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Session: Brachytherapy - I [Return to Session]

Dynamically Moving Small Robot Arms Over the Body Contour for Novel Radiotherapy Between the Tele and Brachy Regimes

K Svisasubramanian, W Liu, K Bush, A Yu, M Shi, J Blickenstaff, M Ashraf, D Capaldi, L Skinner*, Stanford University, Stanford, CA


SU-H300-IePD-F7-6 (Sunday, 7/10/2022) 3:00 PM - 3:30 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 7

Purpose: Recent advances have brought high quality robot arms down from heavy industrial devices into smaller, lighter, packages. Here we use a small, 6-axis robot arm (5kg payload capacity, approx. 80cm range) to investigate improved radiotherapy for complex skin targets, such as the scalp and targets a few cm deep needing high conformality, such as the eye.

Methods: A Varian HDR Varisource was custom mounted onto an X-arm 6-axis robot arm using a 3D printed mount. Providing a relatively simple and relatively high-energy radiotherapy source. Custom CNC machined tungsten alloy collimators were also inserted into the mount. A robot cart and remote-control system was developed for use inside treatment vaults. To investigate and calculate dose distributions and collimation options the TOPAS monte Carlo code was used in conjunction with body contours (in .stl mesh format) converted from anonymized CT scans. Robot paths were planned using custom python code to cover example PTV volumes. Corresponding 3D printed Phantoms of the head and hand were made, and delivery was tests performed.

Results: Two modes were identified: (i) tightly collimated with circular paths (eg eye for treatments), and (ii) 3D raster scanning over the body contour (skin treatment of scalp, hands, limbs etc). For (i) high conformality and dose fall-off was achieved, with dose in the lateral direction falling to 30% at 2 mm from the target, while in the depth direction dose falls to 40% at 5 mm beyond the target and 15% at 20 mm.

Conclusion: Dynamically moving small robot arms have potential to provide much cleaner applicator-less intensity modulated skin radiotherapy, especially for complex shaped superficial targets, such as the scalp. The dose conformality for also makes this a possible surgery-free alternative for eye-plaque radiotherapy. Technical challenges lie in programming the robot paths.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by The Clinical Innovation Fund (CIF) of Stanford Cancer Center.


Not Applicable / None Entered.


TH- External Beam- Photons: Development (new technology and techniques)

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