All posts by Aimee Sakes

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.

 

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.

Nowadays, ductoscopy is only used as a diagnostic tool in patients suffering bloody nipple discharge, usually caused by small intraductal lesions, such as papillomas. Ductoscopy has the potential to become a preventive interventional approach to detect premalignant lesions,  but this is hampered by the limitations of the currently available instrumentation and the small size of the ducts. In collaboration with the UMC Utrecht we will develop a set of novel instruments for ductoscopy aimed at discovering, diagnosing and removing premalignant lesions in milk ducts of high risk women, thus possibly preventing them from getting breast cancer.

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.

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.

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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.

Shape Shifting in Nature; Creating a Stabile Platform inside the Vasculature

In nature many animals are able to change their appearance to match their surroundings or to mimic other animals. This camouflage protects them from predators and allows for sneaking up on unsuspected prey. Examples of these animals are chameleons and octopi.

A shape shifting/adaptable device could be an asset in the Percutaneous Coronary Interventions (PCI). In PCI, an occlusion of one of the coronaries is crossed using a guidewire (a small metal wire with a diameter of in between 0.36-0.89 mm) and, subsequently compressed against the blood vessel wall using a balloon catheter, also known as balloon angioplasty.

On some occasions, the guidewire buckling can occur during the crossing procedure, which ultimately can result in procedural failure. In order to prevent guidewire buckling, a support structure should be created that can adapt to the blood vessel wall and provide sufficient support.

Inspiration can be drawn from animals that are able to actively change their shape. This knowledge can later be used in the design of the adaptive support structure.

Contact: Aimée Sakes, a.sakes@tudelft.nl

Mechanical Reconstruction of a Chameleon Tongue (Closed)

Chameleons are able to shoot their tongues with accelerations of up to 50g to capture prey. To do this, they use a very specialized mechanism, involving elastic structures and muscle activation. A similar system is currently not seen in any other mechanical product or medical instrument. A shooting mechanism, similar to that of a chameleon can give important insights into new ways to accelerate projectiles.

Therefore, the goal of this research project is to design a mechanical shooting mechanism with similar characteristics using the chameleon’s tongue as inspiration.

Contact: Aimée Sakes, a.sakes@tudelft.nl

Chameleon copy