Photoacoustic imaging of the human placental vasculature. Issue 4 (25th November 2019) - Maneas, Efthymios
Abstract: Minimally invasive fetal interventions require accurate imaging from inside the uterine cavity. Twin‐to‐twin transfusion syndrome (TTTS), a condition considered in this study, occurs from abnormal vascular anastomoses in the placenta that allow blood to flow unevenly between the fetuses. Currently, TTTS is treated fetoscopically by identifying the anastomosing vessels, and then performing laser photocoagulation. However, white light fetoscopy provides limited visibility of placental vasculature, which can lead to missed anastomoses or incomplete photocoagulation. Photoacoustic (PA) imaging is an alternative imaging method that provides contrast for hemoglobin, and in this study, two PA systems were used to visualize chorionic (fetal) superficial and subsurface vasculature in human placentas. The first system comprised an optical parametric oscillator for PA excitation and a 2D Fabry‐Pérot cavity ultrasound sensor; the second, light emitting diode arrays and a 1D clinical linear‐array ultrasound imaging probe. Volumetric photoacoustic images were acquired from ex vivo normal term and TTTS‐treated placentas. It was shown that superficial and subsurface branching blood vessels could be visualized to depths of approximately 7 mm, and that ablated tissue yielded negative image contrast. This study demonstrated the strong potential of PA imaging to guide minimally invasive fetal therapies. Abstract : Successful therapy of twin‐to‐twin transfusion (TTTS) syndrome requires accurate imaging to guide laser photocoagulation of the anastomosing placental vessels. Here, two volumetric photoacoustic imaging systems with optical (Fabry‐Pérot) and piezoelectric ultrasound receivers were used to image human ex vivo normal and TTTS‐treated placentas. With imaging depths of approximately 7 mm, vasculature and ablated regions were visualized. The strong potential of photoacoustic imaging to guide minimally invasive fetal therapies was demonstrated.