Imagen redondeada sin cambiar el tamaño / recortar / estirar

http://jsfiddle.net/k7fpz8be/

<div class="circleImage">
    <span class="helper"></span><img src="https://placehold.it/350x150" alt"logo" title="landscape" />
</div>
<br />
<div class="circleImage">
    <span class="helper"></span><img src="https://placehold.it/350x350" alt"logo" title="square" />
</div>
<br />
<div class="circleImage">
    <span class="helper"></span><img src="https://placehold.it/150x350" alt"logo" title="portrait" />
</div>


.circleImage {
    height: 100px;      /* equals max image height */
    width: 100px;
    border: 1px solid grey;
    white-space: nowrap;
    border-radius:50px;
    text-align: center;
    overflow:hidden;
}

.helper {
    display: inline-block;
    height: 100%;
    vertical-align: middle;
}

.circleImage img {
    vertical-align: middle;
    max-height: 100%;
    max-width: 100%;
}

Esto debería funcionar