Brain ultrasound imaging through sonolucent cranial implants: a review and perspective

Brain ultrasonography has historically been limited by strong skull-induced attenuation and phase aberration, restricting its clinical application to narrow acoustic windows such as the temporal bone. The emergence of sonolucent cranial implants used in cranioplasty has introduced a new paradigm in which the implant itself serves as a postoperative acoustic window. Over the past decade, clinical studies have demonstrated the feasibility of transimplant (or transcranioplasty) B-mode imaging, Doppler-based vascular assessment, and contrast-enhanced ultrasound in patients with sonolucent implants. Beyond currently validated modalities, transimplant access broadens the scope of ultrasound applications in adult neuroimaging, enabling the extension of advanced techniques such as ultrasound localization microscopy, shear-wave elastography, quantitative ultrasound, and therapeutic ultrasound. Although sonolucent implants substantially reduce attenuation relative to the native skull, incomplete acoustic matching with brain tissue still introduces propagation-related distortions, and technical challenges remain. We summarize current applications of transimplant imaging, explore potential future modalities, and examine key technical challenges-including geometric coupling and implant-induced acoustic effects-along with future engineering strategies. By integrating clinical evidence with acoustic principles and technical considerations, this review provides an overview of the opportunities and challenges of brain ultrasound imaging through cranial implants.