Technical Note: A simple and fast daily quality assurance solution for modulated scanning proton and carbon ion beams
Jing-Ni Chen1,2,3, Michael F Moyers1,2,3, Lien-Chun Lin1,2,3
1Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Shanghai 201321, China.
Purpose:
A typical ion beam treatment facility has multiple treatment rooms and may treat with more than one ion species, thus requiring a significant quality assurance (QA) effort. The goal of this work was to perform daily QA using a single irradiation per ion species to obtain the beam dosimetry parameters of dose per monitor unit (D/MU), range, and spot position. The X-ray alignment system should also be checked and the entire procedure performed by therapists.
Methods:
This goal was achieved by designing a jig for the Sun Nuclear Daily QA™ 3 device and combining it with specific brass boluses, a standard QA plan, and a cuboid polyethylene phantom for positioning/repositioning tests. The design of the plan used for each ion species delivery ensured that there was no interference between the tests of the various characteristics.
Results:
The 1-year monitoring results showed the proposed daily QA procedure was reliable and able to reflect each of the specified QA items of the proton and carbon ion beams. To simplify the daily analysis, the tolerances for the D/MU, beam range, and spot position (±1.5%, ±0.3 mm, ±1.5 mm, respectively) are checked using only the detector readings without the need for additional data processing.
Conclusions:
The proposed daily QA procedure was clinically implemented in our facility in April 2019 and has run smoothly for the first 2 years of operation. The total daily QA time for the four-room facility decreased from 1 to 1.5 h to 30 to 40 min and was achieved not by reducing QA tests but rather by implementing new technology and procedures permitting acquisition of multiple beam information.
