A theranostic 3D ultrasound imaging system for high resolution image-guided therapy

Microbubble contrast agents are a diagnostic tool with broad clinical impact and an increasing number of indications. Many therapeutic applications have also been identified. Yet, technologies for ultrasound guidance of microbubble-mediated therapy are limited. In particular, arrays that are capable of implementing and imaging microbubble-based therapy in three dimensions in real-time are lacking. We propose a system to perform and monitor microbubble-based therapy, capable of volumetric imaging over a large field-of-view. To propel the promise of the theranostic treatment strategies forward, we have designed and tested a unique array and system for 3D ultrasound guidance of microbubble-based therapeutic protocols based on the frequency, temporal and spatial requirements. Methods: Four 256-channel plane wave scanners (Verasonics, Inc, WA, USA) were combined to control a 1024-element planar array with 1.3 and 2.5 MHz therapeutic and imaging transmissions, respectively. A transducer aperture of similar to 40x15 mm was selected and Field II was applied to evaluate the point spread function. In vitro experiments were performed on commercial and custom phantoms to assess the spatial resolution, image contrast and microbubble-enhanced imaging capabilities. Results: We found that a 2D array configuration with 64 elements separated by lambda-pitch in azimuth and 16 elements separated by 1.5 lambda-pitch in elevation ensured the required flexibility. This design, of 41.6 mm x 16 mm, thus provided both an extended field-of-view, up to 11 cm x 6 cm at 10 cm depth and steering of +/- 18 degrees in azimuth and +/- 12 degrees in elevation. At a depth of 16 cm in B-mode, we achieved a volume acquisition rate of 60 Hz and an imaging display rate of 30 Hz. Lateral resolution was 0.8 mm at 5 cm depth and 2.1 mm at 12.5 cm. Conclusion: A single 2D array for both imaging and therapeutics, integrated with a 1024 channel scanner can guide microbubble-based therapy in volumetric regions of interest.

Automated summary

The researchers propose a system for performing and monitoring microbubble-based therapy, capable of volumetric imaging over a large field-of-view. By designing and testing a unique array and system, they demonstrate the ability to guide microbubble-based therapeutic protocols in three dimensions using ultrasound.