def add_doserate(value, item)
      if !@current_doserate || value != @current_doserate
        @current_doserate = value
        DICOM::Element.new('300A,0115', value, :parent => item)
      end
    end
def add_doserate(value, item)
      if !@current_doserate || value != @current_doserate
        @current_doserate = value
        DICOM::Element.new('300A,0115', value, :parent => item)
      end
    end
Adds a Dose Rate Set element to a Control Point Item.
 Note that the element is only added if there is no 'current' attribute
 defined, or the given value is different form the current attribute.

 @param [String, NilClass] value the doserate attribute
 @param [DICOM::Item] item the DICOM control point item in which to create an element