Mucong L. et al., 2019: Simultaneous Photoacoustic Imaging and Cavitation Mapping in Shockwave Lithotripsy
Li M, Lan B, Sankin G, Zhou Y, Liu W, Xia J, Wang D, Trahey G, Zhong P, Yao J.
Abstract
Kidney stone disease is a major health problem worldwide. Shock wave lithotripsy (SWL), which uses high-energy shock wave pulses to break up kidney stones, is extensively used in clinic. However, despite its noninvasiveness, SWL can produce cavitation in vivo. The rapid expansion and violent collapse of cavitation bubbles in small blood vessels may result in renal vascular injury. To better understand the mechanism of tissue injury and improve treatment safety and efficiency, it is highly desirable to concurrently detect cavitation and vascular injury during SWL. Current imaging modalities used in SWL (e.g., C-arm fluoroscopy and B-mode ultrasound) are not sensitive to vascular injuries. By contrast, photoacoustic imaging is a non-invasive and non-radiative imaging modality that is sensitive to blood, by using hemoglobin as the endogenous contrast. Moreover, photoacoustic imaging is also compatible with passive cavitation detection by sharing the ultrasound detection system. Here, we have integrated shock wave treatment, photoacoustic imaging and passive cavitation detection into a single system. Our experimental results on phantoms and in vivo small animals have collectively demonstrated that the integrated system is capable of capturing shock wave-induced cavitation and the resultant vascular injury simultaneously. We expect that the integrated system, when combined with our recently developed internal-light-illumination photoacoustic imaging, will find important applications for monitoring shock wave-induced vascular injury in deep tissues during SWL.
IEEE Trans Med Imaging. 2019 Jul 15. doi: 10.1109/TMI.2019.2928740. [Epub ahead of print]
Comments 1
Shock wave lithotripsy is a non-invasive and gentle treatment procedure for kidney stones. Nevertheless, mild haematuria up to severe bleedings may occasionally occur during or after treatment. Cavitation is made responsible for that kind of tissue lesions. Unfortunately, fluoroscopy and/or ultrasonography do not provide sufficient information about cavitation and small bleedings during treatment. The authors make use of a special photoacoustic imaging technique to record cavitation events and effusion of blood simultaneously. They managed to combine the three modalities photoacoustic imaging, shock wave generation and cavitation detection in one unit which is intended to be used in the future for medical lithotripsy procedures. Photoacoustic imaging is sensitive to blood, which is selectively stimulated to radiate acoustical signals by absorption of a matched wavelength (1064 nm) from a Q-switched Nd:YAG laser. The goal is to detect and avoid possible small haemorrhages during lithotripsy and adjust treatment parameters accordingly.
Integration of the technique into commercial lithotripters requires further development and an extension of the working distance in the range of minimum 10 cm and more. Due to the limited penetration of applied wavelength of the optical excitation pulse, it is envisaged, to illuminate from inside the body (via the ureter?). The non-invasive feature of lithotripsy procedure would suffer. We guess, a lot of additional work is required until this interesting approach may become medical routine.