Localisation of multiple non-isolated microbubbles with frequency decomposition in super-resolution imaging

Harput, Sevan; Christensen-Jeffries, Kirsten; Brown, Jemma; Eckersley, Robert J.; Dunsby, Christopher; Tang, Meng‐Xing

doi:10.1109/ultsym.2017.8091727

Cited by 2 publications

References 5 publications

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Understanding the effects of microbubble concentration on localization accuracy in super-resolution ultrasound imaging

Lerendegui,

Yan,

Stride

et al. 2024

Phys. Med. Biol.

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Super-Resolution Ultrasound (SRUS) through localising and tracking of Microbubbles (MBs) can achieve sub-wavelength resolution for imaging microvascular structure and flow dynamics in deep tissue in-vivo. The technique assumes that signals from individual MBs can be isolated and localised accurately, but this assumption starts to break down when the MB concentration increases and the signals from neighbouring MBs start to interfere. The aim of this study is to gain understanding of the effect of MB-MB distance on ultrasound images and their localisation. Ultrasound images of two MBs approaching each other were synthesised by simulating both ultrasound field propagation and nonlinear MB dynamics. Besides the distance between MBs, a range of other influencing factors including MB size, ultrasound frequency, transmit pulse sequence, pulse amplitude and localisation methods were studied. The results show that as two MBs approach each other, the interference fringes can lead to significant and oscillating localisation errors, which are affected by both the MB and imaging parameters. When modelling a clinical linear array probe operating at 6MHz, localisation errors between 20 to 30 µm (∼1/10th wavelength) can be generated when MBs are ∼ 500µm (2 wavelengths or ∼ 1.7 times the Point Spread Function (PSF)) away from each other. When modelling a cardiac probe operating at 1.5 MHz, the localisation errors were as high as 200 µm (∼1/5th wavelength) even when the MBs were more than 10 wavelengths apart (2.9 times the PSF). For both frequencies, at smaller separation distances, the two MBs were misinterpreted as one MB located in between the two true positions. Cross-correlation or Gaussian fitting methods were found to generate slightly smaller localisation errors than centroiding. In conclusion, caution should be taken when generating and interpreting SRUS images obtained using high agent concentration with MBs separated by less than 1.7 to 3 times the PSF, as significant localisation errors can be generated due to interference between neighbouring MBs.

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Understanding the effects of microbubble concentration on localization accuracy in super-resolution ultrasound imaging

Lerendegui,

Yan,

Stride

et al. 2024

Phys. Med. Biol.

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Two stage sub-wavelength motion correction in human microvasculature for CEUS imaging

Harput¹,

Christensen-Jeffries²,

Li³

et al. 2017

2017 IEEE International Ultrasonics Symposium (IUS)

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Abstract-The structure of microvasculature cannot be resolved using clinical B-mode or contrast-enhanced ultrasound (CEUS) imaging due to the fundamental diffraction limit at clinical ultrasound frequencies. It is possible to overcome this resolution limitation by localizing individual microbubbles through multiple frames and forming a super-resolved image. However, ultrasound super-resolution creates its unique problems since the structures to be imaged are on the order of 10s of µm. Tissue movement much larger than 10 µm is common in clinical imaging, which can significantly reduce the accuracy of superresolution images created from microbubble locations gathered through hundreds of frames.This study investigated an existing motion estimation algorithm from magnetic resonance imaging for ultrasound superresolution imaging. Its correction accuracy is evaluated using simulations with increasing complexity of motion. Feasibility of the method for ultrasound super-resolution in vivo is demonstrated on clinical ultrasound images. For a chosen microvessel, the super-resolution image without motion correction achieved a sub-wavelength resolution; however after the application of proposed two-stage motion correction method the size of the vessel was reduced to half.

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Localisation of multiple non-isolated microbubbles with frequency decomposition in super-resolution imaging

Cited by 2 publications

References 5 publications

Understanding the effects of microbubble concentration on localization accuracy in super-resolution ultrasound imaging

Understanding the effects of microbubble concentration on localization accuracy in super-resolution ultrasound imaging

Two stage sub-wavelength motion correction in human microvasculature for CEUS imaging

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