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bioRxiv · 10.1101/2025.05.27.656275

Adaptive transcranial ultrasound Doppler imaging of the brain

Waasdorp, R.·Munoz-Ibarra, E.·Nelissen, F.·Heiles, B.·Gazzola, V.·Renaud, G. G. J.·Maresca, D.
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Abstract

The development of fully noninvasive, transcranial functional ultrasound (fUS) would increase the translatability and clinical potential of this neuroimaging modality. Unfortunately, transcranial fUS is hindered by skull-induced aberrations which degrade power Doppler image quality and lower sensitivity. As a result, a majority of fUS imaging studies rely on craniotomies or acoustically transparent cranial windows. To advance fUS technology further, we present an adaptive aberration correction method based on ray-tracing through 4 tissue layers (transducer lens, gel & skin, bone and brain tissue). Our method segments these layers, and estimates ultrasound wave speeds in each layer iteratively. Once a velocity model of the imaging plane of interest is retrieved, ultrafast power Doppler imaging of the brain is performed using a ray-tracing beamformer that accounts for wave refraction. We tested our method in three adult rats, and estimated wave speeds for the skin/gel layer (1628 {+/-} 7 m/s), skull bone (3247 {+/-} 110 m/s), and brain tissue (1526 {+/-} 55 m/s). After aberration correction, we measured an average adult rat skull thickness of 388 {+/-} 41 m in agreement with anatomical records. The largest improvements in Doppler imaging quality were observed in cortical brain layers adjacent to the skull, specifically lateral spatial resolution was improved by 32%. Our method consistently outperformed Doppler imaging based on traditional delay-and-sum (DAS) beamforming, which assumes a uniform sound speed.

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Waasdorp, R., Munoz-Ibarra, E., Nelissen, F., Heiles, B., Gazzola, V., Renaud, G. G. J., Maresca, D.. 2025-05-31. Adaptive transcranial ultrasound Doppler imaging of the brain. https://doi.org/10.1101/2025.05.27.656275

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