How to retrieve a value via get_option when the option_value is stored in a multi-dimensional array?

$term_id = get_query_var('cat'); // the current category ID

$my_fields = get_option('my_category_fields_option');
echo $my_fields[$term_id]['my_title']; // the title corresponding to the current category

(assuming you’re talking about Any examples of adding custom fields to the category editor?)