In‐utero imaging of developing mouse embryos using a 34‐MHz annular array and chirp‐coded excitation.

High‐frequency ultrasound (HFU) is becoming a prevalent modality to image biological tissues with fine resolution. HFU imaging is routinely used for ophthalmologic, dermatological, and small‐animal applications. Fine‐resolution imaging is obtained at the expense of limited depth‐of‐field and acoustic penetration depth. In this study, a 34‐MHz, five‐element annular array was excited using chirp‐coded signals and a synthetic‐focusing algorithm was used to form images. This imaging approach allowed for the simultaneous increase of depth‐of‐field and penetration depth. Three‐dimensional ultrasound datasets of 12.5‐day‐old mouse‐embryo heads were acquired in utero using chirp and conventional excitations. From the synthetically focused images, brain ventricles and embryonic head were segmented and rendered in three dimensions. Significant artifacts such as segmenting ventricles outside the embryonic head were significantly more pronounced on the conventional‐imaging reconstruction than on the chirp‐based reconstruction. Furthermore, the total ventricle volume obtained with the chirp (6.3 mm³) was similar to that estimated using a μMRI dataset (i.e., 7.5 mm³). The conventional method greatly over evaluated the ventricle volume (11.4 mm³). The results of this study suggest that HFU chirp‐annular‐array imaging could become a valuable method for medical imaging applications, such as in utero developmental biology. [Work supported by NIH Grants EB006509 and EB008606.]