$images = $this->getDoctrine()->getEntityManager()
->createQuery("SELECT img, cat, u
FROM AcmeMainBundle:Image img
JOIN img.category cat
JOIN img.user u
WHERE img.title LIKE :text OR img.description LIKE :text
ORDER BY img.id DESC")
->setParameter('text', $text)
->getResult();
Или попробуйте это:
$text = "%".$text."%";
$images = $this->getDoctrine()->getEntityManager()
->createQueryBuilder()
->select(array('img','cat','u'))
->from('AcmeMainBundle:Image', 'img')
->innerJoin('img.category', 'cat')
->innerJoin('img.user', 'u')
->where('img.title LIKE :title OR img.description LIKE :description')
->orderBy('img.id','DESC')
->setParameter('title', $title)
->setParameter('description', $title)
->getResult();