Brain scan for Tia the jack russell

Tia is a 7 year old Jack russell, I have had her since she was a puppy and she has been suffering lately with head tremors and this has now lead to her collapsing and losing her balance and having panic attacks, her vet is certain that the casue of this is a brain tumour and she needs a ct scan which costs £1043, her insurannce will not cover it as it was classed as a preexisitng condition as she has been having panic attacks for a while and was on diazapam at one point. I do not work due to ill health and the pdsa are not able to give ct scans. 
Tia is my whole life , I live alone have no children and she is my reason for living and i have to do everything i can in the hope i can help her live as long as I can. she is such a special dog and my heart is breaking that she may be in pain and i cannot afford to help her.