Interventional Photoacoustic Imaging of the Human Placenta with Ultrasonic Tracking for Minimally Invasive Fetal Surgeri
Image guidance plays a central role in minimally invasive fetal surgery such as photocoagulation of inter-twin placental anastomosing vessels to treat twin-to-twin transfusion syndrome (TTTS). Fetoscopic guidance provides insufficient sensitivity for imag
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Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom 2 Translational Imaging Group, Centre for Medical Image Computing, Department of Medical Physics and Biomedical Engineering, University College London, Wolfson House, London WC1E 6BT, United Kingdom 3 Institute for Women’s Health, University College London, 86-96 Chenies Mews, London WC1E 6HX, United Kingdom 4 Department of Obstetrics and Gynecology, University Hospitals KU Leuven, Leuven, Belgium [email protected]
Abstract. Image guidance plays a central role in minimally invasive fetal surgery such as photocoagulation of inter-twin placental anastomosing vessels to treat twin-to-twin transfusion syndrome (TTTS). Fetoscopic guidance provides insufficient sensitivity for imaging the vasculature that lies beneath the fetal placental surface due to strong light scattering in biological tissues. Incomplete photocoagulation of anastamoses is associated with postoperative complications and higher perinatal mortality. In this study, we investigated the use of multi-spectral photoacoustic (PA) imaging for better visualization of the placental vasculature. Excitation light was delivered with an optical fiber with dimensions that are compatible with the working channel of a fetoscope. Imaging was performed on an ex vivo normal term human placenta collected at Caesarean section birth. The photoacoustically-generated ultrasound signals were received by an external clinical linear array ultrasound imaging probe. A vein under illumination on the fetal placenta surface was visualized with PA imaging, and good correspondence was obtained between the measured PA spectrum and the optical absorption spectrum of deoxygenated blood. The delivery fiber had an attached fiber optic ultrasound sensor positioned directly adjacent to it, so that its spatial position could be tracked by receiving transmissions from the ultrasound imaging probe. This study provides strong indications that PA imaging in combination with ultrasonic tracking could be useful for detecting the human placental vasculature during minimally invasive fetal surgery.
c Springer International Publishing Switzerland 2015 N. Navab et al. (Eds.): MICCAI 2015, Part I, LNCS 9349, pp. 371–378, 2015. DOI: 10.1007/978-3-319-24553-9_46
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Introduction
Image guidance is a central component of minimally invasive fetal surgery for treatment of twin-to-twin transfusion syndrome (TTTS). The gold standard for treatment involves laser photocoagulation of anastamosing vessels on the fetal side of the placenta [1]. In current practice, anastomosing vessels are identified with vessels along the equator using a fetoscope. Due to the limitations of this modality, there is a risk that sub-surface vessels that are small and those that are at the periphery of the placenta are missed, so that treatment is incomplete. Ultrasound (US) imaging with a probe positioned at the external surface of the mother provides inadequate visualization for smal
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