All tasks were completed.
AIM 1. Refine the ultrasound probes to detect, reposition, and fragment kidney stones.
Task 1.1. Select imaging probe for stone repositioning. We enabled the capability to push stones on the as yet incomplete NASA FUS system with the NASA GE C1-6 abdominal imaging probe. These results were reported in an NSBRI Advanced Technology Demonstration: Prevention of Renal Stone Complications in Space Exploration in August 2016.
Deliverable of the grant
The capability to reposition kidney stones noninvasively has been added to the NASA flexible ultrasound system.
Task 1.2. Custom design probe to image, reposition, and fragment stones. We invented Burst Wave Lithotripsy which has fully comminuted stones of all compositions in under 20 minutes and has fragmented many stones in seconds. All work so far has been in water tanks or animals, not humans. The size fragments are controlled by the ultrasound frequency. The technique reduces peak pressure by 1/10th but increases pulse duration about five times and pulse repletion rate at least 20 times to deliver more energy more quickly and possibly without discomfort.
AIM 2. Validate probes to visualize, reposition, and fragment kidney stones.
Task 2.1. Validate capability to displace an obstructing stone.
Task 2.2. Validate capability to displace a ureter stone.
Task 2.3. Validate capability to comminute a stone.
These tasks were completed. A small probe embedded centrally within the Burst Wave Lithotripsy (BWL) therapy probe connected to the Verasonics FUS system provides image guidance for BWL. We have targeted and fragmented human stones surgically placed in over 10 pigs. Preclinical test results have been submitted for publication. A clinical trial of the system is underway.
AIM 3. Refine and validate imaging to guide therapy.
Task 3.1. Refine and validate capability to measure the size of kidney stones. In a series of 3 papers, we demonstrated how ultrasound imaging can be optimized to accuracy similar to CT with user controls as well as software modifications. The imaging we have implemented on the Verasonics FUS appears to size stones more accurately than clinical imagers.
Task 3.2. Refine capability to localize a stone.
Task 3.3. Refine and validate capability to detect a ureter stone. We have developed enhanced B-mode, enhanced Doppler-based twinkling, and combined them into a stone specific imaging mode called S-mode. S-mode has been published. S-mode has been used to image stones in the kidneys and ureters in human subjects. In our most recent study of hundreds of imaging frames from 40 stones and 28 subjects, the signal to noise ratio of S-mode was ten times the grayscale SNR. This paper won Best Abstract at the Engineering and Urology meeting of the AUA in 2016.