Twinkling-Artifact Ultrasound Detects, Treats Kidney Stones

Kidney stones are frequently painful and sometimes difficult to remove, and 10% of the population will suffer from them. In space, the risk of developing kidney stones is exacerbated due to environmental conditions. The health risk is magnified by the fact that resource limitations and distance from Earth could restrict treatment options.

The project is led by US National Space Biomedical Research Institute (NSBRI; Houston, TX, USA) smart medical systems and technology team lead investigator Dr. Lawrence Crum and coinvestigator Dr. Michael Bailey; both are researchers at the Applied Physics Laboratory at the University of Washington (APL-UW; Seattle, USA).

Dr. Bailey stated that their technology is based on equipment currently available. “We have a diagnostic ultrasound machine that has enhanced capability to image kidney stones in the body,” said Dr. Bailey, a lead engineer at APL-UW. “We also have a capability that uses ultrasound waves coming right through the skin to push small stones or pieces of stones toward the exit of the kidney, so they will naturally pass, avoiding surgery.”

On Earth, the current preferred removal method is for patients to drink water to force the stones to pass naturally, but this does not always work, and surgery is frequently the only option. In space, the threat from kidney stones is greater due to the difficulty of keeping astronauts fully hydrated. Another factor is that bones demineralize in the reduced-gravity environment of space, dumping salts into the blood and eventually into the urine. The increased concentration of salts in the urine is a risk factor for stones.

Dr. Crum, who is a lead physicist at APL-UW, reported that kidney stones could be a serious difficulty on a long-duration mission. “It is possible that if a human were in a space exploration environment and could not easily return to Earth, such as a mission to an asteroid or Mars, kidney stones could be a dangerous situation,” Dr. Crum said. “We want to prepare for this risk by having a readily available treatment, such as pushing the stone via ultrasound.”

Before a stone can be pushed, it needs to be located. Conventional ultrasound units have a black and white imaging mode called B-mode that creates an image of the anatomy. They also have a Doppler mode that specifically displays blood flow and the motion of the blood within tissue in color. In Doppler mode, a kidney stone can appear brightly colored and twinkling. The reason for this is not known; however, the scientists are working to understand what causes the twinkling artifact image.

“At the same time, we have gone beyond twinkling artifact and utilized what we know with some other knowledge about kidney stones to create specific modes for kidney stones,” Dr. Bailey said. “We present the stone in a way that looks like it is twinkling in an image in which the anatomy is black and white, with one brightly colored stone or multiple colored stones.”

Once the stones are located, the ultrasound machine operator can select a stone to target, and then, with a simple push of a button, send a focused ultrasound wave, approximately half a millimeter in width, to move the stone toward the kidney’s exit. The stone moves about 1 cm per second. In addition to being an option to surgery, the technology can be used to “clean up” after surgery. “There are always residual fragments left behind after surgery,” Dr. Bailey said. “Fifty percent of those patients will be back within five years for treatment. We can help those fragments pass.”

The ultrasound technology being developed for NSBRI by Drs. Crum and Bailey is not restricted to kidney stone detection and removal. The technology can also be used to stop internal bleeding and ablate tumors. Dr. Crum reported that the research group has novel plans for the technology. “We envision a platform technology that has open architecture, is software-based and can use ultrasound for a variety of applications,” he said. “Not just for diagnosis, but also for therapy.”

NSBRI’s research range includes other projects seeking to develop smart medical systems and technologies, such as new uses for ultrasound that provide healthcare to astronauts in space. Dr. Crum, who served eight years as an NSBRI team leader, noted that the innovative approaches to overcome the restrictive environment of space could make an impact on Earth.

“Space has demanded medical care technology that is versatile, low-cost, and has restricted size. All of these required specifications for use in a space environment are now almost demanded by the general public,” Dr. Crum said. “One of the reasons that translation from one site to another is possible is because of NSBRI’s investment.”

Related Links:
US National Space Biomedical Research Institute
Applied Physics Laboratory at the University of Washington