Axially rigid active steerable needle for high-dose-rate prostate brachytherapy
Martijn de Vries,
The Netherlands
PD-0570
Abstract
Axially rigid active steerable needle for high-dose-rate prostate brachytherapy
Authors: Martijn Vries1, Jakub Sikorski2, Sarthak Misra2, John van den Dobbelsteen1
1Delft University of Technology, Biomechanical Engineering, Delft, The Netherlands; 2University of Twente + University of Groningen and University Medical Center Groningen, Biomechanical Engineering, Enschede + Groningen, The Netherlands
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Purpose or Objective
High-dose-rate (HDR) brachytherapy (BT) implant needles are rigid and restricted
to linear insertion paths. Steerable instruments allow for precise access to
deeply-seated targets while sparing sensitive tissues and avoiding anatomical
structures. In addition, steerable instruments can enlarge the potential
patient group eligible for HDR prostate BT, as generally patients with a
prostate volume > 50-60 cm3 are excluded from this treatment
modality due to pubic arch interference (PAI). In this study, we present and
evaluate a novel omnidirectional steerable needle for HDR BT of the prostate.
Material and Methods
The instrument utilizes
the commercial HDR BT outer catheter and an inner needle with internal
compliant mechanism. This mechanism enables distal tip steering through
proximal instrument bending while preserving high axial and flexural rigidity. Active
steering of the instrument allows for adjustments of the catheter pathway and
withdrawal of the inner needle creates a work channel for remote afterloading.
Finite element analysis
evaluates the design and the prototype is validated in experiments involving
tissue simulants and ex-vivo bovine
tissue. US images are used to provide visualization and shape-reconstruction of
the instrument during the insertions.
Results
Manually controlled active
needle tip steering in inhomogeneous tissue simulants and ex-vivo tissue resulted in mean targeting errors of 1.4 mm and 2 mm
in 3D position, respectively. We found lateral tip steering up to 20 mm. The experiments
showed that the steering response of the instrument is history-independent.
Conclusion
The results indicate
that the endpoint variability of the steerable needle is similar to that of a conventional
rigid HDR BT implant needle while adding the ability to steer along curved paths.
High axial and flexural rigidity enable puncturing and path control within
various heterogeneous tissues. The developed steerable instrument has the
potential to overcome problems currently unavoidable with rigid HDR BT implant needles,
such as PAI, without major changes to the clinical workflow.