. The results suggest that our algorithm accurately and robustly compensates the spectral variations and visualizes the dual-modality OCT-NIRS images. These findings are therefore crucial for the practical application and clinical translation of dual-modality intravascular OCT-NIRS imaging when the same swept sources are used for both OCT and spectroscopy.

Proceedings Article | 15 March 2013 Paper

3D ultrafast laser scanner

A. Mahjoubfar, K. Goda, C. Wang, A. Fard, J. Adam, D. Gossett, A. Ayazi, E. Sollier, O. Malik, E. Chen, Y. Liu, R. Brown, N. Sarkhosh, D. Di Carlo, B. Jalali

Proceedings Volume 8611, 86110N (2013) https://doi.org/10.1117/12.2003135

KEYWORDS: Laser scanners, 3D scanning, Prisms, Mirrors, Blood, Raster graphics, Pulsed laser operation, Biomedical optics, Vibrometry, Ultrafast lasers

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Proceedings Article | 22 February 2013 Paper

Real-time image processor for detection of rare cells and particles in flow at 37 MHz line scans per second

A. Ayazi, K. Goda, J. Sadasivam, C. Lonappan, D. Gossett, Elodie Sollier, A. Fard, S. C. Hur, S. H. Kim, J. Adam, C. Murray, C. Wang, N. Brackbill, D. Di Carlo, Bahram Jalali

Proceedings Volume 8587, 858713 (2013) https://doi.org/10.1117/12.2002709

KEYWORDS: Image processing, Particles, Blood, Statistical analysis, Yeast, Cameras, Field programmable gate arrays, Camera shutters, Metals, Microfluidics

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