There’s no indication in the documentation that this is possible. Your twig files already have access to {{site.config.*}}, though. Plugins like Import and Header by Taxonomy can inject page headers.
If you can explain more about your use case, maybe we can help you find another way to accomplish it? You can always file an issue as well. Maybe it’s something the developers can accommodate.
You could try replacing the single quotes around title-image by double quotes so page.media['title_image'] becomes page.media["title_image"], in order not to confuse the parser.
Is title_image the full filename of your image or does it have a filename extension such as .png? If so you need to specify page.media["title_image.png"].
You still have the problem with the internal quotes. You still need to alternate single and double quotes. There are numerous online YAML validators. Try copying your header into one of those and make sure your YAML is valid.
Btw, I noticed that in frontmatter, it looks like page.media[image.jpg].url(true) does not output the absolute url of the image, I had to force it with