Volumetric photoacoustic/ultrasound image fusion and enhancement with dual-tree complex wavelet transform.

Photoacoustic (PA) imaging is capable of visualizing the three-dimensional structures of light-absorbing objects, such as blood vessels, and it is often integrated with ultrasound (US) imaging for comprehensive anatomical and functional imaging of biological tissues. For wide field-of-view imaging, volumetric PA or US data from multiple scans are merged to image large objects, such as the entire organ of humans or the entire body of small animals. This study investigated improvements in the volumetric data-merging process of wide-field PA/US imaging using the dual-tree complex wavelet transform (DT-CWT) technique. First, it was shown to effectively suppress boundary seam artifacts in the combined scan data, enabling smooth fusion while preserving critical features. Second, a noise-reduction imaging method based on this technique was applied to effectively enhance the image contrast and spatial resolution. Finally, we demonstrated the DT-CWT-based fusion of vascular images from PA and US volumes, which provided an integrated visualization of the peripheral vasculature. These results demonstrate that DT-CWT has the potential to improve wide-field PA/US images in terms of seamless fusion of multi-scan or multi-modal volume data, enhanced visualization of structures, noise reduction, and contrast improvement.