Remove indirectLight on Volume shader

Hi,guys.As the Volume Object (Shading as volume) lighthing method is sampling the FogStruct.IntegratedLightScattering --3D texture in Light Scattering Stage,I couldn’t be able to find any access to see how this texture was made and to remove all the indirect light from it in shaders .And the result is that my volume in scene is either always sampling all the light or no light. Any help?