Symfony 3.3 and doctrine 2 - doctrine-orm

Question

I have two entities Article and Image related by a ManytoMany relations using a third entity called ArticlesHaveImages.
I don't use classical ManytoMany relation of Doctrine because I have a third field in ArticlesHaveImages called sequence.
class Article
{
/**
* #var int
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
...
...
/**
* One Article has Many articleHaveImage.
* #ORM\OneToMany(targetEntity="ArticlesHaveImages", mappedBy="article")
*/
private $images;
class Image
{
/**
* #var int
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
...
...
/**
* One Image has Many articleHaveImage.
* #ORM\OneToMany(targetEntity="ArticlesHaveImages", mappedBy="image")
*/
private $articles;
public function __construct() {
$this->articles = new ArrayCollection();
}
class ArticlesHaveImages
{
/**
* #var int
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* Many ArticlesHaveImages have One Article.
* #ORM\ManyToOne(targetEntity="Article", inversedBy="images")
* #ORM\JoinColumn(name="article_id", referencedColumnName="id")
*/
private $article;
/**
* Many ArticlesHaveImages have One Image.
* #ORM\ManyToOne(targetEntity="Image", inversedBy="articles")
* #ORM\JoinColumn(name="image_id", referencedColumnName="id")
*/
private $image;
/**
* #var int
*
* #ORM\Column(name="sequence", type="integer")
*/
private $sequence;
How do I create a form out of this ?
I want a multiple select option which all images name.
I tried :
class ArticleType extends AbstractType
{
/**
* {#inheritdoc}
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$images = $options['images'];
$builder
->add('translations', CollectionType::class, array(
'entry_type' => ArticleTranslationType::class,
'entry_options' => array('label' => false)))
->add('images', ChoiceType::class, array(
"required" => false,
"choices" => $images,
'multiple' => true,
But I get :
Could not determine access type for property "images" in class
"AppBundle\Entity\Article".
BIG THANKS !