Coded excitation waveform engineering for high frame rate synthetic aperture ultrasound imaging.

Coded excitation was initially introduced to ultrasound imaging as a method for enhancing the signal-to-noise ratio (SNR). However, this method was also shown to be helpful in conjunction with synthetic aperture transmission for high frame rate imaging. Recently, we introduced two families of mismatched coded excitations based on frequency modulation chirp and combined frequency modulation and Golay code.

Quantitative phase-filtered wavelength-modulated differential photoacoustic radar tumor hypoxia imaging toward early cancer detection.

Overcoming the limitations of conventional linear spectroscopy used in multispectral photoacoustic imaging, wherein a linear relationship is assumed between the absorbed optical energy and the absorption spectra of the chromophore at a specific location, is crucial for obtaining accurate spatially-resolved quantitative functional information by exploiting known chromophore-specific spectral characteristics. This study introduces a non-invasive phase-filtered differential photoacoustic technique, wavelength-modulated differential photoacoustic radar (WM-DPAR) imaging that addresses this issue by eliminating the effect of the unknown wavelength-dependent fluence. It employs two laser wavelengths modulated out-of-phase to significantly suppress background absorption while amplifying the difference between the two photoacoustic signals.

Wavelength-modulated differential photoacoustic radar imager (WM-DPARI): accurate monitoring of absolute hemoglobin oxygen saturation.

Accurate monitoring of blood oxy-saturation level (SO2 ) in human breast tissues is clinically important for predicting and evaluating possible tumor growth at the site. In this work, four different non-invasive frequency-domain photoacoustic (PA) imaging modalities were compared for their absolute SO2 characterization capability using an in-vitro sheep blood circulation system. Among different PA modes, a new WM-DPAR imaging modality could estimate the SO2 with great accuracy when compared to a commercial blood gas analyzer.

Building a symbolic computer algebra toolbox to compute 2D Fourier transforms in polar coordinates.

The development of a symbolic computer algebra toolbox for the computation of two dimensional (2D) Fourier transforms in polar coordinates is presented. Multidimensional Fourier transforms are widely used in image processing, tomographic reconstructions and in fact any application that requires a multidimensional convolution. By examining a function in the frequency domain, additional information and insights may be obtained.

Simultaneous dual-wavelength photoacoustic radar imaging using waveform engineering with mismatched frequency modulated excitation.

The spectroscopic imaging capability of photoacoustics (PA) without the depth limitations of optical methods offers a major advantage in preclinical and clinical applications. Consecutive PA measurements with properly chosen wavelengths allow composition related information about blood or tissue. In this work, we propose and experimentally introduce modulation waveform engineering through the use of mismatched (uncorrelated or weakly correlated) linear frequency modulated signals for PA characterization and imaging.

Photoacoustic radar phase-filtered spatial resolution and co-registered ultrasound image enhancement for tumor detection.

Co-registered ultrasound (US) and frequency-domain photoacoustic radar (FD-PAR) imaging is reported for the first time in this paper. The merits of ultrasound and cross-correlation (radar) frequency-domain photoacoustic imaging are leveraged for accurate tumor detection. Commercial US imagers possess sophisticated, optimized software for rapid image acquisition that could dramatically speed-up PA imaging.