diff --git a/docs/source/field_analysis.rst b/docs/source/field_analysis.rst index 1a82c41c..6b938b1c 100644 --- a/docs/source/field_analysis.rst +++ b/docs/source/field_analysis.rst @@ -478,6 +478,16 @@ Symmetry is calculated over the specified field width (e.g. 80%) as set in by `` Symmetry can be positive or negative. A negative value means the right side is higher. A positive value means the left side is higher. +.. danger:: + + The official formula is above but due to a bug in pylinac, the actual result returned + is missing the 100 multiplication factor. For backwards compatibility, this is being + left as-is for now, but may change in a future version. Workarounds include: + + * Multiplying the result by 100. + * Use the newer :ref:`field-profile-analysis` module which has the correct formula for + the :ref:`point difference quotient `. + .. _siemens_protocol: Siemens diff --git a/docs/source/topics/profiles.rst b/docs/source/topics/profiles.rst index fd88a568..61214e97 100644 --- a/docs/source/topics/profiles.rst +++ b/docs/source/topics/profiles.rst @@ -317,6 +317,8 @@ Example usage: .. [#] `Gao et al Eqn 1 `__ .. [#] Doselab and SNC call this the "CAX point difference" however Doselab does not multiply by 100. Yet, at least in the case of Doselab, the example assumes the values are ~100. In Pylinac, we often assume values are ~1. In such a scenario, the resulting value is the same. +.. _point-difference-quotient: + Symmetry (Point Difference Quotient) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^