A Registration Approach to Endoscopic Laser Speckle Contrast Imaging for Intrauterine Visualisation of Placental Vessels

Abstract

Abstract. Intrauterine interventions such as twin-to-twin transfusion syndrome procedure require accurate mapping of the fetal placental vasculature to ensure complete photocoagulation of vascular anastomoses. However, surgeons are currently limited to fetoscopy and external ultrasound imaging, which are unable to accurately identify all vessels especially those that are narrow and at the periphery. Laser speckle contrast imaging (LSCI) is an optical method for imaging blood flow that is emerging as an intraoperative tool for neurosurgery. Here we explore the application of LSCI to minimally invasive fetal surgery, with an endoscopic LSCI system based on a 2.7-mm-diameter fetoscope. We establish using an optical phantom that it can image flow in 1-mm-diameter vessels as far as 4 mm below the surface. We demonstrate that a spatiotemporal algorithm produces the clearest images of vessels within 200 ms, and that speckle contrast images can be accurately registered using groupwise registration to correct for significant motion of target or probe. When tested on a perfused term ex vivo human placenta, our endoscopic LSCI system revealed small capillaries not evident in the fetoscopic images.

Dual-display laparoscopic laser speckle contrast imaging for real-time surgical assistance

“…Additionally, the design of the laparoscope as a hand-held tool makes it more vulnerable to user movement and vibrations. Image registration has been proven to be capable of compensating for considerable motion, and in future studies this technique should be applied to our processing algorithm [5,33,34].…”

“…Laparoscopic implementation of LSCI faces difficulties due to several technical issues including laser light source integration, fiber light guide coupling, and specular reflections from the tissue surfaces. Numerous rigid endoscopic LSCI systems have been explored by several research groups [5][6][7][8]. However, their systems are designed for different application areas and thus have limitations that make them unsuitable for minimally invasive surgery.…”

“…However, their systems are designed for different application areas and thus have limitations that make them unsuitable for minimally invasive surgery. For example, the system presented by Santos et al is limited by the need for a laser source located on a separate optical axis [5]. Meanwhile, the LSCI system by Bray et al was not designed to visualize flows in individual vasculature [6].…”

In vivo laser speckle contrast imaging of microvascular blood perfusion using a chip-on-tip camera

“…As mentioned previously, we focus on LSCI and several studies have addressed the integration of the LSCI technique into an endoscope and demonstrated perfusion imaging, e.g., in the knee, 9 uterus, 10 gastrointestinal tract, 11 , 12 and deep brain. 13 While these studies highlighted the potential of LSCI for intra-surgery imaging, they relied on combining research grade (or standard vision) cameras with rigid endoscopes 9 , 10 , 11 , 12 or, in limited way, fiber image guides. 14 Direct-view into brain using miniature optics was used for deep brain imaging, but with highly disruptive endoscopy.…”

“…For example, mapping vasculature and perfusion of placenta allows for a powerful test during twin-to-twin transfusion syndrome procedure. 10 Capture and analysis of speckle patterns is also an established imaging method in ultrasound context 32 and we re-deploy it optically. Hence, this setup exploits the imaging function of (commercial) LSCI imagers while reducing the size of the required hardware components to enable assessment of internal organs or tissues or orifices within the body.…”