Dual-modal photoacoustic and ultrasound imaging for early diagnosis of ovarian torsion and evaluation of long-term tissue hypoxia.

Ovarian torsion (OT), a critical gynecological emergency caused by ovarian twisting and vascular compromise, risks necrosis without prompt intervention. This study evaluated dual-modal photoacoustic/ultrasound imaging for early detection and chronic hypoxia monitoring in OT. Rat models of complete/partial OT were established, with photoacoustic imaging (PAI) tracking tissue oxygen saturation (sO₂) over time, compared to color Doppler parameters (color pixel density [CPD]) and spectral Doppler parameters (peak systolic velocity [PSV], resistance index [RI]). In short-term (6-hour) torsion, PAI and CPD showed similar declining trends, but PAI provided superior sO₂ quantification. In long-term models, PAI detected significant sO₂ reductions at 12 and 24 h, whereas CPD declined only within the first 12 h, highlighting PAI's enhanced accuracy for hypoxia assessment during the 12-24 h window. Histological analysis confirmed that PAI-measured hypoxia correlated with tissue injury severity. These findings demonstrate PAI's reliability in evaluating hypoxia progression and tissue damage, facilitating precise early diagnosis and time-sensitive monitoring in prolonged OT. Combining ultrasound with PAI offers a more effective diagnostic tool for assessing OT progression, particularly in guiding timely interventions for long-term torsion.