Acute Effects of Cavitation-based Focused Ultrasound on Vitreous Hemorrhage: A Preclinical Study.

OBJECTIVE: To investigate the immediate effects of a cavitation-based focused ultrasound (FUS) therapy for targeting vitreous hemorrhage (VH) in preclinical models. METHODS: A purpose-built FUS system was tested in two preclinical models of VH: ex vivo porcine eyes and in vivo rabbit eyes. In both models, VH was induced by injecting autologous blood into the vitreous humor, which was subsequently targeted and fragmented using FUS. The treatment was monitored by ultrasound B-mode imaging, which determined the treatment endpoint based on corresponding decrease in echogenicity of the hemorrhage area. After the treatment, the porcine samples were examined grossly and analyzed for the degree of vitreous liquefaction, while the rabbit eyes received histological analysis. RESULTS: The FUS treatment liquefied porcine vitreous significantly (p < 0.01). Both treated porcine and rabbit eyes showed a decrease in average pixel intensity over the targeted hemorrhage area by about 30% shown on ultrasound B-mode imaging after treatment. The average peak negative pressure was 23.1 MPa in the porcine model and 32.5 MPa in the rabbit model. No significant acute damage was discovered within the cornea, lens and retina of the treated eyes. B-mode imaging-based cavitation detection correlated significantly (p < 0.01) with conventional passive cavitation detection. CONCLUSION: This study describes the immediate effects of cavitation-based focused ultrasound therapy in ex vivo and in vivo eyes with vitreous hemorrhage, demonstrating the ability to precisely fragment a focal hemorrhage area to a diffuse one, while also liquefying the vitreous, with no consistent damage to adjoining structures.