Shaozhen Song | University of Washington (original) (raw)

Papers by Shaozhen Song

Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVIII, 2014

ABSTRACT Optical coherence tomography (OCT) provides high spatial resolution and sensitivity that... more ABSTRACT Optical coherence tomography (OCT) provides high spatial resolution and sensitivity that are ideal for imaging the cornea and lens. Quantifying the biomechanical properties of these tissues could add clinically valuable information. Thus, we propose a dynamic elastography method combining OCT detection and a mechanical actuator to map the shear modulus of soft tissues. We used a piezoelectric actuator driven in the kHz range and we used phase-sensitive OCT (PhS-OCT) to track the resulting shear waves at an equivalent frame rate of 47 kHz. We mapped the shear wave speed of anesthetized mice cornea using monochromatic excitations. We found a significant difference between a group of knock-out (3.92 +/- 0.35 m/s, N=4) and wild-type mice (5.04 +/- 0.51 m/s, N=3). These preliminary results demonstrate the feasibility of using PhS-OCT to perform in vivo shear wave elastography of the cornea. We then implemented a shear pulse compression approach on ex vivo human cornea. For that purpose, frequency- modulated excitations were used and the resulting displacement field was digitally compressed in a short broadband pulse with a 7 dB gain in signal-to-noise ratio (SNR).

2013 IEEE International Ultrasonics Symposium (IUS), 2013

ABSTRACT In this paper, we introduced the combined acoustical and optical method for imaging the ... more ABSTRACT In this paper, we introduced the combined acoustical and optical method for imaging the propagating shear waves and mapping the shear modulus with a high resolution that is comparable to optical coherence tomography (OCT). The mechanical waves propagation is dynamically imaged with phase-sensitive OCT (PhS-OCT) with an equivalent frame rate of ~47 kHz. The 2-D elastography image is retrieved from measuring the shear wave velocity in the imaging region. The quantitative accuracy of this method is examined by validating experiments on agar phantoms.

With the benefits of high accuracy and non-invasive implementation, high intensity focused ultras... more With the benefits of high accuracy and non-invasive implementation, high intensity focused ultrasound (HIFU) is a promising medical procedure to heat and destroy pathogenic tissue rapidly. However, the relation between the power emitted by the ultrasound transducer and the energy arriving at the target area is complex, interfered by several factors such as the properties of tissue, obstacles of hard tissues or vascularization. In this study, a finite element model was used to simulate the propagation process of focused ultrasound inside tissue phantom and passing the perfused vascular. Then, the resultant sound pressure distribution provided the heat source for heat transfer process simulation. The simulation results were validated with thermocouple measurements in egg white phantoms. This study demonstrated an efficient methodology for estimating the thermal effects in HIFU hyperthermia therapy, especially in the region with large blood vessel. This study will be useful in minimizing difficulties and risks in HIFU induced hyperthermia treatment and facilitate the extension from laboratory to clinic use.

Optical Elastography and Tissue Biomechanics II, 2015

Journal of biomedical optics, 2013

We propose an integrated method combining low-frequency mechanics with optical imaging to map the... more We propose an integrated method combining low-frequency mechanics with optical imaging to map the shear modulus within the biological tissue. Induced shear wave propagating in tissue is tracked in space and time using phase-sensitive optical coherence tomography (PhS-OCT). Local estimates of the shear-wave speed obtained from tracking results can image the local shear modulus. A PhS-OCT system remotely records depth-resolved, dynamic mechanical waves at an equivalent frame rate of ∼47 kHz with the high spatial resolution. The proposed method was validated by examining tissue-mimicking phantoms made of agar and light scattering material. Results demonstrate that the shear wave imaging can accurately map the elastic moduli of these phantoms.

Optical Elastography and Tissue Biomechanics II, 2015

The purpose of this study is to implement a beam-steering ultrasound as the wave source for shear... more The purpose of this study is to implement a beam-steering ultrasound as the wave source for shear-wave optical coherence elastography (SW-OCE) to achieve an extended range of elastic imaging of the tissue sample. We introduce a linear phased array ultrasound transducer (LPAUT) as the remote and programmable wave source and a phase-sensitive optical coherence tomography (OCT) as the sensitive shear-wave detector. The LPAUT is programmed to launch acoustic radiation force impulses (ARFI) focused at desired locations within the range of OCT imaging, upon which the elasticity map of the entire OCT B-scan cross section is recovered by spatial compounding of the elastic maps derived from each launch of AFRIs. We also propose a directional filter to separate the shear-wave propagation at different directions in order to reduce the effect of tissue heterogeneity on the shear-wave propagation within tissue. The feasibility of this proposed approach is then demonstrated by determining the stiffness of tissue-mimicking phantoms with agarose concentrations of 0.5% and 1% and also by imaging the Young's modulus of retinal and choroidal tissues within a porcine eye ball ex vivo. The approach opens up opportunities to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative assessment of tissue biomechanical property.

Journal of Biomedical Optics, 2015

Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the unders... more Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6). © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Cancer letters, 2015

We present first quantitative three-dimensional (3D) data sets recorded using optical coherence e... more We present first quantitative three-dimensional (3D) data sets recorded using optical coherence elastography (OCE) for the diagnosis and detection of prostate cancer (PCa). 120 transrectal ultrasound guided prostate biopsy specimens from 10 men suspected with prostate cancer were imaged using OCE. 3D quantitative mechanical assessment of biopsy specimens obtained in kilopascals (kPa) at an interval of 40 µm was compared with histopathology. Sensitivity, specificity, and positive and negative predictive values were calculated for OCE in comparison to histopathology. The results show OCE imaging could reliably differentiate between benign prostate tissue, acinar atypical hyperplasia, prostatic intraepithelial neoplasia and malignant PCa. The sensitivity and specificity of OCE for the detection of prostate cancer was 0.98 and 0.91 with AUC > 0.99. Quantitative 3D OCE based on the assessment of mechanical properties of tissues can reliably differentiate prostate tissue specimen in an...

ABSTRACT Shear wave elastography measures the stiffness of soft tissues from the speed of propaga... more ABSTRACT Shear wave elastography measures the stiffness of soft tissues from the speed of propagating shear waves induced in tissue. Optical coherence tomography (OCT) is a promising detection modality given its high sensitivity and spatial resolution, making it suitable for elastic characterization of skin, peripheral vasculature or ocular tissues. For clinical applications, it would be valuable to use a non-contact shear source. Thus, we propose acoustic radiation force as a remote shear source combined with OCT for visualization. A single-element focused transducer (central frequency 7.5 MHz) was used to apply a maximal pressure of ~3 MPa for 100 μs in agar phantoms. It induced shear waves with an amplitude of several hundreds of nanometers and a broadband spectrum in the kilohertz range. Phasesensitive OCT was used to track shear waves at an equivalent frame rate of 47 kHz. We reconstructed shear modulus maps in a heterogeneous phantom. In addition, we use 3-ms long coded excitation to increase the displacement signal-to-noise ratio. We applied digital pulse compression to the resulting displacement field to obtain a gain of ~15 dB compared to standard pulse excitation while maintaining the US pressure level and the shear wave spatial and temporal resolution. This is a promising result for shear wave generation at low US pressures (~ 1 MPa).

2014 IEEE International Ultrasonics Symposium, 2014

Ultrasonics, 2013

Advances in the field of laser ultrasonics have opened up new possibilities in applications in ma... more Advances in the field of laser ultrasonics have opened up new possibilities in applications in many areas. This paper verifies the relationship between phase velocities of different materials, including hard solid and soft solid, and the frequency range of SAW signal. We propose a novel approach that utilizes a low coherence interferometer to detect the laser-induced surface acoustic waves (SAWs). A Nd:YAG focused laser line-source is applied to steel, iron, plastic plates and a 3.5% agar-agar phantom. The generated SAW signals are detected by a time domain low coherence interferometry system. SAW phase velocity dispersion curves were calculated, from which the elasticity of the specimens was evaluated. The relationship between frequency content and phase velocities was analyzed. We show that the experimental results agreed well with those of the theoretical expectations.

Optics Letters, 2014

We report on the use of phase-sensitive optical coherence tomography (PhS-OCT) to detect and trac... more We report on the use of phase-sensitive optical coherence tomography (PhS-OCT) to detect and track temporal and spatial shear wave propagation within tissue, induced by ultrasound radiation force. Kilohertz-range shear waves are remotely generated in samples using focused ultrasound emission and their propagation is tracked using PhS-OCT. Cross-sectional maps of the local shear modulus are reconstructed from local estimates of shear wave speed in tissue-mimicking phantoms. We demonstrate the feasibility of combining ultrasound radiation force and PhS-OCT to perform high-resolution mapping of the shear modulus.

Journal of Biomedical Optics, 2014

Assessing the biomechanical properties of soft tissue provides clinically valuable information to... more Assessing the biomechanical properties of soft tissue provides clinically valuable information to supplement conventional structural imaging. In the previous studies, we introduced a dynamic elastography technique based on phase-sensitive optical coherence tomography (PhS-OCT) to characterize submillimetric structures such as skin layers or ocular tissues. Here, we propose to implement a pulse compression technique for shear wave elastography. We performed shear wave pulse compression in tissue-mimicking phantoms. Using a mechanical actuator to generate broadband frequency-modulated vibrations (1 to 5 kHz), induced displacements were detected at an equivalent frame rate of 47 kHz using a PhS-OCT. The recorded signal was digitally compressed to a broadband pulse. Stiffness maps were then reconstructed from spatially localized estimates of the local shear wave speed. We demonstrate that a simple pulse compression scheme can increase shear wave detection signal-to-noise ratio (>12 dB gain) and reduce artifacts in reconstructing stiffness maps of heterogeneous media. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Journal of Biomedical Optics, 2013

We describe theoretical and experimental investigations of motion artifacts that can arise in the... more We describe theoretical and experimental investigations of motion artifacts that can arise in the detection of shear wave propagating within tissue with phase-sensitive optical coherence tomography. We find that the motion artifact is a combined product of sample surface motion and refractive index difference between sample and air, which cannot be neglected when estimating the tissue motion within tissue. A method of compensating the motion artifact is demonstrated, the results of which emphasize the need for surface motion compensation when measuring the mechanical response for elastography or other biomedical applications.

Biomedical optics express, 2014

The maintenance of urinary bladder elasticity is essential to its functions, including the storag... more The maintenance of urinary bladder elasticity is essential to its functions, including the storage and voiding phases of the micturition cycle. The bladder stiffness can be changed by various pathophysiological conditions. Quantitative measurement of bladder elasticity is an essential step toward understanding various urinary bladder disease processes and improving patient care. As a nondestructive, and noncontact method, laser-induced surface acoustic waves (SAWs) can accurately characterize the elastic properties of different layers of organs such as the urinary bladder. This initial investigation evaluates the feasibility of a noncontact, all-optical method of generating and measuring the elasticity of the urinary bladder. Quantitative elasticity measurements of ex vivo porcine urinary bladder were made using the laser-induced SAW technique. A pulsed laser was used to excite SAWs that propagated on the bladder wall surface. A dedicated phase-sensitive optical coherence tomography...

Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVIII, 2014

ABSTRACT Optical coherence tomography (OCT) provides high spatial resolution and sensitivity that... more ABSTRACT Optical coherence tomography (OCT) provides high spatial resolution and sensitivity that are ideal for imaging the cornea and lens. Quantifying the biomechanical properties of these tissues could add clinically valuable information. Thus, we propose a dynamic elastography method combining OCT detection and a mechanical actuator to map the shear modulus of soft tissues. We used a piezoelectric actuator driven in the kHz range and we used phase-sensitive OCT (PhS-OCT) to track the resulting shear waves at an equivalent frame rate of 47 kHz. We mapped the shear wave speed of anesthetized mice cornea using monochromatic excitations. We found a significant difference between a group of knock-out (3.92 +/- 0.35 m/s, N=4) and wild-type mice (5.04 +/- 0.51 m/s, N=3). These preliminary results demonstrate the feasibility of using PhS-OCT to perform in vivo shear wave elastography of the cornea. We then implemented a shear pulse compression approach on ex vivo human cornea. For that purpose, frequency- modulated excitations were used and the resulting displacement field was digitally compressed in a short broadband pulse with a 7 dB gain in signal-to-noise ratio (SNR).

2013 IEEE International Ultrasonics Symposium (IUS), 2013

ABSTRACT In this paper, we introduced the combined acoustical and optical method for imaging the ... more ABSTRACT In this paper, we introduced the combined acoustical and optical method for imaging the propagating shear waves and mapping the shear modulus with a high resolution that is comparable to optical coherence tomography (OCT). The mechanical waves propagation is dynamically imaged with phase-sensitive OCT (PhS-OCT) with an equivalent frame rate of ~47 kHz. The 2-D elastography image is retrieved from measuring the shear wave velocity in the imaging region. The quantitative accuracy of this method is examined by validating experiments on agar phantoms.

With the benefits of high accuracy and non-invasive implementation, high intensity focused ultras... more With the benefits of high accuracy and non-invasive implementation, high intensity focused ultrasound (HIFU) is a promising medical procedure to heat and destroy pathogenic tissue rapidly. However, the relation between the power emitted by the ultrasound transducer and the energy arriving at the target area is complex, interfered by several factors such as the properties of tissue, obstacles of hard tissues or vascularization. In this study, a finite element model was used to simulate the propagation process of focused ultrasound inside tissue phantom and passing the perfused vascular. Then, the resultant sound pressure distribution provided the heat source for heat transfer process simulation. The simulation results were validated with thermocouple measurements in egg white phantoms. This study demonstrated an efficient methodology for estimating the thermal effects in HIFU hyperthermia therapy, especially in the region with large blood vessel. This study will be useful in minimizing difficulties and risks in HIFU induced hyperthermia treatment and facilitate the extension from laboratory to clinic use.

Optical Elastography and Tissue Biomechanics II, 2015

Journal of biomedical optics, 2013

We propose an integrated method combining low-frequency mechanics with optical imaging to map the... more We propose an integrated method combining low-frequency mechanics with optical imaging to map the shear modulus within the biological tissue. Induced shear wave propagating in tissue is tracked in space and time using phase-sensitive optical coherence tomography (PhS-OCT). Local estimates of the shear-wave speed obtained from tracking results can image the local shear modulus. A PhS-OCT system remotely records depth-resolved, dynamic mechanical waves at an equivalent frame rate of ∼47 kHz with the high spatial resolution. The proposed method was validated by examining tissue-mimicking phantoms made of agar and light scattering material. Results demonstrate that the shear wave imaging can accurately map the elastic moduli of these phantoms.

Optical Elastography and Tissue Biomechanics II, 2015

The purpose of this study is to implement a beam-steering ultrasound as the wave source for shear... more The purpose of this study is to implement a beam-steering ultrasound as the wave source for shear-wave optical coherence elastography (SW-OCE) to achieve an extended range of elastic imaging of the tissue sample. We introduce a linear phased array ultrasound transducer (LPAUT) as the remote and programmable wave source and a phase-sensitive optical coherence tomography (OCT) as the sensitive shear-wave detector. The LPAUT is programmed to launch acoustic radiation force impulses (ARFI) focused at desired locations within the range of OCT imaging, upon which the elasticity map of the entire OCT B-scan cross section is recovered by spatial compounding of the elastic maps derived from each launch of AFRIs. We also propose a directional filter to separate the shear-wave propagation at different directions in order to reduce the effect of tissue heterogeneity on the shear-wave propagation within tissue. The feasibility of this proposed approach is then demonstrated by determining the stiffness of tissue-mimicking phantoms with agarose concentrations of 0.5% and 1% and also by imaging the Young&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s modulus of retinal and choroidal tissues within a porcine eye ball ex vivo. The approach opens up opportunities to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative assessment of tissue biomechanical property.

Journal of Biomedical Optics, 2015

Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the unders... more Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6). © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Cancer letters, 2015

We present first quantitative three-dimensional (3D) data sets recorded using optical coherence e... more We present first quantitative three-dimensional (3D) data sets recorded using optical coherence elastography (OCE) for the diagnosis and detection of prostate cancer (PCa). 120 transrectal ultrasound guided prostate biopsy specimens from 10 men suspected with prostate cancer were imaged using OCE. 3D quantitative mechanical assessment of biopsy specimens obtained in kilopascals (kPa) at an interval of 40 µm was compared with histopathology. Sensitivity, specificity, and positive and negative predictive values were calculated for OCE in comparison to histopathology. The results show OCE imaging could reliably differentiate between benign prostate tissue, acinar atypical hyperplasia, prostatic intraepithelial neoplasia and malignant PCa. The sensitivity and specificity of OCE for the detection of prostate cancer was 0.98 and 0.91 with AUC > 0.99. Quantitative 3D OCE based on the assessment of mechanical properties of tissues can reliably differentiate prostate tissue specimen in an...

ABSTRACT Shear wave elastography measures the stiffness of soft tissues from the speed of propaga... more ABSTRACT Shear wave elastography measures the stiffness of soft tissues from the speed of propagating shear waves induced in tissue. Optical coherence tomography (OCT) is a promising detection modality given its high sensitivity and spatial resolution, making it suitable for elastic characterization of skin, peripheral vasculature or ocular tissues. For clinical applications, it would be valuable to use a non-contact shear source. Thus, we propose acoustic radiation force as a remote shear source combined with OCT for visualization. A single-element focused transducer (central frequency 7.5 MHz) was used to apply a maximal pressure of ~3 MPa for 100 μs in agar phantoms. It induced shear waves with an amplitude of several hundreds of nanometers and a broadband spectrum in the kilohertz range. Phasesensitive OCT was used to track shear waves at an equivalent frame rate of 47 kHz. We reconstructed shear modulus maps in a heterogeneous phantom. In addition, we use 3-ms long coded excitation to increase the displacement signal-to-noise ratio. We applied digital pulse compression to the resulting displacement field to obtain a gain of ~15 dB compared to standard pulse excitation while maintaining the US pressure level and the shear wave spatial and temporal resolution. This is a promising result for shear wave generation at low US pressures (~ 1 MPa).

2014 IEEE International Ultrasonics Symposium, 2014

Ultrasonics, 2013

Advances in the field of laser ultrasonics have opened up new possibilities in applications in ma... more Advances in the field of laser ultrasonics have opened up new possibilities in applications in many areas. This paper verifies the relationship between phase velocities of different materials, including hard solid and soft solid, and the frequency range of SAW signal. We propose a novel approach that utilizes a low coherence interferometer to detect the laser-induced surface acoustic waves (SAWs). A Nd:YAG focused laser line-source is applied to steel, iron, plastic plates and a 3.5% agar-agar phantom. The generated SAW signals are detected by a time domain low coherence interferometry system. SAW phase velocity dispersion curves were calculated, from which the elasticity of the specimens was evaluated. The relationship between frequency content and phase velocities was analyzed. We show that the experimental results agreed well with those of the theoretical expectations.

Optics Letters, 2014

We report on the use of phase-sensitive optical coherence tomography (PhS-OCT) to detect and trac... more We report on the use of phase-sensitive optical coherence tomography (PhS-OCT) to detect and track temporal and spatial shear wave propagation within tissue, induced by ultrasound radiation force. Kilohertz-range shear waves are remotely generated in samples using focused ultrasound emission and their propagation is tracked using PhS-OCT. Cross-sectional maps of the local shear modulus are reconstructed from local estimates of shear wave speed in tissue-mimicking phantoms. We demonstrate the feasibility of combining ultrasound radiation force and PhS-OCT to perform high-resolution mapping of the shear modulus.

Journal of Biomedical Optics, 2014

Assessing the biomechanical properties of soft tissue provides clinically valuable information to... more Assessing the biomechanical properties of soft tissue provides clinically valuable information to supplement conventional structural imaging. In the previous studies, we introduced a dynamic elastography technique based on phase-sensitive optical coherence tomography (PhS-OCT) to characterize submillimetric structures such as skin layers or ocular tissues. Here, we propose to implement a pulse compression technique for shear wave elastography. We performed shear wave pulse compression in tissue-mimicking phantoms. Using a mechanical actuator to generate broadband frequency-modulated vibrations (1 to 5 kHz), induced displacements were detected at an equivalent frame rate of 47 kHz using a PhS-OCT. The recorded signal was digitally compressed to a broadband pulse. Stiffness maps were then reconstructed from spatially localized estimates of the local shear wave speed. We demonstrate that a simple pulse compression scheme can increase shear wave detection signal-to-noise ratio (>12 dB gain) and reduce artifacts in reconstructing stiffness maps of heterogeneous media. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Journal of Biomedical Optics, 2013

We describe theoretical and experimental investigations of motion artifacts that can arise in the... more We describe theoretical and experimental investigations of motion artifacts that can arise in the detection of shear wave propagating within tissue with phase-sensitive optical coherence tomography. We find that the motion artifact is a combined product of sample surface motion and refractive index difference between sample and air, which cannot be neglected when estimating the tissue motion within tissue. A method of compensating the motion artifact is demonstrated, the results of which emphasize the need for surface motion compensation when measuring the mechanical response for elastography or other biomedical applications.

Biomedical optics express, 2014

The maintenance of urinary bladder elasticity is essential to its functions, including the storag... more The maintenance of urinary bladder elasticity is essential to its functions, including the storage and voiding phases of the micturition cycle. The bladder stiffness can be changed by various pathophysiological conditions. Quantitative measurement of bladder elasticity is an essential step toward understanding various urinary bladder disease processes and improving patient care. As a nondestructive, and noncontact method, laser-induced surface acoustic waves (SAWs) can accurately characterize the elastic properties of different layers of organs such as the urinary bladder. This initial investigation evaluates the feasibility of a noncontact, all-optical method of generating and measuring the elasticity of the urinary bladder. Quantitative elasticity measurements of ex vivo porcine urinary bladder were made using the laser-induced SAW technique. A pulsed laser was used to excite SAWs that propagated on the bladder wall surface. A dedicated phase-sensitive optical coherence tomography...