Validation of the measurement setup
The accuracy of the setup for measuring the force applied to the
platform was validated in the air by measuring standard weights, which
were put on the platform. The validation procedure is detailed further
in the online supplement.
Ablation catheter models
Four ablation catheter models were investigated. Each model was used in
conjunction with the corresponding equipment needed to read out the
force sensor. Tacticath™ Quartz, Smarttouch®, and
Stablepoint™ must all be paired with a specific 3D mapping system while
the AcQBlate® Force can be used as a standalone
solution. An overview of additional technical details can be found in
table 1.
All four catheter models provide a force sensing tip, temperature
measurement, irrigation, and catheter deflection. However, the force
sensing technology is different for each model and described in the
following section as well in Figure 2:
Tacticath™ Quartz (Abbott,
Abbott Park, IL, USA):
A beam of light is emitted by the TactySys™ system and
travels through three optical fibers towards the catheter’s tip into a
complex, deformable 3-D structure incorporating three Fabry-Pérot
interferometers made of two semi-reflective parallel surfaces. When a
force is applied to the catheter tip, the flexible titanium-alloy
structure deforms, changing its length and, therefore, the reflected
interference pattern. By knowing the deformation characteristics, both
the magnitude and orientation of the acting contact force can be
computed.
AcQBlate® Force
(Biotronik, Berlin, Germany):
The tip is suspended by a Z-Axis (In-axis to the catheter) sensor that
is realized by a deformable parallelogram, sensitive to axial forces on
the catheter. Additionally, separate X- and Y-Axis sensors are located
more proximally along the shaft. They are sensitive to lateral forces
only. One single optical fiber, incorporating a fiber Bragg grating
(FBG) runs through the deformable sensors. At each sensor, a different
wavelength is reflected. As soon as the catheter tip is exposed to a
force, the fiber changes its length at the respective section, therefore
shifting the reflected wavelength along the spectrum. Knowing the forces
along all axes, the acting force vector can be calculated.