Echo Image Alt Tag

A previous developer has created a slider for a site but the issue is that there are no alt tags on the images and I have been asked to add them.

I’ve tried a few things with no success

Here is the code..

<?php if( $slider = get_page_images( get_the_id(), 'sc_banner_image', 'sc_banner_image' ) ) : ?>

  <div class="slider">

    <div class="slider-container">

      <div class="slider-inner">

        <?php foreach($slider as $slide) : ?>

          <img src="<?php echo $slide[0]; ?>" alt="<?php echo $alt_text; ?>"/>

        <?php endforeach; ?>

      </div>

    </div>

  </div>

<?php endif; ?>

Can anyone assist?