about memory release

[bestwiz]

In the project,We use flex-iframe to display the PDF file.
Source is as follows:

flex_iframe:IFrame id="iframeLf" overlayDetection="true" source="{firstInputModel.loadOutputVO.loadCaseList.getItemAt(firstInputModel.currentIndex).firstInputJpgPathLf}" width="763" height="1057" x="0" y="-10" cachePolicy="off"

When the picture transfer,We see through the FlashProfile tool,picture Memory is not released,repeated operation,memory rising.

We use the following source clear Frame,but failed
(pages.getElementAt(0) as FirstInput).iframeNl.removeIFrame();