Keri Kim

New fluorescence endoscope for use in twin–twin transfusion syndrome: In vivo visualization of placental blood vessels

Twin-twin transfusion syndrome (TTTS) is a condition in which twins share blood disproportionately by the communicating vessels in the shared placenta, resulting in high fetal and perinatal mortality. Fetoscopic laser photocoagulation is performed to interrupt these communicating vessels; however, small vessels are often missed due to the poor image obtained with a fetoscope. We have developed a fluorescence endoscope capable of visualizing very small vessels, even in amniotic fluid, and we investigated its feasibility for in vivo visualization of placental vessels. Indocyanine green (ICG) was given at single doses of 0.5, 1.0, and 1.5 mg/kg, respectively, into the maternal circulation of pregnant rabbits, and the endoscope was used to identify the placental vessels. The vessels were detected within 15s after ICG injection for about 10 min. The brightness difference between the intervillous space and the umbilical vessels was significantly smaller after administration of 0.5 mg/kg than after 1.0 mg/kg (p=0.02) or 1.5 mg/kg (p=0.01). Even very small vessels (0.2mm in diameter) were detected. In conclusion, our new endoscope successfully provided a detailed view of the placental vessels in vivo. The results are promising for future TTTS laser surgery.

Wide FOV Wedge Prism Endoscope

We have developed a novel robotic endoscope system. It can be used to observe a wide field of view without moving or bending the whole endoscope system. It consists of a rigid endoscope and two wedge prisms at the distal tip. Rotating each wedge prism respectively, we can change the direction of view. Accordingly it becomes possible to observe a wide field of view even in a small space, and suited to clinical uses because it does not damage body tissues or internal organs. Wedge prisms are designed to avoid vignetting which is caused by the refraction or the reflection at prisms. The endoscope has 10 mm in diameter, and the drive unit is simply separable for the sterilization. In addition, since it has a simple and small drive unit, it does not obstruct surgeon or other surgery robots. The maximum movement of local field of view is 19deg, and global field of view is 93deg. In the evaluation experiment, we conformed that both of the image quality and the performance are acceptable

A new, safer, controllable field-of-view endoscope avoiding movement inside body cavities

One of the greatest difficulties in endoscopic surgery is the limited field-of-view (FOV) of endoscopes. During endoscopic manipulation in body cavities to expand the FOV, there is the risk of inadvertent damage to body tissues, nerves, and internal organs. The risk increases especially in surgery that is performed inside a very small cavity, or in which body tissues are very fragile. To overcome these issues, we developed a novel endoscope that can provide various FOVs without moving or bending the endoscope itself inside the body cavity and investigated the feasibility of using the new endoscope in vivo. A beam splitter was used to visualize both forward and side views, and two polarization plates and observation windows were used to avoid overlap of the two views. An endoscope having a 7-mm diameter was fabricated through which both views were clearly visualized in vivo. It took only 0.7s to change the FOV with high repeatability, with a maximum distance error of 2.8%. The new endoscope can provide forward and panoramic views without moving the endoscope; therefore, the risk of inadvertent damage to fragile body tissues can be significantly decreased.

The development of a composite-type optical fiberscope system for fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC).

Abstract We developed a new laser device using a composite-type optical fiberscope for laser surgery to treat twin-twin transfusion syndrome. The composite-type optical fiberscope (2.2 mm in external diameter) consists of a centrally located single fiber for laser treatment (0.1 mm in diameter) and its surrounding fibers for diagnosis. This fiberscope enables transmission of 40-W Yb fiber laser. The Yb fiber laser can be focused to 10mm focal length using two lenses on the tip of the fiberscope. In this research, we emitted the laser to in vivo porcine mesenteric vessel with blood flow both with an established laser fiber of 0.6-mm diameter (0.6-mm normal fiber) and with our composite-type optical fiberscope to compare the cautery performance of those devices. According to the experimental results, the composite-type optical fiberscope has a cautery efficiency equal to that of a 0.6-mm normal fiber, and it can contract the vein diameter about 35% as compared to the vein diameter before laser irradiation.

Active control of microcapsules in artificial blood vessel by producing local acoustic radiation force

Micrometer-sized microcapsules collapse upon exposure to ultrasound. Use of this phenomenon for a drug delivery system (DDS), not only for local delivery of medication but also for gene therapy, should be possible. However, enhancing the efficiency of medication is limited because capsules in suspension diffuse in the human body after injection, since the motion of capsules in blood flow cannot be controlled. To control the behavior of microcapsules, acoustic radiation force was introduced. We detected local changes in microcapsule density by producing acoustic radiation force in an artificial blood vessel. Furthermore, we theoretically estimated the conditions required for active path selection of capsules at a bifurcation point in the artificial blood vessel. We observed the difference in capsule density at both in the bifurcation point and in alternative paths downstream of the bifurcation point for different the acoustic radiation forces. Also we confirmed the microcapsules are trapped against flow with the condition when the acoustic radiation force is more than fluid resistance of the capsules. The possibility of controlling capsule flow towards a specific point in a blood vessel was demonstrated.

Blood flow measurement system for fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC)

Fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC) applies to the treatment of previable fetuses with severe twin-twin transfusion syndrome (TTTS). The ultimate goal of FLPC is selective blood flow interruption of anastomotic communicating vessels on the placenta fetoscopically. However, there has not been an established method to confirm that the blood flow is blocked, thus, it depends on the operators experience or intuition to evaluate whether the FLPC was performed successfully or not. For this issue, we have developed a composite-type optical fiberscope (2.2 mm in diameter), which has centrally-located cautery laser fiber and surrounding located fiberglasses for viewing. This fiberscope enables transmission of 50 W Yb fiber laser which can be focused to 10 mm focal length using two lenses on the fiberscope tip. In this study, we combined the fiberscope and a laser blood-flow meter, and irradiated cautery laser to porcine mesenteric vein with measuring blood flow at the same time. From the experimental results, we could quantitatively measure the blood flow before and after laser irradiation, and confirm the blood flow blocking with our system.

Polarizing Beam Splitter Endoscope for Simultaneously Observing Front and Lateral View

Fetal surgery sometimes requires multiple field-of-views (FOVs). The authors have developed an FOV extended endoscope for simultaneously observing front and lateral view with single lens system. A polarizing beam splitter (PBS) mounted at its distal end guides the rays from the two FOVs to relay lenses in orthogonal linear polarizations, and the other PBS mounted at its base separates them at eye lens systems. However, the images of the two views are superimposed because lenses rotate the direction of linear polarization. To solve the problem, the authors adopt a rectifier to cancel the rotation. Additional approaches consist of polarizing plates, image processing, and light source control. Polarizing plates improve the contrast of image by 13.8%. Light source control unit switches chip LEDs on and off. The cameras synchronized to LEDs get images alternately. Taken endoscopic movie with light source control was 30fps. By using these methods, clearer images are acquired.

Minimal invasive novel devices for advanced intrauterine fetal surgery

For advanced intrauterine fetal surgery, we have developed novel devices as “new hand” and “new eye”. As new hands, we developed a miniature bending manipulator with exchangeable distal-end effector of laser photocoagulation and forceps for safe approach and optimal procedure of intrauterine myelomeningocele repair and twin-to-twin transfusion syndrome. The manipulator performed high bending accuracy with a minimal error of 0.1 mm. In laser photocoagulation test, we confirmed ablation of underwater chicken liver surface successfully. As a new eye, we developed novel navigation system for safe and secure guidance of the high-intensity focused ultrasound (HIFU) to correct cardiac morphologic abnormalities such as hypoplastic left heart syndrome. In in vivo evaluation using beating heart of four anesthetized adult rabbits, the system successfully achieved a non-touch gross ablation and small transmural opening of the atrial septum. For future works, we will introduce new eye that is navigation system combined with a small 3D endoscope or 3D/4D ultrasound.

Study to prevent the density of microcapsules from diffusing in blood vessel by local acoustic radiation force

We have already reported our attempt to constrain direction of microcapsules in flow owing to an acoustic radiation force. However, the diameter of capsules was too large not to be applied in vivo. Furthermore, acoustic radiation force affected only in focal area because focused ultrasound was used. Thus we have improved our experiment by using microcapsules as small as blood cells and introducing a plane wave of ultrasound. We prepared an artificial blood vessel including a Y-form bifurcation established two observation areas. Then we newly defined the induction index to evaluate the difference of capsule density in two paths of downstream. As the result, optimum angle of ultrasound emission to induce to desired path was derived. And the induction index increased in proportion to the central frequency of ultrasound, which is affected by forming aggregation of capsules to receive more radiation force.

Quality evaluations on wide FOV wedge prism endoscope

Minimally invasive surgery is becoming more common nowadays. One of the important fields of minimally invasive surgery is endoscopic surgery. We have developed a novel robotic endoscope system which can be used to observe wide field of view using two wedge prisms. By rotating two wedge prisms at the distal tip of a general rigid endoscope, wide field of view can be observed without moving or bending the endoscope system itself. This makes it possible to perform the surgery safely.