Get alt-text on image with acf-repeater field

<?php
if( have_rows('acf_repeaterfield') ):
    while ( have_rows('acf_repeaterfield') ) : the_row();
	$imageID = get_sub_field('acf_subfield'); 
	$image = wp_get_attachment_image_src( $imageID, 'full' );
	$alt_text = get_post_meta($imageID , '_wp_attachment_image_alt', true);
?>	

	<img src="<?php echo $image[0]; ?>" alt="<?php echo $alt_text; ?>" class="port-img front" />

<?php
endwhile;
else :
  // none
endif;
?>