University of Twente Student Theses


Expanding the field of view during fetoscopic laser surgery

Steenis, J.L. van (2023) Expanding the field of view during fetoscopic laser surgery.

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Abstract:Background: In 10% of monochorionic diamniotic (MCDA) pregnancies, twin-to-twin transfusion syndrome (TTTS) occurs. If TTTS develops, anastomoses on the placenta mediate unidirectional blood flow between the two fetuses. TTTS has an 80-100% mortality rate and a 15-50% risk of disability in survivors without treatment. The main treatment for TTTS is fetoscopic laser surgery, which improves the survival rate of twins significantly. One of the main complications after fetoscopic laser surgery is iatrogenic preterm premature rupture of membranes (iPPROM). iPPROM occurrence depends among others on the size of the used instrument. Therefore, a fetoscope and cannula with a small diameter are chosen for fetoscopic laser surgery. A drawback of a small diameter is that it results in a small Field of View (FoV) which makes it a challenge to localise all the anastomoses. Aim: The primary objective of this graduation internship was to enhance fetoscopic laser surgery for the treatment of TTTS in MCDA pregnancies without increasing the risk of postoperative complications which led to two primary research questions: (1) "What is the impact of cannula size on the risk of PPROM after fetoscopic laser surgery in the treatment of TTTS for MCDA twin pregnancies?" and, (2) "Can a virtual environment be used in the performance evaluation of different 2D fetoscopic image stitching methods?" Method: First, a systematic review and meta-analysis were conducted to evaluate the relationship between cannula diameter and the outcomes of fetoscopic laser surgery for TTTS. With PPROM as the primary outcome and neonatal survival rate, preterm birth, and incomplete surgery as secondary outcomes. Secondly, a 3D intra-uterine virtual environment was used to simulate different scenarios of fetoscopic laser surgery. Virtual fetoscopic frames were extracted with corresponding camera position and orientation, allowing the reconstruction of a panorama of the placental surface based on camera movements. We evaluated the results with a visual inspection, the root mean squared error (RMSE), and the structural similarity index measure (SSIM). A good reconstruction was defined as RMSE 0.75. Finally, three different image stitching methods were created in MATLAB (version R2022a) and a qualitative and quantitative performance evaluation according to the reconstruction of the placental surface with camera position and orientation was conducted. The SSIM, RMSE, and the mean Euclidean distance between four recognizable points were calculated between the image stitched panorama and the camera movement based panorama. Results: The systematic review confirmed PPROM as a frequent complication of fetoscopic laser surgery, with a mean PPROM rate of 21.8. No significant differences were found for the pooled PPROM rates, but a significant increase in PPROM risk per French was found for PPROM before 34 weeks of gestation (p = 0.01). Secondly, for the placental panorama reconstruction based on camera movements a mean RMSE of 0.09, 0.11, and 0.12 was found for Euclidean, similarity, and projective transformations. In addition, these transformation types have found mean SSIM values of 0.83, 0.79, and 0.78, resulting in good overall quality for all transformation types. Finally, the results of the performance evaluation of the different image stitching techniques indicated that the Oriented Featured from Accelerated and Segments Test and Rotated Binary Robust Independent Elementary Feature (ORB) projective image stitching method produces the most favorable quantitative outcomes, with an RMSE of 0.49 ± 0.00, an SSIM of 0.73 ± 0.00 and a mean Euclidean distance of 22.09 ± 1.17. Conclusion: The findings of this study suggest that increasing the FoV by increasing the diameter of the cannula is not recommended. However, the use of a virtual environment was found to be a useful tool for evaluating various fetoscopic image stitching techniques to increase the FoV. This study presents a novel evaluation technique that has the potential for further research in this field.
Item Type:Essay (Master)
Radboudumc, Nijmegen, Netherlands
Faculty:TNW: Science and Technology
Subject:44 medicine
Programme:Technical Medicine MSc (60033)
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