Magento PDF发票：如何防止总计部分的翻译

I'd like to find out how to omit the translation part when Magento prints a PDF invoice. The totals section include, Subtotal, Total, Discount, etc. I'm not interested in having these translated in the locale folder, as these terms are already used on other parts of the website front-end, and I want to always print the invoice in plain English.

print_r($total);
$total->setOrder($order)->setSource($source);
if ($total->canDisplay()) {
    foreach ($total->getTotalsForDisplay() as $totalData) {
        print_r($total);
        ....
    }
}

I think I found the code that tells Magento to translate the terms.

print_r($total);

Mage_Tax_Model_Sales_Pdf_Subtotal Object
(
    [_data:protected] => Array
        (
            [@] => Array
                (
                    [translate] => title
                )

            [title] => Subtotal
            [source_field] => subtotal
            [font_size] => 7
            [display_zero] => 1
            [sort_order] => 100
            [model] => Mage_Tax_Model_Sales_Pdf_Subtotal Object
 *RECURSION*
        )

    [_hasDataChanges:protected] => 1
    [_origData:protected] => 
    [_idFieldName:protected] => 
    [_isDeleted:protected] => 
    [_oldFieldsMap:protected] => Array
        (
        )

    [_syncFieldsMap:protected] => Array
        (
        )

)


print_r($total);

Array
(
    [amount] => US$11.99
    [label] => 소계:    // translated term
    [font_size] => 7
)

I tried doing $total['@'] = array('translate'=>''), but it still translates "Subtotal" to another language. Any ideas?