  Intracerebral hemorrhage (ICH) is the deadliest stroke sub-type, with a
one-month mortality rate as high as 52%. Due to the potential cortical
disruption caused by craniotomy, conservative management (watchful waiting) has
historically been a common method of treatment. Minimally invasive evacuation
has recently become an accepted method of treatment for patients with
deep-seated hematoma 30-50 mL in volume, but proper visualization and tool
dexterity remain constrained in conventional endoscopic approaches,
particularly with larger hematoma volumes (> 50 mL). In this article we
describe the development of ASPIHRE (A Surgical Platform for Intracerebral
Hemorrhage Robotic Evacuation), the first-ever concentric tube robot that uses
off-the-shelf plastic tubes for MR-guided ICH evacuation, improving tool
dexterity and procedural visualization. The robot kinematics model is developed
based on a calibration-based method and tube mechanics modeling, allowing the
models to consider both variable curvature and torsional deflection. The
MR-safe pneumatic motors are controlled using a variable gain PID algorithm
producing a rotational accuracy of 0.317 +/- 0.3 degrees. The hardware and
theoretical models are validated in a series of systematic bench-top and MRI
experiments resulting in positional accuracy of the tube tip of 1.39 +\- 0.54
mm. Following validation of targeting accuracy, the evacuation efficacy of the
robot was tested in an MR-guided phantom clot evacuation experiment. The robot
was able to evacuate an initially 38.36 mL clot in 5 minutes, leaving a
residual hematoma of 8.14 mL, well below the 15 mL guideline suggesting good
post-ICH evacuation clinical outcomes.
