3D cavitation mapping to improve laser lithotripsy for the treatment of kidney stones

Unmet Need

The prevalence of kidney stones is on the rise, having increased from approximately 4% in the 1970s to nearly 10% today. Approximately 1 in 10 of Americans will experience a kidney stone in their lifetime. Small stones usually pass on their own with the help of fluids, pain management, and medical expulsive therapy, where medication encourages stone passage. However, 10-20% of cases require surgical intervention to assist with stone clearance. Laser lithotripsy, a commonly used surgical method, breaks down stones through photothermal ablation and the collapse of cavitation bubbles. These bubbles are generated by the high-intensity laser, and their collapse generates shockwaves that damage the stone. An imaging method called passive cavitation mapping (PCM) uses the shockwaves to detect and map cavitation bubbles within the kidney. However, PCM’s inherent limitations in acoustic diffraction reduce the spatiotemporal resolution required for precise targeting which can lead to adverse events such as ineffective treatment outcome and damage to surrounding tissues. There is a need for improved three-dimensional, high resolution cavitation mapping methods to enhance the safety and effectiveness of stone treatment, minimizing complications and improving patient outcomes.

Technology

Duke inventors have developed a 3D cavitation detection method to enhance intracorporeal laser lithotripsy. This is intended to be used with existing cavitation mapping interfaces to provide real-time feedback on laser and pulse positioning, maximizing stone ablation while minimizing harm to adjacent tissue. Specifically, this method achieves 3D super-resolution passive cavitation mapping (3D-SRPCM) with a field of view 8 mm in diameter and automatic robotic tracking of the cavitation events. It offers sub-pixel accuracy of 40 μm and a temporal resolution of 0.128 μs. It can perform reconstructions 300 times faster than existing methods to ensure precise bubble-by-bubble activity to optimize stone damage. The non-linear relationship between cavitation bubble activity and damage to the stone can be leveraged by this method to improve ablation efficiency. This has been demonstrated using BegoStones (artificial kidney stones) in both free space and in a kidney mimetic. A high-speed camera was used to track bubble formation and collapse to establish the ground truth, thus confirming the accuracy of the algorithm’s cavitation mapping abilities. Overall, this technology provides a high-resolution cavitation mapping method that can be easily integrated with existing systems to enhance the safety and effectiveness of kidney stone treatments.

Other Applications

This technology could also be used for localized drug delivery, histotripsy, tumor and stone ablation from other organs like the gallbladder.

Advantages

• Three-dimensional cavitation mapping abilities to improve on-target ablation and minimize damage to adjacent tissue
• Provides spatial precision 10 times better than existing ultrasound imaging
• Provides reconstructions 300 times faster than existing mapping
• Cross-validated using high-speed cameras to determine ground truth