Click here to


Are you sure ?

Yes, do it No, cancel

Integration and Testing of Dynamic Collimation System Controller for Pencil Beam Scanning Proton Therapy

K Patwardhan*, T Geoghegan, R Flynn, D Hyer, University of Iowa Hospitals and Clinics, Iowa City, IA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: To integrate and test the Dynamic Collimation System (DCS) controller with the DCS mechanical assembly and a clinical IBA (Louvain-La-Neuve, Belgium) proton therapy system. The controller precisely positions four trimmer blades within a required tolerance of ±0.5 mm before each spot delivery for Pencil Beam Scanning Proton Therapy (PBS-PT) to maximize the improvement in lateral dose falloff.

Methods: A DCS prototype was built consisting of two pairs of orthogonal nickel trimmers moved by linear motors. The motors were interfaced with the DCS controller using ACS Motion Control (Yokneam Illit, Israel) software. Motor specifications were used to configure and tune the controller. The DCS controller was then interfaced with the real-time IBA scanning controller using the analog input/output (I/O) modules of the DCS controller. The interface was tested and verified by the IBA scanning controller providing set-points to the DCS controller in the form of trimmer positions and receiving real-time feedback on the actual trimmer positions. The motors were also stress-tested and characterized further for their speed and positional accuracy to identify the latency of the DCS and determine the motion parameters for best results.

Results: Maximum values of motion parameters that resulted in a system that could be tuned to be critically damped were velocity = 3,000 mm/s, acceleration = 40,000 mm/s² and jerk (time derivative of acceleration) = 50,000 mm/s³. Positional accuracy of the DCS controller was found to be within ±0.035 mm and latency of the DCS controller was found to be 0.6 ms with these settings.

Conclusion: The DCS controller can be integrated with a commercial IBA PBS-PT system and used to accurately and automatically position the trimmers for treatment delivery, ultimately improving dose conformity.

Funding Support, Disclosures, and Conflict of Interest: Research reported in this abstract was supported by the National Cancer Institute of the National Institutes of Health under award number R37CA226518. Hyer and Flynn are co-inventors on a patent that has been licensed to IBA.


Collimation, Beam Shaping, Penumbra


TH- External Beam- Particle/high LET therapy: Proton therapy – Development (new technology and techniques)

Contact Email