Magento Add Payment Method to Admin invoice Grid

 protected function _prepareCollection()
    {
        $collection = Mage::getResourceModel($this->_getCollectionClass());
      
        $collection->join(array('payment'=>'sales/order_payment'),'main_table.order_id=parent_id',array('method','po_number'));
      
        $collection->getSelect()->joinLeft('sales_flat_order_address', 'main_table.order_id = sales_flat_order_address.parent_id',array('full_name'=>'CONCAT(sales_flat_order_address.firstname, " " , sales_flat_order_address.lastname)','full_address'=>'CONCAT(sales_flat_order_address.street, " ", sales_flat_order_address.city, sales_flat_order_address.postcode)','telephone','city','firstname','postcode','company','street','email' ) )->where("sales_flat_order_address.address_type =  'billing'");
      
      
          $collection->getSelect()->joinLeft('sales_flat_order', 'main_table.order_id=sales_flat_order.entity_id', array("shipping_desc"=>"shipping_description","weight"=>"weight","subtotal_incl_tax"=>"subtotal_incl_tax","base_subtotal_invoiced"=>"base_subtotal_invoiced","base_shipping_invoiced"=>"base_shipping_invoiced","base_tax_amount"=>"base_tax_amount"));
        
     
         $this->setCollection($collection);
         return Mage_Adminhtml_Block_Widget_Grid::_prepareCollection();
        
    }
$payments = Mage::getModel('payment/config')->getAllMethods();
        $methods = array();
            foreach ($payments as $paymentCode=>$paymentModel)
            {
                $paymentTitle = Mage::getStoreConfig('payment/'.$paymentCode.'/title');
                $methods[$paymentCode] = $paymentTitle;
            }
            $this->addColumnAfter('method', array(
                'header' => Mage::helper('sales')->__('Payment Method'),
                'index' => 'method',
                'filter_index' => 'method',
                'type'  => 'options',
                'width' => '1050px',
                'options' => $methods,
            ));