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The primary deep neural network architectures used to remove limited-bandwidth artifacts have been WGAN-GP [14] and modified U-net. [15] [16] The typical method to remove artifacts and denoise limited-bandwidth reconstructions before deep learning was Wiener filtering, which helps to expand the PA signal's frequency spectrum. [14]
The axial resolution of the system can be improved by using a wider bandwidth ultrasound transducer as long as the bandwidth matches that of the photoacoustic signal. The lateral resolution of photoacoustic microscopy depends on the optical and acoustic foci of the system.
This particular biomedical imaging modality is a combination of optical imaging, and ultrasound imaging. In other words, a photoacoustic (PA) image can be viewed as an ultrasound image in which its contrast depends on the optical properties, such as optical resolution of biomolecules like hemoglobin, water, melanin, lipids, and collagen.
Photoacoustic imaging or optoacoustic imaging is a biomedical imaging modality based on the photoacoustic effect.Non-ionizing laser pulses are delivered into biological tissues and part of the energy will be absorbed and converted into heat, leading to transient thermoelastic expansion and thus wideband (i.e. MHz) ultrasonic emission.
This choice of frequency band dictates whether the imaging will be in the macroscopic regime, involving resolution of 100-500 microns and penetration depth >10 mm, or mesoscopic range, involving resolution of 1-50 microns and penetration depth <10 mm. [1] [6] Microscopic resolution is also possible using multi-spectral optoacoustics.
Ultrasound Localization Microscopy (ULM) is an advanced ultrasound imaging technique. By localizing microbubbles, ULM overcomes the physical limit of diffraction, achieving sub-wavelength level resolution and qualifying as a super-resolution technique. [1] [2] ULM is primarily utilized in vascular imaging.
However, as the axial (in the direction of the beam) resolution of the ultrasound is far better than the transverse, the tracking ability is less in the transverse direction. Also, the transverse resolution (and hence, tracking ability) decreases with depth, in a sector scan where ultrasound beams diverge.
[clarification needed] We determine the size of this area by the diffraction-limited resolution of the lens which is given by the Airy disk whose diameter is 2.4λu/D, where λ is the wavelength of the light, u is the distance between the object and the lens, and D is the diameter of the lens aperture. (This is a simplified model of diffraction ...