Yes, you can use any True Type font. I made a Captcha module that renders the characters using fonts from a TTF I uploaded and referenced.
I simply uploaded the arial.ttf file from my Windows XP machine to my website and it worked just fine.
Here is a code snippet from the file that does it:
var $font = 'arial.ttf';
$textbox = imagettfbbox($font_size, 0, $this->font, $code) or die('Error in imagettfbbox function');
$x = ($width - $textbox)/2;
$y = ($height - $textbox)/2;
imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code) or die('Error in imagettftext function');