All posts by Aimee Sakes

Accura: 8DOF Accurately Steerable Platform

As of today, Chronic Total Occlusions (CTO) represent the most technically challenging lesions interventionists face during Percutaneous Coronary Interventions (PCI), with considerably lower success rates (50-90%) in comparison to semi-occluded and acutely occluded arteries [1]. The main technical challenge in PCI of CTOs lies in successfully puncturing and crossing the CTO with a guidewire.

In this section we will focus on crossing challenges. For solutions to puncture the CTO, see the Pulze Hammer I, Pulze Hammer II (coming soon), Cradle Catheter (coming soon), and Wave Catheter (coming soon).

Crossing is challenging as the guidewire cannot be actively steered and deflection can thus not be compensated. This can lead, amongst others, to dissection of the blood vessel wall or subintimal crossing, in which the guidewire crosses the CTO via the blood vessel wall (between the intima and adventitia). Furthermore, it is often challenging to navigate through tortuous CTOs.

A steerable crossing device could be the solution to current crossing challenges, as it will give the interventionist the freedom to actively navigate through the vascular system and CTO freely. Therefore, a steerable prototype nicknamed the Accura was designed with an 8 Degrees Of Freedom (DOF) cable actuated tip (Ø 2 mm, L = 32 mm) divided over 4 steering segments; allowing for constructing complex S-curves. The tip contains a lumen (Ø 1 mm) to allow for the insertion of, amongst others, a balloon catheter, a guidewire, or an IntraVascular UltraSound probe (for visualization purposes). The steerable tip is connected to a rigid shaft (Ø 2 mm, L = 200 mm), which in turn is connected to the handle. The handle consists of an innovative combined locking and steering mechanism to lock the tip position in place and to precisely steer each segment separately. This construction allows for both the tip position and direction to be changed independently, allowing for a scanning movement.

The multisteerable tip has been successfully combined with a single element forward-looking IVUS transducer and Optical Shape Sensing (OSS) fiber to reconstruct a wire frame in front of the tip. This combination will allow for reconstructing and scanning a 3D volume in front of the tip, which can be used to determine the most suitable entry location. Furthermore, the addition of the OSS fiber can potentially minimize the use of X-Ray and contrast fluid during the intervention.

Even though it is still a long way towards a fully applicable clinical tool, the tests have given first insights into the possibilities and advantages of having such a tool in PCI. Currently, a multisteerable catheter is under development.

Publications:

  • Sakes A., Ali A., Janjic, J., and Breedveld P. (2018). Novel Miniature Tip Design for Enhancing Dexterity in Minimally Invasive Surgery. Journal of Medical Devices. Accepted.

Accura_device2

Volt – 3D-Printed Bipolar Laparoscopic Grasper

Developed in 2016, thickness 5 mm, complex components made by 3D-printing.

Controlling blood loss is a major challenge during laparoscopic surgery. In an effort to control blood loss, electrosurgical tools are often used. In current electrosurgical instruments, a high frequency electrical sinusoidal wave is passed through the patient’s body from an active electrode to a return electrode to minimize bleeding. Depending on the exact configuration of the electrosurgical instrument, it can be used to coagulate, cut, or destroy the tissue.

Even though current bipolar electrosurgical instruments have proven effective in minimizing blood loss, advancement is needed to improve the dexterity and adaptability of these instruments. With current advances in 3D-print processes and its integration in the medical field it has become possible to manufacture patient- and operation-specific instruments. Furthermore, by combining 3D-print technology with smart joint designs, the dexterity of the instruments can be significantly improved.

In order to overcome these challenges, we have developed the first 3D-printed steerable bipolar grasper (5 mm), named Volt, for use in laparoscopy. This 3D-printed design allows for easy adjusting of the geometry of the shaft and tip based on the patient’s anatomy and operation requirements. The grasper significantly improves dexterity by the addition of two planar joints allowing for ±65° for sideways and ±85° for up- and downwards movement. Furthermore, due to smart joint design, high bending stiffness of  4.0 N/mm for joint 1 and 4.4 N/mm for joint 2 is achieved, which is significantly higher than that of currently available steerable instruments. The tip consists of two 3D-printed titanium movable jaws that can be opened and closed with angles up to 170° and allows for grasping and coagulating of tissues. In order to actuate the joint, tip, and electrosurgical system, as well as to tension the steering cables, a ring handle was designed similarly in design to the one of Dragonflex.

In a proof-of-principle experiment, Volt was connected to a electrosurgical unit (Erbe) and was able to successfully coagulate fresh pig liver. Tissue temperatures of over 75 °C were achieved with an activation time of ~5 s.

Publications:

 

 

 

Pressure Wave Catheter for Coronary Interventions

This research project is funded by the Netherlands Organization for Scientific Research NWO.

Crossing heavily calcified occlusions, such as Chronic Total Occlusions (CTOs), is challenging, resulting in undesirably low success rates between 50% and 90% depending on the operator’s experience and the characteristics of the CTO. The most common failure mode observed in the preferred treatment, the Percutaneous Coronary Intervention (PCI), is the inability to cross the occlusion due to buckling of the guidewire. The inability to cross the CTO often leads to procedural failure and can cause damage to the blood vessel wall.

In order to prevent buckling of the crossing tool and improve the procedural success rates of PCI, we developed a novel, well-working catheter prototype that can apply a mechanical impulse, defined as the integral of a peak force over a small time interval, on the CTO during the crossing procedure. Using an impulse to dynamically load the CTO  is advantageous as the impulse strongly decreases the buckling effect and the static forces on the CTO and its environment, minimizing the risk of damage to the blood vessel wall and the surrounding tissues.

During this TTW demonstrator project we will develop our patented catheter prototype further into a  handheld clinical prototype incorporating an  adjustable tip section as well as a dedicated input mechanism allowing for generating a single impulse as well as continuously vibrating motions. The efficiency and effectiveness of the clinical prototype will be evaluated on CTO models and during ex-vivo and in-vivo animal evaluations.

 

Novel Shooting Mechanism for Tissue Puncturing

In nature multiple animals have developed intriguing shooting mechanisms for food capture, defence, and reproductive reasons. Think for example on the amazing tongue shooting capability of the chameleon and the appendage strike of the mantis shrimp.

For a full overview of innovative and interesting shooting mechanisms in nature, we would like to refer to: Shooting Mechanisms in Nature: A Systematic Review by Sakes et al. [2016]

These shooting mechanisms can offer inspiration for new ideas on the technological development of fast acceleration mechanisms in medicine. High-speed shooting mechanisms can, for example, be used for the endovascular treatment of Chronic Total occlusions (CTOs). CTOs are heavily calcified and are thus difficult to puncture and cross with the small (0.36 mm) guidewire. The required force to puncture the CTO is often higher than the buckling force of the guidewire due to the low bending stiffness (EI) and long (unsupported) length (L). As a result, the guidewire often buckles. Buckling in turn causes procedural failure since the CTO cannot be crossed. Buckling of the crossing tool may be prevented by using a high-speed crossing tools as this increases the buckling resistance of the guidewire and potentially minimizes the puncture force of the CTO.

With this in mind an innovative high-speed crossing tool was developed using nature’s shooting mechanisms as inspiration. The crossing tool (OD 2 mm) incorporates an innovative spring-driven indenter and decoupling mechanism for high-speed puncturing of the proximal cap. First tests have been very promising. The prototype hit the CTO with an average speed of 3.4 m/s and was able to deliver a maximum force of 20 N (without buckling), which is well over the required 1.5 N to puncture the CTO. Additionally, the device was tested on CTO models made out of calcium and gelatine of different consistency. Puncture was achieved with on average 2.5 strikes for heavily calcified (77 wt% calcium) CTO models.

We feel that with continued development of this technique it will become possible to deliver high forces in ultra thin devices, such as guidewires, and as such increase the success rate of the the endovascular treatment of CTOs and other minimal invasive applications.

For a video of the prototype hitting a fixed surface, please see: Velocity_Max_10fps (Converted), which is slowed down 1000x.

Interventional Ductoscopy – the EVAPORATE study

This research project is funded by the Netherlands Organization for Scientific Research NWO and the Dutch Foundation of Cancer Research KWF.

Ductoscopy is a minimally invasive micro-endoscopic technique that allows for direct visualization of the milk ducts of the breast through their natural orifices in the nipple. It can be performed under local anesthesia in daily outpatient routine and has proven to be safe with a very low risk on (mild) complications. In collaboration with the UMC Utrecht, the aim of this project is to develop novel instruments for ductoscopy to prevent women from getting breast cancer.

The Nothern Clingfish, Bio-inspired Suction Cup

The northern clingfish (Gobiesox maeandricus) is able to adhere to slippery, wet, and irregular surfaces in the marine environment. A study by Wainwright et al. (2013) found that the fish can adhere to surfaces with a broad range of surface roughness, from the finest of sandpaper, to highly irregular surfaces such as rocks. The fishes outperform manmade suction cups, which as many of us know, only adhere to smooth surfaces.

Clingfish are able to adhere to these wet and irregular surface due to their highly sophisticated suction disc. This suction disc consists of a cup with at the edge of the cup structured microvilli, similar to those of geckos. When the fish attaches to a surface, water is forced out from under the suction disc by rocking the pelvic girdle and an area of sub-ambient pressure is created. The microvilli at the edge of the disc, subsequently prevent slip of the cup or premature release by creating friction between the cup and the surface.

In this assignment we will focus on the design of a special bio-inspired suction pad for use in medical application to grip and release slippery, wet and soft tissue without damaging the structure.

Flexible Endovascular Horse Morcellator

Cushing’s disease is a naturally occurring progressive pituitary disorder that can be found in multiple species, including dogs, donkeys, horses, and humans. In horses, treatment of Cushing’s disease is aimed at controlling and reducing the severity of the clinical signs using oral medication, rather than removing the tumor from the pituitary gland (which is often performed in humans), due to the fact that to date surgical removal has been technically impossible. Therefore, a new paradigm in pituitary surgery in horses was developed in close collaboration with expert veterinarian Johannes van der Kolk of the Faculty of Veterinary Medicine of the University Utrecht. In contrast to the human vascular system, multiple superficial veins in the horse, like the facial vein, can provide direct access to the pituitary gland. This superficial vein was used to guide an innovative flexible morcellator towards the pituitary gland. Once arrived at the pituitary gland, this morcellator uses a flexible drive cable to actuate a rotating cutting blade at the tip of the instrument to resect and subsequently remove the pituitary tumors. First cadaver experiments have proven successful in inserting this instrument and removing pieces of pituitary tumor. Further research needs to be done before clinical application of the instrument can take place. Nevertheless, continued development of this approach may in time improve the quality of life of horses suffering from Cushing’s disease.

Publications

Media

 

Image Guided Interventional Treatment – IGIT

This research project is part of the iMIT program and funded by the Netherlands Organization for Scientific Research NWO. The iMIT Program, executed by a community of Dutch Universities, university medical centers, and companies, aims to develop instruments for minimally invasive interventions. The program will result in the development of interactive Multi-Interventional Tools (iMIT)  that can adapt to their environment and integrate diagnostic and therapeutic functionalities, thus permitting effective single-procedure interventions.

The IGIT project focuses on increases the success rate of Percutaneous Coronary Interventions (PCI) of Chronic Total Occlusions (CTO). In the field on cardiovascular interventions, the CTO is a subset of lesion types that is the most challenging to treat, evidenced by the low procedural success (55%–80%) depending on the techniques and experience of the physician. In comparison, the procedural success rate of non-occluded lesions is approximately 90%. The most important reason for this lower success rate is the fact that the lesion cannot be crossed by the guidewire. Different techniques with extra equipment and additional guidewires are used to increase the rate of success. E.g., a support catheter can provide extra column strength, supporting the guidewire advancement through the occlusion while maintaining its flexibility. Consequences are an increase of complications such as false lumen creation or vessel dissection. Furthermore, these procedures may take hours leading to high irradiation exposure of patient andthe physician and use of large volumes of nefrotoxic contrast dye.

The aim of the IGIT project is to develop a support catheter with triple functionality: (1) imaging with an ultrasound transducer that does not only look sideways, but also in front, so that the CTO lesion can be visualized and information from the signal can be used to uncover the better accessible areas for crossing the CTO and avoid a dissection of the arterial wall or the creation of a false lumen (ErasmusMC); (2) accurate steering of the device based on the optimal use of the information already given by the location of the device, and the situation in front and around the device (TUDelft); (3) 3D visualization of the catheter without the use of X-ray by integrating a specially designed optical fiber into the support catheter (Philips). Next to these functionalities, several innovative crossing mechanisms that are able to cross heavily calcified CTOs without buckling and with ease will be developed.

In the BITE group we will focus on the design of the steerable catheter. Various methods of steering will be investigated. These include mechanical, electrical, or shape memory materials. A requirement is to leverage the limited space available in the catheter, especially since a part of the space is being used for ultrasound transducers.Furthermore, innovative crossing methods are investigated by looking into nature.

Designs related to IGIT:

  • Pulze Hammer I
  • Pulze Hammer II (coming soon)
  • Accura (coming soon)
  • Volt (coming soon)
  • Wave Catheter (coming soon)
  • Cradle Catheter (coming soon)
  • Biopsy Needle (coming soon)

Publications related to IGIT:

Shaft Guidance for Flexible Endoscopes

Flexible endoscopes (long, slender, flexible instruments with a camera and light at the distal end, having working channels to introduce flexible instruments) are used for diagnostic and therapeutic interventions inside the human digestive system and inside the abdomen. Though used for their flexibility, the flexibility of these instruments causes several difficulties during insertion and use. During insertion, flexible endoscopes can buckle and loop, which may hamper full insertion into the patient’s body. During therapeutic interventions, the flexible endoscope fails to provide stability for surgical instruments that are introduced through the flexible endoscope.

Shaft-guidance would be a good solution because it potentially enables following a 3D trajectory without any support of the surrounding anatomy at all. Combining auto-propulsion with a rigidity control mechanism may provide improvement in applications within confined anatomies where auto-propulsion simplifies insertion and rigidifying the endoscope shaft helps to stabilize the instruments during surgery. Three potentially suitable rigidity control concepts are selected and further investigated to quantitatively and qualitatively predict the maximally achievable flexural rigidity of these rigidity control mechanisms:

Vacu-SL

FORGUIDE

PlastoLock

The thesis on this topic can be found on:
Shaft-Guidance for Flexible Endoscopes

 

Vacu-SL

In order to fully benefit from the functionalities of flexible endoscopes in surgery, a simple shaft-guide that can be used to support the flexible endoscope shaft is required. Such a shaft-guide must be flexible during insertion into the human body and rigidified when properly positioned to support the flexible endoscope shaft. A shaft-guide called ‘Vacu-SL’ was designed.

The Vacu-SL rigidity control mechanism  utilizes the flexural rigidity increase that is achieved by vacuuming foil tubes filled with small particles. In this prototype the influence of particle hardness, size, and shape on the flexural rigidity of vacuumed foil tubes filled with these particles is investigated. Experiments show that the flexural rigidity increases with the hardness and irregularity of the particles and that there may be an optimal particle size in the low particle diameter region.