# Units of Beam Properties in SlicerRT extension

**URL:** https://discourse.slicer.org/t/units-of-beam-properties-in-slicerrt-extension/39493
**Category:** Support
**Tags:** slicerrt
**Created:** [October 2, 2024, 12:35pm UTC](https://discourse.slicer.org/t/units-of-beam-properties-in-slicerrt-extension/39493 "2024-10-02T12:35:12Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![SCJohnson](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/scjohnson/32/78095_2.png) [@SCJohnson](https://discourse.slicer.org/u/SCJohnson)
#### Post date: [October 2, 2024, 12:35pm UTC](https://discourse.slicer.org/t/units-of-beam-properties-in-slicerrt-extension/39493/1 "2024-10-02T12:35:13Z")

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Good day. I would like to ask what is the unit of the Beams weight in RT slicer for proton therapy? I extracted data from the plan but the units for weight was not specified.  
Thank you.

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### Author: ![cpinter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/cpinter/32/7995_2.png) [@cpinter](https://discourse.slicer.org/u/cpinter)
#### Post date: [October 3, 2024, 8:56am UTC](https://discourse.slicer.org/t/units-of-beam-properties-in-slicerrt-extension/39493/2 "2024-10-03T08:56:29Z")

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It’s a relative weight of the beams within the plan. It is taken into account when accumulating per-beam doses. A dose with a weight of 1.0 is added to the accumulated final dose as is, but with a weight of 0.5 the calculated cGy values will be halved during the summation.