Magento - Get all Cart Product's Categories

Here is the following Code to Get all Product Categories related with Cart :
Use Checkout Session :

$session = Mage::getSingleton('checkout/session');
foreach($session->getQuote()->getAllItems() as $item):
     $_product = Mage::getModel('catalog/product')->loadByAttribute('sku', $item->getSku());
     $cartProductCatId = $_product->getCategoryIds();
endforeach;