Abstract

Transparent ultrasound transducers could enable many novel applications involving both ultrasonics and optics. Recently, we reported transparent capacitive micromachined ultrasound transducers (CMUTs) and demonstrated through-illumination photoacoustic imaging. This work presents the feasibility of transparent CMUTs for combined ultrasound imaging and through-array white-light imaging with a miniature camera placed behind the array. Transparent CMUT devices are fabricated with an adhesive wafer bonding technique and provide high transparency up to 90% in visible wavelengths. Fabricated linear arrays have a central operating frequency of 9 MHz with 128 active elements. Realtime plane-wave imaging is performed for ultrasound imaging, and lateral and axial resolutions of, respectively, 234 and 338 µm are achieved. Transparent CMUT has demonstrated a high transmit sensitivity of 1.4 kPa/V per channel with a 100 VDC bias voltage. The signal-to-noise ratio for a beamformed image of wire targets is determined to be 28.4 dB. To the best of our knowledge, this is the first report of combined realtime optical and ultrasonic imaging with transparent arrays. This technology may enable one to visually see what is being scanned and scan what one sees without co-registration errors. Future applications could include multi-modality probes for interventional and surgical procedures.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Most ultrasound transducers are opaque, limiting their combined use with important optical methods. Transparent ultrasound transducers could enable emerging novel technologies. For example, transparent arrays could enable exact co-registration of optical- and ultrasonic imaging, enable through-illumination photoacoustic imaging, and may have novel applications to non-medical technologies such as smart ultrasonic touchscreens and biometrics such as transparent ultrasonic fingerprint scanners. Here we develop transparent ultrasound linear arrays for combined ultrasound- and white-light camera imaging with the objective of optical visualization of the scanning targets that are depth-imaged with ultrasound. One motivating application for this technology is multi-modality endoscopy. Endoscopy makes it possible to inspect and diagnose the gastrointestinal tract [1] and is a tool for interventional and surgical procedures. Superficial visualization is a limitation of camera endoscopy, making it hard, and sometimes impossible, to detect deeper disorders. To address this, endoscopic ultrasound imaging technology can be used to reveal depth-related information beyond the surface [2]. This includes visualization of lungs, gal bladder, pancreas, and liver without the need for surgical exposure [3,4]. High-frequency endoscopic ultrasound may also enable assessment of depth of invasion in gastrointestinal malignancies. However, gastro-enterologists and surgeons currently have endoscopic ultrasound technologies that are poorly co-registered with optical endoscopy [57]. Improved co-registration between optical and ultrasonic imaging methods could lead to reduced procedure times, miniaturized probes, more confident navigation and more accurate diagnosis. Such improved co-registration could be achieved with transparent ultrasound transducers. However, development of transparent transducers is non-trivial.

Transparent piezoelectric transducers were recently fabricated with lithium niobate [8]. These transducers provided high transparency in the visible wavelength range; however, the investigators developed only single element transducers, not arrays. Difficulty achieving transparent backing and matching materials is another drawback of these transducers, resulting in unwanted ringing and poor transmission efficiency due to acoustic impedance mismatches. On the other hand, transparent capacitive micromachined ultrasound transducers (CMUTs) require no such layers and can be made highly transparent. Optical-based ultrasound transducers such as Fabry–Perot etalons [9,10] can be made transparent, and while they possess high receive sensitivity, they require long optical readouts, need non-transparent layers to achieve ultrasonic excitation, and cannot achieve steerable ultrasound transmit focusing. CMUTs have also been shown to exhibit exquisite receive sensitivity, albeit with only modest transmit sensitivity. Previous works on transparent CMUTs include NIR-transparent CMUTs by Zhang et al. [11] and Chen et al. [12]. However, these provided poor visible-light transparency due to the use of silicon layers in the CMUT structure. Our group previously introduced highly transparent immersible CMUTs in the visible wavelength spectrum for the first time. Li et al. [2] first introduced such transparent CMUTs by fabricating single element transducers using transparent silicon nitride membranes, transparent indium–tin–oxide (ITO) electrodes, and a transparent adhesive bonding agent. We further improved the fabrication and introduced transparent linear arrays for photoacoustic imaging applications [13]. Here we introduce transparent CMUT linear arrays for combined ultrasound and white-light optical imaging using a miniature camera embedded behind the array. One of the potential challenges in achieving high ultrasound image quality with such transparent CMUTs could be acoustic reverberations in the glass substrate. Another challenge is to achieve sufficient optical transparency when using a large number of wired elements, since thin-strip ITO electrical conductivity is poor and requires augmenting the conductivity with metal strips. Finally, acoustic transmit and receive performances of such devices must be validated.

Transparent CMUT arrays were fabricated using an adhesive wafer bonding process and transparent electrode and membrane materials, similar to our previous work. In brief, a 200 nm ITO layer was deposited on fused-silica wafers (JGS2) using a DC magnetron sputtering process (at 6 mTorr, 200°C substrate temperature, 50 sccm of Ar, with 75 W, 6 µs pulse duration, and 150 KHz repetition frequency). After annealing at 250°C for 30 min, we reached $15\;\Omega /{\rm sq}$ resistivity while also achieving high optical transparency ($\gt\!{98}\%$). CMUT gap structures are formed into spin-coated benzocyclobutene (BCB) (380 nm thickness) layers using photolithography. An adhesion layer was spin-coated onto an low-pressure chemical vapor deposition (LPCVD) nitride-coated prime wafer prior to bonding to the BCB-patterned fused-silica wafer using 500 KPa pressure and 250°C temperature with a chamber pressure of 5 mTorr for 1 h (SUSS Bonder ELAN-CB6L). The prime-wafer silicon handle was etched away in a KOH solution to release the SiN membranes. Top transparent ITO electrodes were deposited using the same procedure described above for bottom electrodes. Photolithography was used to pattern the ITO into thin strips defining individual transducer elements with hydrochloric acid (HCL) wet-etching (room temperature for 26 s), using SiN as an etch-stop. To improve the conductivity of top electrodes along their length, we formed thin-metal strips (2 µm width), which had a minimal overall impact on transparency, but improved conductivity from $\gt\!1\;{\rm M}\Omega$ to $\sim\!56\;\Omega$ over a 7 mm length. This was achieved by chrome–copper–gold evaporation with thicknesses of 10 nm, 1 µm, and 50 nm, respectively. Fabricated CMUTs had 17.75 µm radius membranes of 1 µm thickness. Optical transparency was similar to our previous work, with peak transmission >90%. The device cross-section with a photo of a fabricated CMUT die is shown in Fig. 1. With this fabrication process, we developed 64- and 128-element lambda-pitch linear arrays targeting 7.5 MHz center frequency.

 figure: Fig. 1.

Fig. 1. (Left) Cross-sectional drawing of the CMUT structure. (Right) Photo of transparent CMUT over University of Alberta logo demonstrating the device transparency.

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Figure 2 shows a diagram of our ultrasound combined ultrasound–optical imaging system. Optical imaging is performed with a small $6 \times 6\;{\rm mm}$ color charge-coupled device (CCD) camera. The camera has a 5 MP resolution, and with the help of a high-speed driver board, the camera can captures high-resolution videos at 60 frames per second. Ultrasound imaging is performed with a 128-element transparent CMUT array. An application-specific printed circuit board (PCB) is designed to connect our programmable ultrasound system to the CMUT die. Each element of the transducer is connected to a bias-tee to bias the CMUT and transmit or receive the ultrasound signal.

 figure: Fig. 2.

Fig. 2. Diagram of our combined ultrasound-optical imaging system using transparent linear array CMUT transducers.

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For biasing the CMUT elements, we developed a high-voltage H-bridge metal–oxide–semiconductor field-effect transistor (MOSFET) configuration that provides sub-microsecond switching time and bi-polar biasing up to $\pm250\;{\rm VDC}$ on each channel, independently. Fast switching is useful for bias encoded imaging schemes, which can provide opportunities for future high-quality 2D/3D imaging [14]. Ultrasound transmit–receive signals are recorded with a 256-channel Verasonics Vantage research ultrasound system. CMUT elements are operated with a central transmit frequency of 9 MHz. To minimize parasitic capacitance and improve the signal-to-noise (SNR) ratio of the received ultrasound signal, for each channel, a voltage-protected low-noise pre-amplifier (MAX4805A) is placed in the path between the CMUT and the ultrasound system. The breakout PCB board has an opening under the CMUT die for positioning the camera behind the transparent CMUT device. An acrylic tank is glued on the PCB and filled with vegetable oil to mimic the tissue. A wire phantom is suspended above the die as an imaging target. Figure 3(a) illustrates the cross-sectional view of the setup, and Figs. 3(b) and 3(c) present a side view and a top view of the die and the camera, respectively.

 figure: Fig. 3.

Fig. 3. Ultrasound transparent array evaluation setup. (a) Cross-sectional view of the setup, (b) side photo of the setup illustrating the phantom wire targets and the ultrasound sensor, and (c) top view of the setup, showing the camera position under the CMUT die.

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Plane-wave ultrasound imaging is performed with 100 VDC bias voltage and $30\;{V_{{\rm pp}}}$ transmit signal amplitude. After receiving the ultrasound signal, a CPU delay-and-sum beamforming technique [15,16] is used to generate the beamformed images. Figures 4(a) and 4(b) illustrate the optical and ultrasound images of the wire phantom. Video capture of the moving phantom wire and realtime ultrasound beamforming is provided in Supplement 1. Due to computational limitations, the ultrasound display is rendered with 47 frames per second. To demonstrate the ability of the array for ultrasound imaging of tissues, we imaged an ex vivo rat heart with an inserted needle. A photo of the experimental setup, along with optical and ultrasound images, is shown in Fig. 5. The needle location is apparent as the bright spot in the ultrasound image.

 figure: Fig. 4.

Fig. 4. Combined optical–ultrasound imaging test results. (a) Camera shot of the wire phantom through transducer and (b) beamformed image of the wire phantom targets with 10 mm spacing. For ultrasound imaging, plain-wave imaging is performed with a bias voltage of 100 VDC on all elements, and transmit signal amplitude is set to $30\;{V_{{\rm pp}}}$. A full-length video recording of realtime optical–ultrasound imaging is provided in Visualization 1.

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 figure: Fig. 5.

Fig. 5. (a) Photo of ex vivo experimental setup, (b) camera image of tissue with needle, and (c) ultrasound image using the transparent CMUT array.

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Optical imaging through transparent CMUT may experience optical distortion and reduced image quality. To determine the image distortion caused by the CMUT, a USAF 1951 target is imaged. Two optical images are taken before and after installing the CMUT in front of the camera. Figures 6(a) and 6(b) present the photos, respectively. A negligible image distortion is recorded by comparing the results where the camera’s resolution remained the same for both photos at 12.70 lp/mm (line pairs per millimeter).

 figure: Fig. 6.

Fig. 6. Optical and ultrasound characterization of the setup. (a) Camera resolution test with USAF 1951 target without attaching the transparent CMUT. (b) Camera resolution test through CMUT. (c) Time-varying acoustic pressure generated with a single element of the transparent CMUT due to a transmit pulse with 100 µJ energy under various bias voltages. (d) Frequency response of the transmit sensitivity. The central operating frequency is determined to be 9 MHz with a fractional bandwidth of 150%.

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Generating high SNR ultrasound images is highly dependent on transmit and receive sensitivity of the transducer. High-pressure ultrasound waves penetrate deeper in tissue and produce stronger back-reflected ultrasound pressures, resulting in high-quality images. To determine the transducer’s transmit sensitivity, a pulse with 100 µJ energy is applied (Olympus 5900PR Pulser Receiver) to a single element of the transducer, and generated pressure is recorded with a hydrophone (Onda NHP-0400). Without a bias voltage, each element generates ultrasound pressures over 0.2 MPa peak-to-peak, which could be further increased up to 0.8 MPa peak-to-peak with the presence of a 250 VDC bias voltage. Transmit pressure of elements across the array was measured to be similar to representative data shown here for one element, with less than 8% variability between elements. Also, transmitting with all elements and implementing elevational focusing may further improve the transmit sensitivity. The transducer has a central immersion frequency of 9 MHz with a ${-}{6}\;{\rm dB}$ bandwidth of 150%. Figures 6(c) and 6(d) show the transmit test results and frequency response of the transducer, respectively.

Receive sensitivity was quantified by measuring signals recorded due to a hydrophone-calibrated external transducer transmitting pressure transients. The transparent arrays presented a receive sensitivity of $37.5\;{\rm mPa}/\sqrt {{\rm Hz}}$ with a bias voltage of 100 VDC or $10.4\;{\rm mPa}/\sqrt {{\rm Hz}}$ with a bias voltage of 250 VDC. Ultrasound imaging of a 25 µm bonding wire target provided lateral and axial resolutions of 234 µm and 338 µm, respectively. Axial and lateral resolutions were determined from a beamformed image of a gold wire phantom with a 25 µm diameter where a 50% drop in the intensity was observed. Compared to optical imaging (having a resolution of 40 µm or 12.7 lp/mm), ultrasound has a coarser resolution, but provides depth information. An SNR of 28.4 dB was recorded for the received ultrasound signals.

Future work should aim to further improve transmit and receive sensitivity, further improve optical transparency, and explore new applications. Ultrasound image quality can be further improved with the help of temporal codes, more advanced imaging sequences, and aperture encoding [14]. Tri-modality ultrasound–photoacoustic–optical imaging could enable exciting pre-clinical and clinical imaging opportunities [13] since photoacoustic imaging can provide biological and molecular information of the target tissue [17]. Transparent arrays could also enable next-generation neuroscience tools by enabling both optogenetic activation and ultrafast functional brain imaging.

To the best of our knowledge, this is the first time using a transparent transducer for through-array combined optical–ultrasound imaging. Transparent transducers provide unique opportunities over opaque transducers and may enable novel miniaturized multi-modality endoscopic probes by placing a camera behind the transducer. Realtime co-registered optical and ultrasound imaging may open new doors for ultrasound-guided surgeries, and could lead to reduced procedure times, more confident navigation, and more accurate diagnosis. A limitation of our work is the lack of an acoustic lens. Future work could include curved arrays, transparent acoustic lenses, or transparent 2D arrays for improved elevational and 3D imaging.

Funding

Canadian Cancer Society (706275); Canadian Institutes of Health Research (PS 153067); Natural Sciences and Engineering Research Council of Canada (I2IPJ 536752-19, RGPIN-2018-05788, STPGP 494293-16).

Acknowledgment

We are grateful to CMC Microsystems for access to the design tools used in this work.

Disclosures

R. Zemp is a founder and shareholder of illumiSonics Inc. and CliniSonix Inc., which, however, did not support this work.

REFERENCES

1. J. Mannath and K. Ragunath, Nat. Rev. Gastroenterol. Hepatol. 13, 720 (2016). [CrossRef]  

2. Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018). [CrossRef]  

3. J. T. Annema, M. Veseliç, and K. F. Rabe, Lung Cancer 48, 357 (2005). [CrossRef]  

4. P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004). [CrossRef]  

5. S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012). [CrossRef]  

6. J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.

7. J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017). [CrossRef]  

8. A. Dangi, S. Agrawal, and S.-R. Kothapalli, Opt. Lett. 44, 5326 (2019). [CrossRef]  

9. K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

10. P. Hajireza, K. Krause, M. Brett, and R. Zemp, Opt. Express 21, 6391 (2013). [CrossRef]  

11. X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017). [CrossRef]  

12. J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012). [CrossRef]  

13. A. K. Ilkhechi, C. Ceroici, Z. Li, and R. Zemp, Opt. Express 28, 13750 (2020). [CrossRef]  

14. C. Ceroici, K. Latham, R. Chee, B. Greenlay, Q. Barber, J. A. Brown, and R. Zemp, Opt. Lett. 43, 3425 (2018). [CrossRef]  

15. J. Kortbek, J. A. Jensen, and K. L. Gammelmark, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 966–969.

16. S. Park, A. B. Karpiouk, S. R. Aglyamov, and S. Y. Emelianov, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 1088–1091.

17. Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019). [CrossRef]  

References

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  1. J. Mannath and K. Ragunath, Nat. Rev. Gastroenterol. Hepatol. 13, 720 (2016).
    [Crossref]
  2. Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
    [Crossref]
  3. J. T. Annema, M. Veseliç, and K. F. Rabe, Lung Cancer 48, 357 (2005).
    [Crossref]
  4. P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
    [Crossref]
  5. S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
    [Crossref]
  6. J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.
  7. J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
    [Crossref]
  8. A. Dangi, S. Agrawal, and S.-R. Kothapalli, Opt. Lett. 44, 5326 (2019).
    [Crossref]
  9. K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).
  10. P. Hajireza, K. Krause, M. Brett, and R. Zemp, Opt. Express 21, 6391 (2013).
    [Crossref]
  11. X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
    [Crossref]
  12. J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
    [Crossref]
  13. A. K. Ilkhechi, C. Ceroici, Z. Li, and R. Zemp, Opt. Express 28, 13750 (2020).
    [Crossref]
  14. C. Ceroici, K. Latham, R. Chee, B. Greenlay, Q. Barber, J. A. Brown, and R. Zemp, Opt. Lett. 43, 3425 (2018).
    [Crossref]
  15. J. Kortbek, J. A. Jensen, and K. L. Gammelmark, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 966–969.
  16. S. Park, A. B. Karpiouk, S. R. Aglyamov, and S. Y. Emelianov, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 1088–1091.
  17. Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
    [Crossref]

2020 (1)

2019 (2)

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

A. Dangi, S. Agrawal, and S.-R. Kothapalli, Opt. Lett. 44, 5326 (2019).
[Crossref]

2018 (2)

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

C. Ceroici, K. Latham, R. Chee, B. Greenlay, Q. Barber, J. A. Brown, and R. Zemp, Opt. Lett. 43, 3425 (2018).
[Crossref]

2017 (2)

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
[Crossref]

2016 (1)

J. Mannath and K. Ragunath, Nat. Rev. Gastroenterol. Hepatol. 13, 720 (2016).
[Crossref]

2013 (1)

2012 (2)

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
[Crossref]

2005 (1)

J. T. Annema, M. Veseliç, and K. F. Rabe, Lung Cancer 48, 357 (2005).
[Crossref]

2004 (1)

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Adelegan, O. J.

X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
[Crossref]

Aglyamov, S. R.

S. Park, A. B. Karpiouk, S. R. Aglyamov, and S. Y. Emelianov, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 1088–1091.

Agrawal, S.

Annema, J. T.

J. T. Annema, M. Veseliç, and K. F. Rabe, Lung Cancer 48, 357 (2005).
[Crossref]

Barber, Q.

Beard, P.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Brett, M.

Brown, J. A.

Ceroici, C.

Chee, R.

Chen, J.

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

Chen, J. J.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Chen, R.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

Chen, S.

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.

Chen, Z.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Cheng, J.-C.

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

Cheng, X.

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

Cox, B.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Dangi, A.

Desjardins, A.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Emelianov, S. Y.

S. Park, A. B. Karpiouk, S. R. Aglyamov, and S. Y. Emelianov, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 1088–1091.

Gammelmark, K. L.

J. Kortbek, J. A. Jensen, and K. L. Gammelmark, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 966–969.

Greenlay, B.

Hajireza, P.

Hawes, R. H.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

He, Y.

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Heidari, A. E.

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Hoffman, B. J.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Huo, T.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
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Huynh, N.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Ilkhechi, A. K.

Jaros, J.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Jensen, J. A.

J. Kortbek, J. A. Jensen, and K. L. Gammelmark, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 966–969.

Jiang, L.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

Jing, J. C.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Karpiouk, A. B.

S. Park, A. B. Karpiouk, S. R. Aglyamov, and S. Y. Emelianov, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 1088–1091.

King, P.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Kortbek, J.

J. Kortbek, J. A. Jensen, and K. L. Gammelmark, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 966–969.

Kothapalli, S.-R.

Krause, K.

Kuklis, F.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Kushima, R.

S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
[Crossref]

Latham, K.

Li, P.-C.

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

Li, X.

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.

Li, Y.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

Li, Z.

Lu, G.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

Ma, T.

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Mannath, J.

J. Mannath and K. Ragunath, Nat. Rev. Gastroenterol. Hepatol. 13, 720 (2016).
[Crossref]

Noimark, S.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Nonaka, S.

S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
[Crossref]

Oda, I.

S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
[Crossref]

Oralkan, Ö.

X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
[Crossref]

Park, S.

S. Park, A. B. Karpiouk, S. R. Aglyamov, and S. Y. Emelianov, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 1088–1091.

Patel, A.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Peng, J.

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.

Peng, X.

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.

Pham, K.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Prasad, P.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Rabe, K. F.

J. T. Annema, M. Veseliç, and K. F. Rabe, Lung Cancer 48, 357 (2005).
[Crossref]

Ragunath, K.

J. Mannath and K. Ragunath, Nat. Rev. Gastroenterol. Hepatol. 13, 720 (2016).
[Crossref]

Roberts, S.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Saito, Y.

S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
[Crossref]

Schmulewitz, N.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Shung, K. K.

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

Tang, H.

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.

Tutuian, R.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Varadarajulu, S.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Veseliç, M.

J. T. Annema, M. Veseliç, and K. F. Rabe, Lung Cancer 48, 357 (2005).
[Crossref]

Wallace, M. B.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Wang, M.

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

Wang, T.

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

Wang, Y.-H.

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

Wildi, S. M.

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

Wu, X.

X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
[Crossref]

Yamaner, F. Y.

X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
[Crossref]

Yoshinaga, S.

S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
[Crossref]

Yu, M.

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Zemp, R.

Zhang, E.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

Zhang, X.

X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
[Crossref]

Zhou, Q.

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

Zhu, J.

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Zhu, Z.

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

Gastrointest. Endosc. (1)

P. Prasad, N. Schmulewitz, A. Patel, S. Varadarajulu, S. M. Wildi, S. Roberts, R. Tutuian, P. King, R. H. Hawes, B. J. Hoffman, and M. B. Wallace, Gastrointest. Endosc. 59, 49 (2004).
[Crossref]

IEEE J. Sel. Top. Quantum Electron. (1)

Y. Li, Z. Zhu, J. C. Jing, J. J. Chen, A. E. Heidari, Y. He, J. Zhu, T. Ma, M. Yu, Q. Zhou, and Z. Chen, IEEE J. Sel. Top. Quantum Electron. 25, 7102005 (2018).
[Crossref]

IEEE Trans. Biomed. Eng. (1)

J. Peng, X. Peng, H. Tang, X. Li, R. Chen, Y. Li, T. Wang, S. Chen, K. K. Shung, and Q. Zhou, IEEE Trans. Biomed. Eng. 65, 140 (2017).
[Crossref]

IEEE Trans. Ultrason., Ferroelectr., Freq. Control (2)

X. Zhang, X. Wu, O. J. Adelegan, F. Y. Yamaner, and Ö. Oralkan, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 65, 85 (2017).
[Crossref]

J. Chen, M. Wang, J.-C. Cheng, Y.-H. Wang, P.-C. Li, and X. Cheng, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 59, 766 (2012).
[Crossref]

Lung Cancer (1)

J. T. Annema, M. Veseliç, and K. F. Rabe, Lung Cancer 48, 357 (2005).
[Crossref]

Nat. Rev. Gastroenterol. Hepatol. (1)

J. Mannath and K. Ragunath, Nat. Rev. Gastroenterol. Hepatol. 13, 720 (2016).
[Crossref]

Opt. Express (2)

Opt. Lett. (2)

Photoacoustics (1)

Y. Li, G. Lu, J. J. Chen, J. C. Jing, T. Huo, R. Chen, L. Jiang, Q. Zhou, and Z. Chen, Photoacoustics 15, 100138 (2019).
[Crossref]

World J. Gastrointestinal Endosc. (1)

S. Yoshinaga, I. Oda, S. Nonaka, R. Kushima, and Y. Saito, World J. Gastrointestinal Endosc. 4, 218 (2012).
[Crossref]

Other (4)

J. Peng, X. Li, H. Tang, X. Peng, and S. Chen, in IEEE International Ultrasonics Symposium (IUS) (IEEE, 2017), pp. 1–4.

K. Pham, S. Noimark, N. Huynh, E. Zhang, F. Kuklis, J. Jaros, A. Desjardins, B. Cox, and P. Beard, “Broadband all-optical plane-wave ultrasound imaging system based on a Fabry-Perot scanner,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control (to be published).

J. Kortbek, J. A. Jensen, and K. L. Gammelmark, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 966–969.

S. Park, A. B. Karpiouk, S. R. Aglyamov, and S. Y. Emelianov, in IEEE Ultrasonics Symposium (IEEE, 2008), pp. 1088–1091.

Supplementary Material (1)

NameDescription
» Visualization 1       Live combined optical-ultrasound imaging test results.

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Figures (6)

Fig. 1.
Fig. 1. (Left) Cross-sectional drawing of the CMUT structure. (Right) Photo of transparent CMUT over University of Alberta logo demonstrating the device transparency.
Fig. 2.
Fig. 2. Diagram of our combined ultrasound-optical imaging system using transparent linear array CMUT transducers.
Fig. 3.
Fig. 3. Ultrasound transparent array evaluation setup. (a) Cross-sectional view of the setup, (b) side photo of the setup illustrating the phantom wire targets and the ultrasound sensor, and (c) top view of the setup, showing the camera position under the CMUT die.
Fig. 4.
Fig. 4. Combined optical–ultrasound imaging test results. (a) Camera shot of the wire phantom through transducer and (b) beamformed image of the wire phantom targets with 10 mm spacing. For ultrasound imaging, plain-wave imaging is performed with a bias voltage of 100 VDC on all elements, and transmit signal amplitude is set to $30\;{V_{{\rm pp}}}$. A full-length video recording of realtime optical–ultrasound imaging is provided in Visualization 1.
Fig. 5.
Fig. 5. (a) Photo of ex vivo experimental setup, (b) camera image of tissue with needle, and (c) ultrasound image using the transparent CMUT array.
Fig. 6.
Fig. 6. Optical and ultrasound characterization of the setup. (a) Camera resolution test with USAF 1951 target without attaching the transparent CMUT. (b) Camera resolution test through CMUT. (c) Time-varying acoustic pressure generated with a single element of the transparent CMUT due to a transmit pulse with 100 µJ energy under various bias voltages. (d) Frequency response of the transmit sensitivity. The central operating frequency is determined to be 9 MHz with a fractional bandwidth of 150%.