Magento 1.9 Shopping Cart – How to Display Custom Image Type on Shopping Cart Page

I have created a custom image media type "custom" using this tutorial:

http://www.pixafy.com/blog/2012/12/adding-a-fourth-image-position-to-the-admin-for-a-magento-product/

Currently magento shows thumbnail image type on shopping cart page but I want custom type image on the page.
How can I do this?

I have tried this:

    /magento/app/design/frontend/rwd/default/template/checkout/cart/item/default.phtml

 <img src="<?php echo $this->getProductCustom()->resize(180); ?>" alt="<?php echo $this->escapeHtml($this->getProductName()) ?>" />

after trying Siarhey Uchukhlebau's answer:

<img src="<?php echo $this->helper('catalog/image')->init($_item->getProduct(), 'custom')->resize(180);?>" alt="<?php echo $this->escapeHtml($this->getProductName()) ?>" />

I got this error:

Image file was not found.

Trace:
#0 /var/www/html/magento/app/code/core/Mage/Catalog/Helper/Image.php(166): Mage_Catalog_Model_Product_Image->setBaseFile(NULL)
#1 /var/www/html/magento/app/design/frontend/rwd/default/template/checkout/cart/item/default.phtml(38): Mage_Catalog_Helper_Image->init(Object(Mage_Catalog_Model_Product), 'custom')
#2 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(241): include('/var/www/html/m...')
#3 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/rwd/de...')
#4 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#5 /var/www/html/magento/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#6 /var/www/html/magento/app/code/core/Mage/Checkout/Block/Cart/Abstract.php(174): Mage_Core_Block_Abstract->toHtml()
#7 /var/www/html/magento/app/design/frontend/rwd/default/template/checkout/cart.phtml(147): Mage_Checkout_Block_Cart_Abstract->getItemHtml(Object(Mage_Sales_Model_Quote_Item))
#8 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(241): include('/var/www/html/m...')
#9 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/rwd/de...')
#10 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#11 /var/www/html/magento/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#12 /var/www/html/magento/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
#13 /var/www/html/magento/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Text_List->_toHtml()
#14 /var/www/html/magento/app/code/core/Mage/Core/Block/Abstract.php(637): Mage_Core_Block_Abstract->toHtml()
#15 /var/www/html/magento/app/code/core/Mage/Core/Block/Abstract.php(581): Mage_Core_Block_Abstract->_getChildHtml('content', true)
#16 /var/www/html/magento/app/design/frontend/rwd/default/template/page/1column.phtml(55): Mage_Core_Block_Abstract->getChildHtml('content')
#17 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(241): include('/var/www/html/m...')
#18 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/rwd/de...')
#19 /var/www/html/magento/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
#20 /var/www/html/magento/app/code/core/Mage/Core/Block/Abstract.php(919): Mage_Core_Block_Template->_toHtml()
#21 /var/www/html/magento/app/code/core/Mage/Core/Model/Layout.php(555): Mage_Core_Block_Abstract->toHtml()
#22 /var/www/html/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
#23 /var/www/html/magento/app/code/core/Mage/Checkout/controllers/CartController.php(181): Mage_Core_Controller_Varien_Action->renderLayout()
#24 /var/www/html/magento/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Checkout_CartController->indexAction()
#25 /var/www/html/magento/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('index')
#26 /var/www/html/magento/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#27 /var/www/html/magento/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#28 /var/www/html/magento/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#29 /var/www/html/magento/index.php(83): Mage::run('', 'store')
#30 {main}

after this I set up place holder image for this custom attribute from this path:

System -> Configuration -> Catalog -> Product Image Placeholders

and now I am getting the place holder image but not the actual image that I selected as "custom"