get_intermediate_image_sizes Get the Size Names but How Do I Get the Sizes?

I’m setting up a widget that allows to add an image to a sidebar / widget area.

Basically I have a dropdown that allows the user to select one of the available sizes inside the theme’s functions.php file using add_image_size().

Apart from the obvious ( renaming all the add_image_size() ) is there a way to get the size so that I can display that as well as the name?

This is my current drop down code:

<?php       
    $sizes = get_intermediate_image_sizes();
    $available_size="<select name="" . $this->get_field_name('image') . '" >' . "\r\n";
    $available_size .= '<option value="0" selected="selected">Choose</option>' . "\r\n";
    foreach ( $sizes as $size ) {
        if ( $instance['size'] == $size ) :
            $available_size .= '<option value="' . $size . '" selected="selected">' . $size . '</option>' . "\r\n";
        else :
            $available_size .= '<option value="' . $size . '">' . $size . '</option>' . "\r\n";         
        endif;
    }

    $available_size .= '</select>' . "\r\n";

    echo $available_size;
    ?>

<?php
global $_wp_additional_image_sizes;
print '<pre>';
print_r( $_wp_additional_image_sizes );
print '</pre>';