An algorithm for computing customized 3D printed implants with curvature constrained channels for enhancing intracavitary brachytherapy radiation delivery

Abstract

Abstract-Brachytherapy is a widely-used treatment modality for cancer in many sites in the body. In brachytherapy, small radioactive sources are positioned proximal to cancerous tumors. An ongoing challenge is to accurately place sources on a set of dwell positions to sufficiently irradiate the tumors while limiting radiation damage to healthy organs and tissues. In current practice, standardized applicators with internal channels are inserted into body cavities to guide the sources. These standardized implants are one-size-fits-all and are prone to shifting inside the body, resulting in suboptimal dosages. We propose a new approach that builds on recent results in 3D printing and steerable needle motion planning to create customized implants containing customized curvature-constrained internal channels that fit securely, minimize air gaps, and precisely guide radioactive sources through printed channels. When compared with standardized implants, customized implants also have the potential to provide better coverage: more potential source dwell positions proximal to tumors. We present an algorithm for computing curvature-constrained channels based on rapidly-expanding randomized trees (RRT). We consider a prototypical case of OB/GYN cervical and vaginal cancer with three treatment options: standardized ring implant (current practice), customized implant with linear channels, and customized implant with curved channels. Results with a twoparameter coverage metric suggest that customized implants with curved channels can offer significant improvement over current practice.

Motion planning with sequential convex optimization and convex collision checking

“…We accomplish this by iteratively optimizing over increments to the trajectory, defined in terms of the corresponding Lie algebra (se( 3) in our case) (Saccon et al, 2013). Second, we consider the problem of planning multiple trajectories that are mutually collision-free, which arises in planning trajectories for multiple needles for medical procedures (Xu et al, 2009), multiple channels in intracavitary implants (Garg et al, 2013), or simultaneously planning for multiple UAVs (Shanmugavel et al, 2007).…”

“…Instead of numerically computing the gradient, we linearize the signed distance using the contact normaln. We include the continuoustime non-convex no-collisions constraint is included as a trajectory to ensure that catheters carrying the radioactive source can be pushed through the channels without buckling (Garg et al, 2013).…”

“…The dimensions of the implant was designed based on dimensions reported by Garg et al (2013). We placed three tumors and picked eight (oriented) target poses inside 9.8 ± 8.1 1.8 ± 1.2 1.6 ± 1.7 1.9 ± 1.3 1.8 ± 1.7 Path length: cm 11.1 ± 1.5 11.3 ± 1.4 11.6 ± 1.7 11.9 ± 1.7 13.1 ± 2.3 Twist cost: radians 34.9 ± 10.0 1.4 ± 1.4 1.0 ± 1.0 1.6 ± 1.6 1.0 ± 1.0 Clearance: cm 0.5 ± 0.4 0.7 ± 0.5 0.5 ± 0.3 1.3 ± 0.4 1.2 ± 0.5 54.6 ± 3.1 53.9 ± 2.5 56.5 ± 3.4 Twist cost: radians 168.3 ± 28.4 3.8 ± 1.5 2.5 ± 1.8 Clearance: cm 0.1 ± 0.08 0.1 ± 0.03 0.1 ± 0.06 the implant.…”

“…First, we considered the problem of planning collision-free, constant curvature trajectories that avoid obstacles in the environment and optimize clinically relevant metrics for flexible, bevel-tip medical needles (Webster et al, 2006;Reed et al, 2011) (Figure 1(e)). Our second application considers the problem of planning multiple, mutually collisionfree, curvature-constrained channels within 3-D printed implants (Garg et al, 2013) for intracavitary brachytherapy (HDR-BT).…”

Exact reachability analysis for planning skew-line needle arrangements for automated brachytherapy

“…We have worked on several aspects of the problem: treatment planning [4,13], needle configuration planning [5,14], robotic needle placement [6,15], and recently the use of custom guides for brachytherapy needle placement [16,17].…”