TY  - JOUR
AB  - Implementation of hybrid imaging using optoacoustic tomography (OAT) and ultrasound (US) brings together the important advantages and complementary features of both methods. However, the fundamentally different physical contrast mechanisms of the two modalities may impose significant difficulties in the optimal tomographic data acquisition and image formation strategies. We investigate the applicability of the commonly applied imaging geometries for acquisition and reconstruction of hybrid optoacoustic tomography and pulse-echo ultrasound (OPUS) images. Optimization of the ultrasound image formation strategy using concave array geometry was implemented using a synthetic aperture method combined with spatial compounding. Experimental validation was performed using a custom-made multiplexer unit executing switching between the two modalities employing the same transducer array. A variety of array probes with different angular coverages were subsequently tested, including arrays for clinical hand-held imaging as well as stationary arrays for tomographic small animal imaging. The results demonstrate that acquisition of OAT data by mere addition of an illumination source to the common US linear array geometry may result in significant limited-view artifacts and overall loss of image quality. On the other hand, unsatisfactory US image quality is achieved with tomographic arrays solely optimized for OAT image acquisition without considering the optimal transmit-receive beamforming parameters. Optimal selection of the array pitch size, tomographic coverage and spatial compounding parameters has achieved here an accurate hybrid imaging performance, which was experimentally showcased in tissuemimicking phantoms, post-mortem mice, and hand-held imaging of a healthy volunteer. The efficient combination of the two modalities in a single imaging device reveals the true power of functional and molecular imaging capacities of OAT in addition to the morphological and functional imaging capabilities of US.
AU  - Mercep, E.
AU  - Jeng, G.*
AU  - Morscher, S.
AU  - Li, P.C.*
AU  - Razansky, D.
C1  - 46941
C2  - 39071
SP  - 1651-1661
TI  - Hybrid optoacoustic tomography and pulse-echo ultrasonography using concave arrays.
JO  - IEEE Trans. Ultrason. Ferroelectr. Freq. Control.
VL  - 62
IS  - 9
PY  - 2015
SN  - 0885-3010
ER  - 

TY  - JOUR
AB  - The characterization of the spatial and frequency response of acoustic detectors is important for enabling accurate optoacoustic imaging. In this work, we developed a hybrid method for the characterization of the spatially dependent response of ultrasound detectors. The method is based on the experimental determination of the receive-mode electrical impulse response (EIR) of the sensor, which is subsequently convolved with the corresponding spatial impulse response (SIR), computed numerically. The hybrid method is shown to have superior performance over purely experimental techniques in terms of accurate determination of the spatial and temporal responses of ultrasonic detectors, in high as well as low sensitivity regions of the sensor.
AU  - Caballero, M.A.A.
AU  - Rosenthal, A.
AU  - Bühler, A.
AU  - Razansky, D.
AU  - Ntziachristos, V.
C1  - 24967
C2  - 31741
SP  - 1234-1244
TI  - Optoacoustic determination of spatio-temporal responses of ultrasound sensors.
JO  - IEEE Trans. Ultrason. Ferroelectr. Freq. Control.
VL  - 60
IS  - 6
PY  - 2013
SN  - 0885-3010
ER  - 

TY  - JOUR
AB  - The frequency response of ultrasonic detectors is commonly calibrated by finding their sensitivity to incident plane waves at discrete frequencies. For certain applications, such as the emerging field of optoacoustic tomography, it is the response to point sources emitting broadband spectra that needs to be found instead. Although these two distinct sensitivity characteristics are interchangeable in the case of a flat detector and a point source at infinity, it is not the case for detectors with size considerably larger than the acoustic wavelength of interest or those having a focused aperture. Such geometries, which are common in optoacoustics, require direct calibration of the acoustic detector using a point source placed in the relevant position. In this paper, we report on novel cross-validating optoacoustic methods for measuring the frequency response of wideband acoustic sensors. The approach developed does not require pre-calibrated hydrophones and therefore can be readily adopted in any existing optoacoustic measurement configuration. The methods are successfully confirmed experimentally by measuring the frequency response of a common piezoelectric detector having a cylindrically focused shape.
AU  - Rosenthal, A.
AU  - Ntziachristos, V.
AU  - Razansky, D.
C1  - 6125
C2  - 28437
CY  - IEEE-Inst. Electrical Electronics Engineers Inc.
SP  - 316-326
TI  - Optoacoustic methods for frequency calibration of ultrasonic sensors.
JO  - IEEE Trans. Ultrason. Ferroelectr. Freq. Control.
VL  - 58
IS  - 2
PB  - Piscataway, NJ, USA
PY  - 2011
SN  - 0885-3010
ER  -