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. 2014 Jan 22;2(1):39-46.
doi: 10.1016/j.pacs.2013.12.002. eCollection 2014 Mar.

All-optical scanhead for ultrasound and photoacoustic imaging-Imaging mode switching by dichroic filtering

Bao-Yu Hsieh  1 , Sung-Liang Chen  2 , Tao Ling  2 , L Jay Guo  2 , Pai-Chi Li  3
Affiliations

All-optical scanhead for ultrasound and photoacoustic imaging-Imaging mode switching by dichroic filtering

Bao-Yu Hsieh et al. Photoacoustics. .

Abstract

Ultrasound (US) and photoacoustic (PA) multimodality imaging has the advantage of combining good acoustic resolution with high optical contrast. The use of an all-optical scanhead for both imaging modalities can simplify integration of the two systems and miniaturize the imaging scanhead. Herein we propose and demonstrate an all-optical US/PA scanhead using a thin plate for optoacoustic generation in US imaging, a polymer microring resonator for acoustic detection, and a dichroic filter to switch between the two imaging modes by changing the laser wavelength. A synthetic-aperture focusing technique is used to improve the resolution and contrast. Phantom images demonstrate the feasibility of this design, and show that axial and lateral resolutions of 125 μm and 2.52°, respectively, are possible.

Keywords: All-optical scanhead; Dichroic filtering; Photoacoustic imaging; Ultrasound.

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Figures

Fig. 1
Fig. 1
Schematics showing the mechanisms underlying (a) US and (b) PA imaging.
Fig. 2
Fig. 2
Experimental setup of the US/PA imaging system with the all-optical scanhead design. MMF, multimode fiber; SMF, single-mode fiber.
Fig. 3
Fig. 3
(a) Transmission and (b) optical absorptions of the dichroic filter. The green arrows indicate 532-nm laser light; the red arrows indicate 750-nm laser. I0 and I are the intensity of the incident light and the transmitted light, respectively.
Fig. 4
Fig. 4
Schematic of the signal processing.
Fig. 5
Fig. 5
Configurations of (a) the wire phantom and (b) the cyst-like phantom.
Fig. 6
Fig. 6
(a) Waveform and (b) frequency spectrum of a typical generated US signal.
Fig. 7
Fig. 7
Acoustic field at 3.3 cm from the dichroic filter.
Fig. 8
Fig. 8
Results for the wire phantom. An improvement in the lateral resolution is clearly evident by comparing the images for before (a) and after (b) applying the SAFT. Magnified images of (a) and (b) are shown in (c) and (d), respectively. The third row shows US images of the cyst-like phantom before (e) and after (f) applying the SAFT. The yellow and red boxes indicate the graphite (area 1) and agarose (area 2) regions, respectively.
Fig. 9
Fig. 9
US (a), PA (b) and fusion (c) images of the cyst-like phantom.
Fig. 10
Fig. 10
(a) 1-D linear array and (b) 2-D array all-optical US/PA scanhead designs.
See this image and copyright information in PMC

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