Do I need to free any memory using InteropServices in this instance?

               IntPtr ptrData = m.WParam;
               SizeHeight imgType = new SizeHeight();
               SizeHeight imgData;
               imgData = (SizeHeight)Marshal.PtrToStructure(ptrData,
imgType.GetType());
               WriteLog(m.Msg + " - From WndProc - " +
imgData.dwHeight.ToString());
               imgType = null;
               imgData = null;