D1 – A smart ablation catheter with optical shape sensing
Demonstrator leader: Trung Nguyen (Philips Research)
 
Introduction
With the introduction of catheter interventions, the management of rhythm disorders has experienced a significant improvement. Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, and one of the most common cardiovascular conditions overall. AF has a significant impact on the quality of life, morbidity and mortality. In developed countries, the number of individuals with AF is projected to increase exponentially over the next four decades. The prevalence of AF is very low under the age of 40 years but increases exponentially above the age of 65 years. The total AF population is projected to be 14.8 million (2012, US/Western Europe/Japan). Moreover, this prevalence is probably underestimated due to the high rate of asymptomatic and non-diagnosed arrhythmic events.
The introduction of catheter ablation for the management of AF in the 1990s yielded a significant increase in the success rate of rhythm management in AF patients. Guidelines evolved from allowing AF to persist, to controlling ventricular function (rate control) to reversing the arrhythmia into sinus rhythm (rhythm control). Novel improvements in catheter technologies and navigation systems translate into a higher success of rhythm control in AF patients (30% of those treated are AF-free after 2 years). Catheter ablation can be considered to be the only real cure for AF in many cases. Nevertheless, lifelong drug therapy often remains the first line strategy in AF patients with only 2.1% currently treated with ablation due to treatment risks and long term efficacy.
A relatively large number of catheter interventions do not achieve a successful termination of AF in the long term. This can be attributed in many cases to the incorrect placement of ablation lesions e.g. incomplete ablation, presence of gaps, erroneous position and remodeling of the heart. To further increase the effectiveness of catheter ablation, there are still technical challenges to address.
 
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The F2R technology is especially designed to bring complex electronic sensor functionality to the tip of the smallest minimal invasive instruments. Devices are made in a planer technology, and at a final stage assembled in and around the instrument. The photo shows a 360° sensitive 2 mm diameter ultra-sound microphone.
 
 
Approach
In this demonstrator product a smart ablation catheter will be fabricated which combines two innovations to increase the success rate of AF ablations: ultrasound ablation depth monitoring to accurately monitor the depth of ablation, and Optical Shape Sensing (OSS) to precisely monitor the position of the lesion during the ablation procedure. These combined technologies will allow for better monitoring and more control during ablation, decrease the risk of over or under treatment, and improve the ablation procedure efficacy.
The ultrasound system consists of a forward looking CMUT array which produces an A-line image of the ablated region. For signal processing and conditioning a dedicated ASIC will be included in the tip of the catheter. The CMUT array fabrication and the ASIC assembly will performed using the recently developed Flex-2-Rigid miniature assembly platform. Both the smart-tip as well as the shape-sensing fiber will be integrated in a steerable ablation catheter with a diameter of 7-12 F.
Optical Shape Sensing (OSS) is a revolutionary new technology to determine the location and 3D shape of a catheter inside the body during an intervention. This is realized by means of an optical fiber integrated in the catheter. OSS does not require ionizing radiation as conventionally used in X-ray imaging. In optical shape sensing light is back-scattered by Fiber Bragg Gratings (FBGs), which are written into the fiber and used to detect changes in strain along the fiber. The strain induced by the curvature of the fiber causes a spectral shift in the scattering pattern. This phase shift is measured using optical frequency domain reflectrometry (OFDR) where spatial locations along the fiber are frequency encoded and the strain along the length of the fiber can be determined by measuring spectral shifts. From these measurements it is possible to calculate real time the exact 3D shape of the catheter over its full working length within clinically relevant accuracy.
 
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In Optical Shape Sensing the exact location of a catheter is determined by means of a specially prepared optical fiber.
 
OSS is expected to have a big impact on the way minimally invasive procedures are performed. Early market validation and feedback from end-users is therefore essential. Within the context of this demonstrator project a number of complete systems will be manufactured on a pilot production line to allow for evaluation by a number of clinical partners (evaluation not included in this project). Manufacturability aspects of both the OSS catheter and the OSS interrogator system (optical networks and read-out electronics) will be addressed. Finally, considerable effort will be spent on the integration of the OSS technology and system into the Philips Cath Lab environment (Philips Cath Lab environment (Philips Medical Systems).”).
Innovation path towards safer catheters
A roadmap towards safer and improved MRI compatible catheters will be explored in a separate innovation route. Ablation depth monitoring by means of ultrasound does not require the need for a galvanic contact with the patient and is thus inherently safe.
Replacing electrical wires with optical fibers decreases the risk of ground loops and increases the safety of the patient and MRI compatibility of the instrument. In an innovation path the feasibility of also using an optical fiber to power the electronics at the tip of the catheter will be assessed. The feasibility of digital or analog optical communication between the distal catheter tip and the proximal connector will be demonstrated by the integration of a VCSEL laser in the F2R platform. State-of-the-Art LED technology will be used to convert, with reasonable efficiency, light into electricity. Ultrasound ablation is inherently safer as it eliminates the need for a galvanic contact between the catheter and the patient. Therefore, as an alternative to RF ablation, PMUT technology will be compared with CMUTs and traditional ceramic transducers in relation to their suitability for ablation. Finally, the use of advanced ALD coatings will be explored for a pin-hole free biocompatible encapsulation of smart catheters.
 
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Innovation pipeline
 
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Schematic project overview
 
Partner Role
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