在iPhoneSDK中删除指定HTML标签

应用中的NSString中包含HTML，我想删除< img src=..../>标签的内容。
举个例子：

Source = < p>< a href="http://wpcore.mpf.s3.amazonaws.com/wp-content/uploads/2012/12/thumbs_img_0500.jpg">**< img class="alignleft size-full wp-image-4730" style="margin-left: 5px; margin-right: 5px;" title="thumbs_img_0500" src="http://wpcore.mpf.s3.amazonaws.com/wp-content/uploads/2012/12/thumbs_img_0500.jpg" alt="thumbs img 0500" width="120" height="120" />**< /a>The two professional level < a title="3d printing" href="http://www.makepartsfast.com/category/products/3d-printers/">3D printers< /a> that build parts in color are the Zprinter from 3D Systems and the < a href="http://www.makepartsfast.com/2012/05/3812/mcor-announces-full-3d-color-3d-printer">Iris< /a> from Mcor Technologies. Earlier this year, Mcor Technologies announced its Iris full color 3D printer at the Rapid show and recently at Euromold. The Zprinter uses ink jetted into the build powder. The Iris, however, uses a different technique for creating color parts. Dr. Conor MacCormack, CEO of Mcor, discusses this technology.</p>
< p>< a href="http://wpcore.mpf.s3.amazonaws.com/wp-content/uploads/2012/12/MacCormack-part-1.mp3">MacCormack part 1< /a>< /p>
其中 img src 标签都不同。怎么实现呢？
我的代码：
-(void)viewWillAppear:(BOOL)animated
{
source = [NSString stringWithFormat:@"%@",[[self.parseResults objectAtIndex:k] objectForKey:@"summary"]];

NSLog(@"%@",source);
}