Linear frequency modulation photoacoustic radar: Optimal bandwidth and signal-to-noise ratio for frequency-domain imaging of turbid media

Lashkari, Bahman; Mandelis, Andreas

doi:10.1121/1.3605290

Cited by 41 publications

(50 citation statements)

References 34 publications

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“…large beam size) has been shown to approximate the 1D solution 18 as illustrated in Figure 2 assuming uniform irradiation using a Gaussian laser beam intensity profile, and ignoring the effect of absorption through the cylinder. …”

Section: Wm-dpa Imaging Of Uniformly Radiated Long Cylindermentioning

confidence: 97%

Wavelength-Modulated Differential Photoacoustic (WM-DPA) imaging: a high dynamic range modality towards noninvasive diagnosis of cancer

et al. 2016

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This study explores wavelength-modulated differential photoacoustic (WM-DPA) imaging for non-invasive early cancer detection via sensitive characterization of functional information such as hemoglobin oxygenation (sO 2 ) levels. Wellknown benchmarks of tumor formation such as angiogenesis and hypoxia can be addressed this way. While most conventional photoacoustic imaging has almost entirely employed high-power pulsed lasers, frequency-domain photoacoustic radar (FD-PAR) has seen significant development as an alternative technique. It employs a continuous wave laser source intensity-modulated and driven by frequency-swept waveforms. WM-DPA imaging utilizes chirp modulated laser beams at two distinct wavelengths for which absorption differences between oxy-and deoxygenated hemoglobin are minimum (isosbestic point, 805 nm) and maximum (680 nm) to simultaneously generate two signals detected using a standard commercial array transducer as well as a single-element transducer that scans the sample. Signal processing is performed using Lab View and Matlab software developed in-house.Minute changes in total hemoglobin concentration (tHb) and oxygenation levels are detectable using this method since background absorption is suppressed due to the out-of-phase modulation of the laser sources while the difference between the two signals is amplified, thus allowing pre-malignant tumors to become identifiable. By regulating the signal amplitude ratio and phase shift the system can be tuned to applications like cancer screening, sO 2 quantification and hypoxia monitoring in stroke patients. Experimental results presented demonstrate WM-DPA imaging of sheep blood phantoms in comparison to single-wavelength FD-PAR imaging. Future work includes the functional PA imaging of small animals in vivo.

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Section: Wm-dpa Imaging Of Uniformly Radiated Long Cylindermentioning

confidence: 97%

Wavelength-Modulated Differential Photoacoustic (WM-DPA) imaging: a high dynamic range modality towards noninvasive diagnosis of cancer

et al. 2016

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“…These parameters can be optimized based on transducer transfer function (TTF) and other system considerations to provide the maximum SNR [23], [24]. In an ideal system, the response to (1) is its replica.…”

Section: Design Of Weakly Correlated (Mismatched) Waveformsmentioning

confidence: 99%

High-Frame-Rate Synthetic Aperture Ultrasound Imaging Using Mismatched Coded Excitation Waveform Engineering: A Feasibility Study

Lashkari

Zhang

Mandelis

2016

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Mismatched coded excitation (CE) can be employed to increase the frame rate of synthetic aperture ultrasound imaging. The high autocorrelation and low cross correlation (CC) of transmitted signals enables the identification and separation of signal sources at the receiver. Thus, the method provides B-mode imaging with simultaneous transmission from several elements and capability of spatial decoding of the transmitted signals, which makes the imaging process equivalent to consecutive transmissions. Each transmission generates its own image and the combination of all the images results in an image with a high lateral resolution. In this paper, we introduce two different methods for generating multiple mismatched CEs with an identical frequency bandwidth and code length. Therefore, the proposed families of mismatched CEs are able to generate similar resolutions and signal-to-noise ratios. The application of these methods is demonstrated experimentally. Furthermore, several techniques are suggested that can be used to reduce the CC between the mismatched codes.

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“…Linear frequency modulation chirps and a matched filtering method were employed to generate A-scans. 21 The chirp duration was 1 ms and A-scans were generated by averaging over 180 to 300 signal detections. The chirp bandwidth was adjusted according to the employed transducer and desired resolution.…”

Section: The Combined Pa and Us Experimental Set-upmentioning

confidence: 99%

Combined photoacoustic and ultrasonic diagnosis of early bone loss and density variations

Lashkari

Mandelis

2012

SPIE Proceedings

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Over the past two decades, osteoporosis has been recognized among the most serious public health problems. Fortunately with the growing awareness of osteoporosis, new treatments have been developed for the prevention of fracture. At the same time, there is a rapid improvement in diagnostic methods. In this study biomedical photoacoustics (PA) is applied to the analysis of bone mineral concentration. The PA signal depends on optical as well as mechanical properties of the object and therefore has the potential to provide higher sensitivity to density variations compared with standard diagnostic methods, like ultrasound. A laser source with 800 nm wavelength and different ultrasonic transducers with resonance frequencies in the range 1 to 5 MHz were employed. The CW or frequency-domain (FD) PA radar method was utilized with linear frequency modulation chirps to provide temporal gating control over the transmitted signal and higher sensitivity in the detected signal. The laser intensity was set below the safety standards for skin exposure. The preliminary studies showed adequate optical absorption by cortical bone to generate measurable PA signals and the transmission of laser light through this layer. Experiments are focused on detection and evaluation of PA signals from in-vitro animal cortical bones with and without a trabecular sublayer. The trabecular layer is then diluted by chemical etching and differences in the PA signals are discussed.

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Linear frequency modulation photoacoustic radar: Optimal bandwidth and signal-to-noise ratio for frequency-domain imaging of turbid media

Cited by 41 publications

References 34 publications

Wavelength-Modulated Differential Photoacoustic (WM-DPA) imaging: a high dynamic range modality towards noninvasive diagnosis of cancer

Wavelength-Modulated Differential Photoacoustic (WM-DPA) imaging: a high dynamic range modality towards noninvasive diagnosis of cancer

High-Frame-Rate Synthetic Aperture Ultrasound Imaging Using Mismatched Coded Excitation Waveform Engineering: A Feasibility Study

Combined photoacoustic and ultrasonic diagnosis of early bone loss and density variations

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