Sure. Basically you need to understand what you are getting in the response and what you need.
To begin with you are getting a big string in your response for the value of node "LoginResult". Now out of this BIG string, you are trying to capture a substring ("SessionID":"c121d901-22dc-40ec-8562-4aefaccc893b","UserID":"aa819828-78b1-4007-96d4-49113fdf5ef6")
Unfortunately, the only way to do is this through groovy scripting. You can create a groovy script after your test request, read the value of session id and use basic string - substring function to get session id and use it as per your needs.
Regards,
Deepesh Jain