PURPOSE: 
To report the commissioning and implementation of the automatic gated breath-hold system using pencil beam scanning (PBS; ProBeam, Varian, USA).  
METHODS: 
Commissioning: The voluntarily breath-hold spirometry system (SDX, Dyn’R, France) with automatic gating module was commissioned at the Maryland Proton Treatment Center by performing point and 2D-planar dose measurements of 5 gated plans (3-4 fields per plan). For each field, four measurements were performed: three with 2, 3 and 5 breath-hold which were evaluated against the one without breath-hold (reference). 
Implementation: The proposed workflow of automatic gated breath-hold treatment and estimated duration time of each step were established. After instructing the patient how to breathe and hold the breath through the spirometer, the breath-hold level will be set. Next, the CT images will be acquired using SDX breath-hold system as well as normal 4D-CT (as a backup treatment) following by treatment planning on both image sets.  At the time of treatment, kV and CBCT images will be acquired at the pre-defined breath-hold level for image guidance. After the patient setup, the treatment will proceed with the automatic gating module active and connected to the ProBeam system. 
RESULTS:
The maximum percent difference of point dose measurements and the lowest gamma passing rate between non-breath-hold and breath-hold plans were 0.2% and 97.2%, respectively. Of 48 patient that were consulted for SDX treatment, 37 underwent SDX simulation and 35 were treated with SDX plan. 
CONCLUSION:
The automatic gated breath hold system was successfully commissioned and implemented for PBS proton system.

04 - Commissioning and Implementation of the Automatic Gated Breath Hold Technique for Pencil Beam Scanning Proton System