Our solution looks like this: The setup fields are defined as normal treatment fields, but with only 1 MU, which is linked to a site dose of 0.01Gy in the relating sites. [This fits all setup field doses we have been using. But these values can be changed, to get the desired dose to this site, which is a separate PV site for different reasons.] This MU will never get treated, instead, we acquire the images in port mode. Only in port mode, we are flexible regarding the number of portal images.