Bio

Bio


Dr. Liu has over 10 years educational and research experience in Biomedical imaging and is the author of over 20 peer-reviewed scientific publications and conference papers. Her Ph.D. and early postdoctoral trainings were focused on the development of near-infrared spectroscopy (NIRS) and its application to breast cancer detection, including both human and small animal models. Since summer 2011, she has been working as a postdoctoral scholar in the Center for Interdisciplinary Brain Sciences Research (CIBSR) at Stanford University. Dr. Liu?s current research focus on the following projects: development of neurofeedback-based intervention paradigms to enhance cognitive functions of children with autism spectrum disorder (ASD); investigation of neuroimaging as a biomarker for children with ASD; development of functional NIRS as a stand alone technique and in combination with functional MRI for cognitive studies.

Honors & Awards


  • Translational Postdoctoral Fellowship, Autism Speaks (9/1/2013 -8/31/2015)

Professional Education


  • Doctor of Philosophy, Tufts University (2009)

Stanford Advisors


Research & Scholarship

Current Research and Scholarly Interests


Development of neurofeedback-based intervention paradigms to enhance cognitive functions of children with autism spectrum disorder (ASD); investigation of neuroimaging as a biomarker for children with ASD; development of functional NIRS as a stand alone technique and in combination with functional MRI for cognitive studies.

Projects


  • Imaging-based real-time feedback to enhance therapeutic intervention in ASD, Autism speaks Inc. (9/1/2013 - 8/31/2015)

    Functional near infrared spectroscopy (fNIRS) is a new, state-of-the-art neuroimaging method. It is safe, portable, easy to use, patient-friendly and cost-effective. fNIRS allows measurement of brain function in a naturalistic environment (e.g., sitting and conversing) and can be used to provide real-time monitoring of dynamic brain activity. Autism spectrum disorder (ASD) is the most compelling among all brain-based disorders with respect to impact on the life of the affected individual, and the wide variation in symptoms and severity. Since there is currently no cure for autism, a focus on the development of new, more effective therapeutic interventions could significantly improve the quality of life for those with ASD. This project will develop a highly novel fNIRS-based paradigm to enhance the effectiveness of behavioral interventions focused on social cognition. Specifically, the investigators will utilize fNIRS to enable clinicians to quantitatively determine brain activation of their patients in real-time, and provide feedback to their patients based on neural circuitry as well as behavioral response. This project will accelerate the translation of fNIRS functional imaging to enhance the treatment of ASD. The initial stage of the research training will provide fundamental knowledge of ASD including diagnostic procedures, evidence-based clinical interventions and prevailing theories of contributory neurobiology. The fellowship experience will also provide training in fNIRS signal processing and analysis within a bioengineering context. The collective training has the potential to lead to translational biomedical imaging, and to develop more effective methods and devices to treat ASD.

    Location

    401 Quarry Rd. Stanford, CA

Publications

Journal Articles


  • Near-infrared spectral imaging of the female breast for quantitative oximetry in optical mammography APPLIED OPTICS Yu, Y., Liu, N., Sassaroli, A., Fantini, S. 2009; 48 (10): D225-D235

    Abstract

    We present a hybrid continuous-wave, frequency-domain instrument for near-infrared spectral imaging of the female breast based on a tandem, planar scanning of one illumination optical fiber and one collection optical fiber configured in a transmission geometry. The spatial sampling rate of 25 points/cm(2) is increased to 400 points/cm(2) by postprocessing the data with a 2D cubic spline interpolation. We then apply a previously developed spatial second-derivative algorithm to an edge-corrected intensity image (N-image) to enhance the visibility and resolution of optical inhomogeneities in breast tissue such as blood vessels and tumors. The spectral data at each image pixel consist of 515-point spectra over the 650-900 nm wavelength range, thus featuring a spectral density of two data points per nanometer. We process the measured spectra with a paired-wavelength spectral analysis method to quantify the oxygen saturation of detected optical inhomogeneities, under the assumption that they feature a locally higher hemoglobin concentration. Our initial measurements on two healthy human subjects have generated high-resolution optical mammograms displaying a network of blood vessels with values of hemoglobin saturation typically falling within the 60%-95% range, which is physiologically reasonable. This approach to spectral imaging and oximetry of the breast has the potential to efficiently exploit the high intrinsic contrast provided by hemoglobin in breast tissue and to contribute a useful tool in the detection, diagnosis, and monitoring of breast pathologies.

    View details for Web of Science ID 000265443700027

    View details for PubMedID 19340113

  • Paired-wavelength spectral approach to measuring the relative concentrations of two localized chromophores in turbid media: an experimental study JOURNAL OF BIOMEDICAL OPTICS Liu, N., Sassaroli, A., Fantini, S. 2007; 12 (5)

    Abstract

    We present an experimental test of a new spectral approach that is aimed at quantifying the relative concentrations of two chromophores that are contained in a defect embedded in a turbid medium. The basic steps of our spectral approach are (a) perform a linear tandem scan of the source and detector across the defect; (b) measure the spectral dependence of the maximum change induced by the defect in the scanned intensity; (c) identify a set of appropriate pairs of wavelengths (lambda1, lambda2) at which such maximum intensity changes are the same; and (d) measure the reduced scattering coefficient spectrum of the background medium. For each wavelength pair (lambda1, lambda2), we obtain a measurement of the relative concentrations of the two chromophores, where the only required parameters are the extinction coefficients of the two chromophores and the ratio of the background scattering coefficients at lambda1 and lambda2. In a mixture of two test chromophores (blue food coloring dye and black India ink) contained in a 0.78-cm diameter cylinder, our spectral approach yielded relative concentrations values that were within 6% of their actual values. Although our paired-wavelength spectral approach is not generally applicable to any pair of chromophores, it is suitable for oxyhemoglobin and deoxyhemoglobin and is thus appropriate for oximetry of localized lesions in biological tissues.

    View details for DOI 10.1117/1.2779349

    View details for Web of Science ID 000251549600014

    View details for PubMedID 17994871

  • Spatial and spectral information in optical mammography TECHNOLOGY IN CANCER RESEARCH & TREATMENT Fantini, S., Heffer, E. L., Pera, V. E., Sassaroli, A., Liu, N. 2005; 4 (5): 471-482

    Abstract

    This article reviews our research activities in the area of optical mammography and relates them to the historical developments and the current state and trends in the field. The guiding threads for this article are the roles played in optical mammography by spatial and spectral information. The first feature, spatial information, is limited by the diffusive nature of light propagation but can take advantage of the exceptionally high optical contrast featured by blood vessels and blood-rich areas in the breast. We describe a method to correct for edge effects, a spatial second-derivative algorithm, and a two-dimensional phased-array approach that enhance the image contrast, the spatial resolution, and the depth discrimination in optical mammograms. The second feature, spectral information, is the most powerful and unique capability of optical mammography, and allows for functional measurements associated with hemoglobin concentration and oxygenation, water concentration, lipids content, and the wavelength dependence of tissue scattering. We present oxygenation-index images obtained from multi-wavelength optical data that point to the diagnostic potential of oxygenation information in optical mammography. The optimization of the spatial and spectral information in optical mammography has the potential to create a role for this imaging modality in the detection and monitoring of breast cancer.

    View details for Web of Science ID 000232572900003

    View details for PubMedID 16173819

  • Two-dimensional phased arrays of sources and detectors for depth discrimination in diffuse optical imaging JOURNAL OF BIOMEDICAL OPTICS Liu, N., Sassaroli, A., Fantini, S. 2005; 10 (5)

    Abstract

    We present a multisource, multidetector phased-array approach to diffuse optical imaging that is based on postprocessing continuous-wave data. We previously showed that this approach enhances the spatial resolution of diffuse optical imaging. We now demonstrate the depth discrimination capabilities of this approach and its potential to perform tomographic sectioning of turbid media. The depth discrimination results from the dependence of the sensitivity function on the depth coordinate z. To demonstrate the potential of this approach, we perform an experimental study of a turbid medium containing cylindrical inhomogeneities that are placed 2.0, 3.0, and 4.0 cm from a seven-element, 2-D source array. A single detector element is placed at a distance of 6.0 cm from the source array, and the measurement is repeated after switching the positions of the detector and the source array to simulate the case where both sources and detectors consist of a 2-D array of elements. We find that the proposed phased-array method is able to separate cylinders at different depths, thus showing cross-sectioning capabilities.

    View details for DOI 10.1117/1.2085172

    View details for Web of Science ID 000233711300024

    View details for PubMedID 16292959

  • Three-element phased-array approach to diffuse optical imaging based on postprocessing of continuous-wave data OPTICS LETTERS Liu, N., Sassaroli, A., Zucker, M. A., Fantini, S. 2005; 30 (3): 281-283

    Abstract

    We present a multielement phased-array approach to diffuse optical imaging based on postprocessing of continuous-wave data for the improvement of spatial resolution. In particular, we present a theoretical and experimental analysis of the performance of a three-element source array in the study of an optically turbid medium with two embedded cylindrical inclusions. We find that the proposed phased-array approach is able to resolve two cylinders with side-to-side separation of 10 mm that are not resolved by the intensity associated with a single light source.

    View details for Web of Science ID 000226678300021

    View details for PubMedID 15751885

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