Display a Matrix field block entry when the block's entry exists
Try replacing

{% for asset in block.imageField %}
    &lt;img src="{{asset.getUrl}}" alt="{{ asset.title }}" /&gt;
{% endfor %}


with

{% set asset = block.imageField.first() %}
&lt;img src="{{asset.getUrl}}" alt="{{ asset.title }}" /&gt;


If you're using Craft 3, replace .first() with .one()