static function purgeImageAlias( $cacheItem )
    {
        // 1. fetch ezcontentclass having an ezimage attribute
        // 2. fetch objects of these classes
        // 3. purge image alias for all version

        $imageContentClassAttributes = eZContentClassAttribute::fetchList(
            true,
            array(
                'data_type' => 'ezimage',
                'version' => eZContentClass::VERSION_STATUS_DEFINED
            )
        );
        $classIds = array();
        $attributeIdentifiersByClass = array();
        foreach ( $imageContentClassAttributes as $ccAttr )
        {
            $identifier = $ccAttr->attribute( 'identifier' );
            $ccId = $ccAttr->attribute( 'contentclass_id' );
            if ( !isset( $attributeIdentifiersByClass[$ccId] ) )
            {
                $attributeIdentifiersByClass[$ccId] = array();
            }
            $attributeIdentifiersByClass[$ccId][] = $identifier;
            $classIds[] = $ccId;

        }

        $subTreeParams = array(
            'ClassFilterType' => 'include',
            'ClassFilterArray' => $classIds,
            'MainNodeOnly' => true,
            'IgnoreVisibility' => true,
            'LoadDataMap' => false,
            'Limit' => 100,
            'Offset' => 0
        );
        $count = 0;
        while ( true )
        {
            $nodes = eZContentObjectTreeNode::subTreeByNodeID( $subTreeParams, 1 );
            if ( empty( $nodes ) )
            {
                break;
            }
            foreach ( $nodes as $node )
            {
                call_user_func( $cacheItem['reporter'], '', $count );
                $object = $node->attribute( 'object' );
                self::purgeImageAliasForObject(
                    $cacheItem, $object, $attributeIdentifiersByClass[$object->attribute( 'contentclass_id' )]
                );
                $count++;
            }
            eZContentObject::clearCache();
            $subTreeParams['Offset'] += $subTreeParams['Limit'];
        }
        self::clearImageAlias( $cacheItem );
    }