Benefits of the REFoCUS beamforming algorithm

Software beamforming in medical ultrasound imaging allows more sophisticated algorithms and better ways to exploit the raw channel data recorded with the ultrasound probe. A quite recent beamforming algorithm, known as REFoCUS can decode any set of transmit ultrasound beams into the “complete data set”, also known as a Synthetic Transmit Aperture Imaging (STAI) dataset. REFoCUS stands for Retrospective Encoding For Conventional Ultrasound Sequences and was introduced by Nick Bottenus is the paper 

Bottenus, N. "Recovery of the complete data set from focused transmit beams". IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 65, no. 1, pp. 30-38, Jan. 2018. 

And extended in the paper 

Ali, R.; Dahl, J.; Bottenus, N. "Extending Retrospective Encoding For Robust Recovery of the Multistatic Dataset". IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 67, no. 5, pp. 943-956, Dec. 2019.

The authors have provided open source code and datasets of their algorithm at https://github.com/nbottenus/REFoCUS. The specific task for the master project is to modify the open source implementation of REFoCUS to work with the UltraSound ToolBox (USTB) and compare it with the more conventional Retrospective Transmit Beamforming (RTB) implemented in the USTB. It is interesting to investigate if REFoCUS have benefits over conventional RTB or if they result in quite similar images. It is also interesting to investigate potential benefits for adaptive beamformers. 

Qualifications:

  • Excellent MATLAB programming skills (Object oriented MATLAB)
  • Signal processing (IN3190/4190, INF4480, IN5450, and preferably IN3015/4015)
  • Git Version Control

Literature (for example):

  • Bottenus, N. "Recovery of the complete data set from focused transmit beams". IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 65, no. 1, pp. 30-38, Jan. 2018. 
  • Ali, R.; Dahl, J.; Bottenus, N. "Extending Retrospective Encoding For Robust Recovery of the Multistatic Dataset". IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 67, no. 5, pp. 943-956, Dec. 2019.
  • Rindal, O. M. H., Rodriguez-Molares, A., & Austeng, A. (2018). A simple , artifact-free , virtual source model. IEEE International Ultrasonics Symposium, IUS, 1–4.
Emneord: ultrasound, imaging, beamforming, USTB
Publisert 14. sep. 2022 09:00 - Sist endret 26. sep. 2022 12:53

Veileder(e)

Omfang (studiepoeng)

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When forming an ultrasound image, sound is transmitted into the medium and the echoes are recorded. An image is typically formed using several transmit events. Usually, several transmitting elements are combined to form the transmitted pulse. The signal on each transmitter element is delayed in order to steer and focus the transmitted puls towards a given point as illustrated:
 

Transmit beamforming

On receive, the data is recorded on several receive elements and delayed relative to the differences in the path lengths in order to receive an echo from a given position as illustrated:

Receive beamforming

Ideally, one wants to transmit a focused beam toward every location that are to be imaged. This is too time consuming. Alternatively, one could transmit on one-and-one transmit element and receive on all elements. Then it is possible to synthesize (in a computer) focused transmit pulses to any location. This is known as Synthetic Transmit Aperture Imaging (STAI). Drawbacks with this approach are limitations on the energy it is possible to transmit using a single element and possible motion errors. The REFoCUS algorithm tries to get the best out of both these methods by acquiring data using focused beams (many elements transmitting at the same time), and convert the dataset to one that mimic the one obtained using STAI.