Projects

Multimodal remote photoacoustic and OCT imaging

Project information

  • Funding: FWF (P 25584-N20)
  • Volume: EUR 273.000,-
  • Principal investigator: Thomas Berer
  • Co-investigators: Armin Hochreiner, Elisabeth Leiss-Holzinger
  • Duration: April, 1st 2013 – March 31th, 2017

Short description

The project deals with a combination of remote photoacoustic imaging and optical coherence tomography, allowing remote imaging in both modalities. In particular, both imaging modalities are realized with fiber-optic technology within the same fiber optical network.

Figure 1. Simplified schematic of the combined setup

Introduction

Optical coherence tomography (OCT) is a high-resolution and contactless imaging method, which allows depth resolved imaging of refractive image changes in turbid media.  This technique has been originally developed for ophthalmology, and is currently worldwide intensively pursued for further medical diagnostics of biological tissues. Due to its remote nature, OCT allows remote imaging of refractive index changes, thus making it ideal as an inter-operative imaging tool or for inline material inspection.

In contrast to OCT, where changes in the refractive image are measured, photoacoustic imaging (PAI) measures the optical absorption. Imaging relies on the photoacoustic effect, which describes conversion between light and acoustic waves due to absorption of electromagnetic waves and localized thermal expansion. In practice, short laser pulses are used to illuminate a sample. The local absorption of the light is followed by rapid heating, which subsequently leads to thermal expansion and the generation of broadband acoustic waves. By recording the generated ultrasonic waves the initial absorbed energy distribution can be assessed.

Therefore, OCT and PAI deliver complementary information. However, conventional ultrasonic transducers which are used for PAI require physical contact to the specimen. This is a limitation for many applications. This limitation can be overcome by remote photoacoustic imaging (rPAI) techniques, which were recently introduced. Hereby, the acoustic waves are recorded directly on the surface of a specimen by means of interferometry.

Aim

The aim of the proposed project is to demonstrate a combination of rPAI with OCT, thus allowing remote imaging in both modalities. Both imaging techniques, rPAI and OCT, will be realized with fiber-optical components within the same fiber optical network. This allows a relatively simple and robust instrument while providing perfect co-registration of both modalities. For rPAI a low-power optical source is used. Light which is reflected from the surface is amplified by means of optical amplification before detection and demodulation. Due to the combination of a low power optical source and optical amplification before detection, the thermal stresses on the sample can be kept low, while the system provides high spatial resolution.

Results

Results for the PAI part are shown in Fig. 2. The sample consisted of a silicone tube filled with black ink which was formed to a knot. The tube had an inner and outer diameter of 300 µm and 600 µm, respectively. The knot was immersed in a tank filled with a milk/water emulsion. As detection surface an adhesive tape was put on the water surface to mimic smooth skin. A sketch of the phantom is depicted in Fig. 4(d). For generation of ultrasonic waves pulses from the OPO with a radiant exposure of 105 Jm-2 at a wavelength of 740 nm were used. The ultrasonic waves were acquired on the adhesive tape on 71×61 points covering an area of 7×6 mm2. Data acquisition was done without averaging.

Figure 2. (a)-(c) Maximum intensity projections of a silicone loop filled with ink along the z-, x-, and y-direction, respectively. (d) Schematic of the Phantom. A. Hochreiner et al., “Non-contact photoacoustic imaging using a fiber based interferometer with optical amplification,” Biomed. Opt. Express 4(11) , 2013; doi: 10.1364/BOE.4.002322

A significantly reduced data set of the measurement shown in Fig 2, was basis for developing a new compressed sensing reconstruction algorithm for PA imaging [4]

A measurement performed with the final multimodal system is shown in Fig. 3. A phantom was prepared by embedding a skeleton leaf stained with ink into agarose (1 g agarose per 50 mL water). PA signals were generated with the OPO at a wavelength of 710 nm and a radiant exposure of 5??mJ /cm²; the power of the ncPAI interrogation beam on the sample surface was 5 mW. Figure 3 (a) shows the MIP of the photoacoustic reconstruction, (b) MIP of the OCT measurement, (c) the overlay as a perfect match between the two modalities. Fig. 3 (d) shows the volume rendering of OCT data (leaf in red and agarose surface in cyan) and of PAI data (gray).

A significantly reduced data set of the measurement shown in Fig 2, was basis for developing a new compressed sensing reconstruction algorithm for PA imaging [4]. A measurement performed with the final multimodal system is shown in Fig. 3. A phantom was prepared by embedding a skeleton leaf stained with ink into agarose (1 g agarose per 50 mL water). PA signals were generated with the OPO at a wavelength of 710 nm and a radiant exposure of 5??mJ /cm²; the power of the ncPAI interrogation beam on the sample surface was 5 mW. Figure 3 (a) shows the MIP of the photoacoustic reconstruction, (b) MIP of the OCT measurement, (c) the overlay as a perfect match between the two modalities. Fig. 3 (d) shows the volume rendering of OCT data (leaf in red and agarose surface in cyan) and of PAI data (gray). (Paper) Figure 3. ncPAI and OCT measurement of a skeleton leaf/agarose phantom. a) MIP of the photoacoustic reconstruction. b) MIP of the OCT measurement. c) The overlay of OCT and PAI measurement shows perfect matching. d) Volume rendering of OCT data (leaf in red and agarose surface in cyan) and of PAI data (gray). Only half of the volume rendered PAI data are presented for illustrative reasons.

In the frame of this project, additionally non-contact mid-infrared photoacoustic spectroscopy could be realized by generating photoacoustic signals using a tunable quantum cascade laser [2, 9]. Spectral information was obtained for polystyrene and hemoglobin.

Figure 4. (a) Spectrum of hemoglobin obtained by FTIR. (b) Spectrum of polystyrene measured with ATR. (c) Non-contact photoacoustic spectroscopy data of hemoglobin. (d) ncPAS of polystyrene. E. Leiss-Holzinger et al., “Multimodal non-contact photoacoustic imaging and optical coherence tomography using all optical detection,” Proc. SPIE 10057, 100570I (2017); doi: 10.1117/12.2250863.

Publication record

  1. A. Hochreiner, J. Bauer-Marschallinger, P. Burgholzer, B. Jakoby, and T. Berer, “Non-contact photoacoustic imaging using a fiber based interferometer with optical amplification,” Biomed. Opt. Express 4(11), 2322-2331 (2013); doi: 10.1364/BOE.4.002322, https://www.osapublishing.org/boe/abstract.cfm?uri=boe-4-11-2322

  2. T. Berer, E. Leiss-Holzinger, A. Hochreiner, J. Bauer-Marschallinger, A. Buchsbaum, “Multimodal non-contact photoacoustic and optical coherence tomography imaging using wavelength-division multiplexing,” J. Biomed. Opt., 20(4), 046013 (2015); doi:10.1117/1.JBO.20.4.046013, web: .spiedigitallibrary.org/article.aspx?articleid=2288797

  3. Thomas Berer, Markus Brandstetter, Armin Hochreiner, Gregor Langer, Wolfgang Märzinger, Peter Burgholzer, and Bernhard Lendl, “Remote mid-infrared photoacoustic spectroscopy with a quantum cascade laser,” Opt. Letters, 40(15), 3476-3479 (2015); doi: 10.1364/OL.40.003476, https://www.osapublishing.org/ol/abstract.cfm?uri=ol-40-15-3476

  4. E. Leiss-Holzinger, J. Bauer-Marschallinger, A. Hochreiner, P. Hollinger, and T. Berer, “Dual modality non-contact photoacoustic and spectral domain OCT imaging,” Ultrasonic Imaging 38(1), 19-31, 2016; doi: 10.1177/0161734615582003, http://journals.sagepub.com/doi/abs/10.1177/0161734615582003

  5. M. Haltmeier, T. Berer, S. Moon, P. Burgholzer “Compressed sensing and sparsity in photoacoustic tomography,” J. Opt. 18(11), 114004 (2016); doi:10.1088/2040-8978/18/11/114004, web: http://iopscience.iop.org/article/10.1088/2040-8978/18/11/114004

  6. P. Burgholzer, T.W. Murray, M. Haltmeier, E. Leiss-Holzinger, T. Berer, „Photoacoustic super-resolution microscopy using blind structured speckle illumination,” Proc. SPIE 10064, 100642H (2017); doi: 10.1117/12.2250939

  7. T. Berer, E. Leiss-Holzinger, A. Hochreiner, J. Bauer-Marschallinger, M. Leitner, and A. Buchsbaum, “Multimodal non-contact photoacoustic and OCT imaging using a fiber based approach,” Proc. SPIE 8943, 894345 (2014); doi:10.1117/12.2038962
    http://biomedicaloptics.spiedigitallibrary.org/article.aspx?articleid=2288797%20

  8. A. Hochreiner, J. Bauer-Marschallinger, P. Burgholzer, and T. Berer, “Fiber-based remote photoacoustic imaging utilizing a Mach Zehnder interferometer with optical amplification”, Proc. SPIE 8943, 89436B (2014); doi:10.1117/12.2039019

  9. T. Berer, A. Hochreiner, E. Leiss-Holzinger, J. Bauer-Marschallinger, A. Buchsbaum, “Multimodal non-contact photoacoustic and OCT imaging with galvanometer scanning”, Proc. SPIE 9323, 93233T (2015); doi:10.1117/12.2077202

  10. E. Leiss-Holzinger, M. Brandstetter, G. Langer, A. Buchsbaum, P. Burgholzer, B. Lendl, T. Berer, “Multimodal system for non-contact photoacoustic imaging, optical coherence tomography, and mid-infrared photoacoustic spectroscopy,” Proc. SPIE 9708, 970810 (2016); doi: 10.1117/12.2212411

  11. E. Leiss-Holzinger, J. Bauer-Marschallinger, T. Berer, “Multimodal non-contact photoacoustic imaging and optical coherence tomography using all optical detection,” Proc. SPIE 10057, 100570I (2017); doi: 10.1117/12.2250863
    http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2504700

  12. T. Berer, P. Burgholzer, M. Haltmeier, „Compressed sensing in photoacoustic imaging and application for planar detection geometries,” Proc. SPIE 10064, 100642I (2017); doi: 10.1117/12.2250857

  13. P. Burgholzer, T.W. Murray, M. Haltmeier, E. Leiss-Holzinger, T. Berer, „Photoacoustic super-resolution microscopy using blind structured speckle illumination,” Proc. SPIE 10064, 100642H (2017); doi: 10.1117/12.2250939

Go back