Electromagnetic image guidance systems have emerged as more secure methods to improve the performance of several catheter-based minimally invasive surgical procedures. Small sensors are incorporated within catheters and guidewires in order to track and guide in real-time their position and orientation with a reduced intra- procedural radiation exposure and contrast agent injections. One of the major limits of these systems is related to the unsuitable sensorization strategy for the J-tip guidewires, due to the structural constraints of the sensor coils available on the market. In this work we present preliminary results on a sensors bending test in static conditions to assess whether and when the precision of the sensor remains unchanged and/or deteriorates. In the worst case, the highest standard deviation is less than 0:10 mm.
Laser-generated fenestration is an alternative option for the intraoperative and selective modification of a endovascular endograft, especially in cases where patients are unsuitable for a standard endovascular aneurysms repair. Recently, diode laser approach has been proposed as a substitution of mechanical fenestration. In fact, using a near infrared wavelength (810 nm), the stent graft fabric can be successfully perforated. In this work we report an ex-vivo study providing the harmlessness of laser irradiation effects on biological tissue surrounding the endograft wall. 225 samples of human aortic tissue were irradiated varying energy and pulse duration of an 810 nm diode laser. Irradiated tissues were analyzed under histological examination. Thermal damage was evidenced in the 7.5% of the irradiated samples, typically in the contact area between the laser fiber tip and the aortic wall. These experiments suggest that the diode laser can be safely used for the proposed surgical application.
Endovascular abdominal aortic aneurysms repair (EVAR) involves the minimally invasive implantation of a stent-graft
within the aorta to exclude the aneurysm from the circulation thus preventing its rupture. The feasibility of such
operation is highly dependent on the aorta morphology and in general the presence of one/both renal arteries emerging
from the aneurysm is the absolute limit for the implantation of a standard stent-graft. Consequently, classical intervention
methods involve the implantation of a custom-made graft with fenestrations, leading to extremely complicated surgeries
with high risks for the patient and high costs. Recent techniques introduced the use of standard grafts (i.e. without
fenestrations) in association with mechanical in-situ fenestration, but this procedure is limited principally by the
brittleness and low stability of the environment, in addition to the difficulty of controlling the guidance of the
endovascular tools due to the temporarily block of the blood flow. In this work we propose an innovative EVAR strategy,
which involves in-situ fenestration with a fiber guided laser tool, controlled via an electromagnetic navigation system.
The fiber is sensorized to be tracked by means of the driving system and, using a 3D model of the patient anatomy, the
surgeon can drive the fiber to the aneurysm, where the stent has been previously released, to realize the proper
fenestration(s). The design and construction of the catheter laser tool will be presented, togheter with preliminary
fenestration tests on graft-materials, including the effects due to the presence of blood and tissues.