Compensation of Ultrasound Attenuation in Photoacoustic Imaging

Burgholzer, Peter; Roitner, H.; Bauer-Marschallinger, Johannes; Grün, Hubert; Berer, Thomas; Paltauf, Guenther

doi:10.5772/19815

Cited by 8 publications

(10 citation statements)

References 37 publications

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“…Equation 12 implies that the ultrasonic attenuation not only reduces the PA amplitude, but also broadens the PA wave temporal profile, thereby degrading the spatial resolution in acquired images (15). To improve image quality, the ultrasonic attenuation can be accounted for mathematically (18; 19). …”

Section: Principlesmentioning

confidence: 99%

Photoacoustic Microscopy and Computed Tomography: From Bench to Bedside

Wang

Gao

2014

Annu. Rev. Biomed. Eng.

212

183

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Photoacoustic imaging (PAI) of biological tissue has seen immense growth in the past decade, providing unprecedented spatial resolution and functional information at depths in the optical diffusive regime. PAI uniquely combines the advantages of optical excitation and acoustic detection. The hybrid imaging modality features high sensitivity to optical absorption and wide scalability of spatial resolution with the desired imaging depth. Here we first summarize the fundamental principles underpinning the technology, then highlight its practical implementation, and finally discuss recent advances towards clinical translation.

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Section: Principlesmentioning

confidence: 99%

Photoacoustic Microscopy and Computed Tomography: From Bench to Bedside

Wang

Gao

2014

Annu. Rev. Biomed. Eng.

212

183

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“…The mean value is described in time and space by the wave equation. For the fluctuations we describe pressure as a stochastic process; the distribution density as a function of space and time is described by a Master equation or a Langevin equation [19].…”

Section: Noise and Fluctuationsmentioning

confidence: 99%

Spatial resolution and sensitivity in photoacoustic tomography taking noise into account: from point-like detectors to large integrating detectors

et al. 2012

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As for any other imaging technique spatial resolution and sensitivity are important features for a photoacoustic imaging device. It is already well known that spatial resolution depends on the size and the bandwidth of the detectors. Therefore for photoacoustic image reconstruction usually small point-like and broadband detectors are assumed, which measure the pressure as a function of time on a detection surface around the sample. But in reality point-like detectors are not ideal at all: because of the small detector volume the thermodynamic fluctuations (= noise) get high and the signal amplitude is low, which results in a bad signal-to-noise ratio (SNR). For a bigger detector volume the fluctuations are less and the signal amplitude is better, which gives a better SNR. But on the other hand the photoacoustic pressure signal is averaged over the whole detector volume, which results in blurring and a reduced spatial resolution if reconstruction algorithms for point-like detectors are used. To characterize this trade-off between spatial resolution and sensitivity for a varying detector volume in a quantitative way the pressure is described by a random variable having the measured pressure as a mean value and noise as random fluctuations around that mean value ("stochastic process"). For a PVDF detector the optimum for the detector size is given.

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“…Burgholzer et al have directly compensated for the attenuation in photoacoustic tomography by using a time reversal finite differences method with a lossy wave equation [ 4 , 13 , 14 , 15 , 16 ]. The time reversal of the attenuation term causes the acoustic waves in the finite differences model to grow, as they propagate back in time through the tissue.…”

Section: Introductionmentioning

confidence: 99%

“…All of these attempts have one thing in common: the compensation of the frequency-dependent attenuation is an ill-posed problem that needs regularization. The physical reason for this ill-posedness is thermodynamics: acoustic attenuation is an irreversible process and the entropy production, which is the dissipated energy of the attenuated acoustic wave divided by the temperature, is equal to the information loss for the reconstructed image [ 16 ]. This also limits the spatial resolution, which correlates with the information content of the reconstructed image.…”

Section: Introductionmentioning

confidence: 99%

Resolution Limits in Photoacoustic Imaging Caused by Acoustic Attenuation

et al. 2019

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In conventional photoacoustic tomography, several effects contribute to the loss of resolution, such as the limited bandwidth and the finite size of the transducer, or the space-dependent speed of sound. They can all be compensated (in principle) technically or numerically. Frequency-dependent acoustic attenuation also limits spatial resolution by reducing the bandwidth of the photoacoustic signal, which can be numerically compensated only up to a theoretical limit given by thermodynamics. The entropy production, which is the dissipated energy of the acoustic wave divided by the temperature, turns out to be equal to the information loss, which cannot be compensated for by any reconstruction method. This is demonstrated for the propagation of planar acoustic waves in water, which are induced by short laser pulses and measured by piezoelectric acoustical transducers. It turns out that for water, where the acoustic attenuation is proportional to the squared frequency, the resolution limit is proportional to the square root of the distance and inversely proportional to the square root of the logarithm of the signal-to-noise ratio. The proposed method could be used in future work for media other than water, such as biological tissue, where acoustic attenuation has a different power-law frequency dependence.

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Compensation of Ultrasound Attenuation in Photoacoustic Imaging

Cited by 8 publications

References 37 publications

Photoacoustic Microscopy and Computed Tomography: From Bench to Bedside

Photoacoustic Microscopy and Computed Tomography: From Bench to Bedside

Spatial resolution and sensitivity in photoacoustic tomography taking noise into account: from point-like detectors to large integrating detectors

Resolution Limits in Photoacoustic Imaging Caused by Acoustic Attenuation

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