High-intensity focused ultrasound (HIFU) rays are being currently tested and used in a number of treatment procedures, and are even slated to allow bloodless surgeries without the use of scalpels or sutures in the near future. Now engineers at the University of Washington and doctors at the Harborview Medical Center, Washington, are working on a new emergency application using these ultrasound waves to repair punctured lungs.
The collaborative work is funded by the National Institutes of Health (NIH), the Department of Defense, and the National Space Biomedical Research Institute, USA. Although the researchers were concerned that the rays could be blocked by air in the lungs, their experiments showed that the punctures that occur on the surface of lungs could be corrected by ultrasound therapy.
The device used for producing the ultrasound waves is about the size of a golf ball, inserted into a handle used by the physician to scan the outside of the patient’s body. In the procedure, special lenses were used to focus the high-intensity beams at a specific spot on the patient’s lung through intact layers of tissues above the organ. These focused beams resulted in an extremely ‘hot spot’ with a tiny opening, the size and shape of a rice grain. Through this opening, the beams were used to heat up the blood cells until they sealed-off the punctured region and prevented further leakage of blood, without affecting any tissues that surround the targeted spot. The beams have been tested on pig lung-tissue and it was observed that the beams sealed-off leaks in the lung within 1-2 minutes. Almost 95% of the 70 incisions made during the experiments were found to be stable within just 2 minutes after treatment. Although these initial experiments have been impressive, researchers believe that it is too early to predict the effects of the technique, as it has not been tested on humans.
It is believed that this procedure will soon replace painful invasive procedures that are currently used for treating punctured lungs. Currently lung injuries are treated by procedures ranging from wound packing and pressure application to surgical repair by thoracotomy. Use of the ultrasound technology will help in avoiding surgery and its related morbidities.
Burgess, Zderic, and Vaezy (Ultrasound in Medicine and Biology, 2007) had worked on the use of HIFU to stop bleeding from posterior liver injuries. They used a HIFU transducer with a focal length of 3.5 cm and a frequency of 3.2 MHz, integrated with a high-resolution ultrasound-imaging probe. The experiments were conducted on pig liver after creating wedge tissue extractions on the posterior surface to induce bleeding. HIFU was used on the injured surface by positioning the device on the anterior surface of liver, and resulted in hemostasis in about 66 ± 18 seconds. The authors concluded that ultrasound image-guided HIFU wave therapy is an effective tool to treat hemorrhages at sites that are not easily accessible.
Noble et al (Journal of Trauma, 2002) studied the long-term safety of using HIFU in splenic hemostasis. They used 21 rabbits and grouped them into two categories, one that received HIFU treatment (n = 14) and the other that received sham treatment (n = 7). Sterile laparotomy and splenic exposure was done in all the 21 rabbits. Splenic incisions made in HIFU-treated rabbits were immediately exposed to 9.6 MHz HIFU until hemostasis was achieved. After the rabbits recovered from treatment, ultrasound images, blood samples, and histological samples were collected from them on 0, 1, 3, 7, 14, 28, and 60 days. Researchers observed that the injuries in all the 14 HIFU treated rabbits were hemostatic after approximately 96 seconds of ultrasound treatment. Bleeding was reported only in one animal between 3rd and 7th day after treatment, but blood analysis showed very little difference in serial hematologic or coagulation measures adopted in both the groups.
All the studies and experiments related to use of high-intensity ultrasound rays have proved that it is a very efficient method of sealing injuries and preventing leakage of blood. Research is also currently underway to test the efficacy of HIFU rays in various applications that range from numbing pain to treating cancers. Since the beams used for such therapy are ten to thousand times more powerful than those used in diagnostic imaging techniques, the safety of patients exposed to such high-intensity rays is a major concern and an area that requires further research.
References
1. Star Trek Medical Devices Uses Ultrasound to Seal Punctured Lungs. University of Washington. Last accessed September 3, 2007.
2. Burgess S, Zderic V, and Vaezy S. Image-guided Acoustic Hemostasis for Hemorrhage in the Posterior Liver. Ultrasound Med Biol. 2007 Jan;33(1):113-19.
3. Noble ML, Vaezy S, Keshavarzi A, et al. Spleen Hemostasis Using High-intensity Ultrasound: Survival and Healing. Trauma. 2002 Dec;53(6):1115-20.
