Journal of the Korean Society for Nondestructive Testing (비파괴검사학회지)

The Korean Society for Nondestructive Testing (한국비파괴검사학회)
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Signal-Characteristic Analysis with Respect to Backing Material of PVDF-Based High-Frequency Ultrasound for Photoacoustic Microscopy

광음향 현미경을 위한 PVDF 기반 고주파수 초음파 변환기의 흡음층 소재에 따른 신호 특성 분석

  • Lee, Junsu ;
  • Chang, Jin Ho (Sogang Institute of Advanced Technolgy/Interdisciplinary Program of Integrated Biotechnolgy/Department of Electronic Engineering, Sogang University)
  • 이준수 (서강대학교 전자공학과) ;
  • 장진호 (서강대학교 서강미래기술연구원, 바이오융합 및 전자공학과)
  • Received : 2014.12.30
  • Accepted : 2015.03.03
  • Published : 2015.04.30
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Abstract

Photoacoustic microscopy is capable of providing high-resolution molecular images, and its spatial resolution is typically determined by ultrasonic transducers used to receive the photoacoustic signals. Therefore, ultrasonic transducers for photoacoustic microscopy (PAM) should have a high operating frequency, broad bandwidth, and high signal-reception efficiency. Polyvinylidene fluoride (PVDF) is a suitable material. To take full advantage of this material, the selection of the backing material is crucial, as it influences the center frequency and bandwidth of the transducer. Therefore, we experimentally determined the most suitable backing material among EPO-TEK 301, E-Solder 3022, and RTV. For this, three PVDF high-frequency single-element transducers were fabricated with each backing material. The center frequency and -6 dB bandwidth of each transducer were ascertained by a pulse-echo test. The spatial resolution of each transducer was examined using wire-target images. The experimental results indicated that EPO-TEK 301 is the most suitable backing material for a PAM transducer. This material provides the highest signal magnitude and a reasonable bandwidth because a large portion of the energy propagates toward the front medium, and the PVDF resonates in the half-wave mode.

고해상도 분자 영상이 가능한 광음향 현미경의 공간해상도는 초음파 변환기에 의해 결정되기 때문에 높은 동작 주파수, 광대역, 높은 신호 수신 효율을 갖는 광음향 수신 변환기는 고성능 광음향 현미경에 필수적이다. Polyvinylidene fluoride (PVDF)는 이러한 광음향 수신 변환기 성능 확보가 가능한 압전소재이다. 그러나 PVDF는 낮은 음향 임피던스로 인해 사용되는 흡음층에 의해서 중심주파수 및 대역폭이 영향을 받게된다. 본 논문에서는 광음향 현미경에 적합한 PVDF 기반 고주파수 초음파 수신 변환기의 최적 흡음층 소재의 음향 임피던스가 최종 변환기 성능에 어떠한 영향을 주는지에 관한 연구를 수행하였다. 이를 위해 EPO-TEK 301, E-Solder 3022, RTV를 각각 흡음층 물질로 사용하여 고주파수 초음파 수신 변환기를 제작하고 그 음향 특성을 평가하였다. 제작된 변환기의 공간해상도를 평가하기 위해 $25{\mu}m$ 직경을 갖는 철심을 표적으로 사용하여 영상을 획득하였으며, 실험을 통해 얻은 펄스-에코 신호 크기 및 중심주파수, -6 dB 대역폭, 공간해상도 평가를 통해 PVDF의 음향 임피던스보다 약간 높은 음향 임피던스를 갖는 EPO-TEK 301이 가장 적합한 흡음층 물질임을 알 수 있었다.

Keywords

References

  1. W. A. Smith and B. A. Auld, "Modeling 1-3 composite piezoelectric: Thickness-mode oscillations," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 38, pp. 40-47 (1991) https://doi.org/10.1109/58.67833
  2. K. K. Shung, "Diagnostic ultrasound: imaging and blood flow measurements," Taylor and Francis, FL, USA, p. 42 (2005)
  3. D. A. Knapik, B. Starkoski, C. J. Pavlin and F. S. Foster, "A 100-200 MHz ultrasound biomicroscope," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 47, pp. 1540-1549 (2000) https://doi.org/10.1109/58.883543
  4. K. A. Snook, J. -Z. Zhao, C. H. F. Alves, J. M. Cannata, W. -H. Chen, R. J. Meyer, T. A. Ritter and K. K. Shung, "Design, fabrication, and evaluation of high frequency, single-element transducers incorporating different materials," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 49, pp. 169-176 (2002) https://doi.org/10.1109/58.985701
  5. J. M. Cannata, T. A. Ritter, W. -H. Chen, R. H. Silverman and K. K. Shung, "Design of efficient, broadband single-element (20-80 MHz) ultrasound transducers for medical imaging applications," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 50, pp. 1548-1557 (2003) https://doi.org/10.1109/TUFFC.2003.1251138
  6. J. Lee, J. H. Chang, J. S. Jeong, C. Lee, S. -Y. Teh, A. Lee and K. K. Shung, "Backscattering measurement from a single microdroplet," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 58, pp. 874-879 (2011) https://doi.org/10.1109/TUFFC.2011.1882
  7. J. S. Jeong and K. K. Shung, "Improved fabrication of focused single element P(VDFTrFE) transducer for high frequency ultrasound applications," Ultrasonics, Vol. 53, pp. 455-458 (2013) https://doi.org/10.1016/j.ultras.2012.08.013
  8. K. B. Kim, B. G. Kim and S. S. Lee, "Development and characterization of high frequency ultrasonic transducer using PVDF and P(VDF_TrFE)," Journal of the Korean Society for Nondestructive Testing, Vol. 22, No. 1, pp. 1-8 (2002)
  9. C. A. Bennett and Jr. R. R. Patty, "Thermal wave interferometry: a potential application of the photoacoustic effect," Applied Optics Letters, Vol. 21, pp. 49-54 (1982) https://doi.org/10.1364/AO.21.000049
  10. L. V. Wang, "Multiscale photoacoustic microscopy and computed tomography," Nature Photonics, Vol. 3, pp. 503-509 (2009) https://doi.org/10.1038/nphoton.2009.157
  11. J. Kang, E. -K. Kim, J. Y. Kwak, Y. Yoo, T. -K. Song and J. H. Chang, "Optimal laser wavelength for photoacoustic imaging of breast microcalcifications," Applied Physics Letter, Vol. 99, pp. 153702 (2011) https://doi.org/10.1063/1.3651333
  12. L. V. Wang and S. Hu, "Photoacoustic tomography: In vivo imaging from organelles to organs," Science, Vol. 335, pp. 1458-1462 (2012) https://doi.org/10.1126/science.1216210
  13. C. Yoon, J. Kang, S. Han, Y. Yoo, T. -K. Song and J. H. Chang, "Enhancement of photoacoustic image quality by sound speed correction: ex vivo evaluation," Optics Express, Vol. 20, pp. 3082-3090 (2012) https://doi.org/10.1364/OE.20.003082
  14. J. S. Lee and J. H. Chang, "Fabrication and evaluation of high frequency ultrasound receive transducers for intravascular photoacoustic imaging," The Journal of the Acoustic Society of Korea, Vol. 33, pp. 300-308 (2014) https://doi.org/10.7776/ASK.2014.33.5.300
  15. H. F. Zhang, K. Maslov, G. Stoica and L. V. Wang, "Functional photoacoustic microscopy for high-resolution and noninvasive in vivo imaging," Nat. Biotechnol., Vol. 24, pp. 848-851 (2006) https://doi.org/10.1038/nbt1220
  16. Piezotech Inc., http://www.piezotech.fr/imge/docments/22-31-32-33-piezotech-piezoelectric-films-leaflet.pdf
  17. H. Wang, T. Ritter, W. Cao and K. K. Shung, "High frequency properties of passive materials for ultrasonic transducers," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 48, pp. 78-84 (2001) https://doi.org/10.1109/58.895911
  18. PZFLEX Program Ver 3.0, Generate Materials File-Rubber
  19. G. R. Lockwood, D. H. Turnbull and F. S. Foster, "Fabrication of high frequency spherically shaped ceramic transducers," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 41, pp. 213-235 (1994)
  20. F. S. Foster, K. A. Harasiewicz and M. D. Sherar, "A History of medical and biological imaging with polyvinylidene fluoride (PVDF) transducers," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, Vol. 47, pp. 1363-1371 (2000) https://doi.org/10.1109/58.883525
  21. F. S. Foster, C. J. Pavlin, K. A. Harasiewicz, D. A. Christopher and D. H. Turnbull, "Advances in ultrasound biomicroscopy," Ultrasound in Med. & Biol., Vol. 26, No. 1. pp. 1-27 (2000) https://doi.org/10.1016/S0301-5629(99)00096-4