Speed of ultrasound and linear attenuation measured through biomimetic bone ceramics

• Speed of sound through heterogeneous biomimetic hydroxyapatite disks • Ceramic photopolymerized disks achieved bone-like acoustic impedance • Best impedance match found in samples sintered at 900–1000 °C Transcranial focused ultrasound finds uses in the treatment of Parkinson’s disease and brain tumours. The skull is, however, a strong reflector of ultrasound. Artificial transducer layers were developed to ameliorate sound transmission through the skull. Multiple heterogeneous configurations were evaluated for their influence on the sound field in an in vitro setup comprising a water tank, a transducer, a needle hydrophone positioned distal to the natural transducer focus, and a biomimetic bone disk. The acoustic attenuation of fabricated samples was found to be lower, while the speed of sound and density of most disks were comparable to that of the human skull. Biomimetic disks fabricated by ceramic vat photopolymerization exhibited acoustic impedances close to those of bone, with the most favourable performance observed in samples sintered at 900-1000°C, where the impedance match was the strongest. This demonstrates that the disks can reduce impedance mismatch and enhance ultrasound transmission.