An Ottawa mother is leading the fight to help families get their children access to a critical diagnostic test.

Misty Giroux says a provincial government decision to deny her son access to a PET scan could have cost him his life.

"This was the only way for us to know whether or not this boy needed to have chemotherapy or not," she told CTV News.

When Ben Giroux was 12 years old, he contracted a virus that attacked his heart. Within weeks, he needed to have a heart transplant.

But the anti-rejection drugs Giroux had to take to keep his new heart healthy, also came with a risk -- six months after his transplant, Giroux was diagnosed with non-Hodgkins Lymphoma.

Now, two years later, Giroux remains positive.

"It might sound weird, but I think it's only made me stronger," he said.

Although a CAT scan done at a Toronto hospital indicated Giroux's cancer was gone, his Ottawa oncologist wasn't convinced.

She applied to a program funded by the Ontario government to order a PET scan for Giroux -- a test that can determine where there's cancer and whether or not it is spreading.

The Ontario Ministry of Health denied the request of Ben's oncologist and told his doctor there wasn't evidence to support his lymphoma diagnosis.

"Everything that Ben's gone through, including a transplant, he's probably approaching a million dollar kid and to argue in this particular instance about $1-2,000 didn't seem to make a lot of sense to me," Dr. Karen Mandel told CTV News.

When Mendel got the news from the Ministry, she decided to fight the decision. The Giroux's, however, decided they couldn't wait for the decision to be overturned and paid $2,500 for Ben to have a private PET scan.

The test results showed that Ben still had cancer.

"I do believe that he wouldn't be here today, if we hadn't spent the $2,500," said his mother. "If we didn't do this then we would basically have been sitting on a time bomb."

Ontario has more PET scan machines than any other province, yet the province pays for fewer PET scans than Quebec and Alberta.

"The issue is, how effective are they and are they of real net benefit to Ontarians," said Ontario Premier Dalton McGuinty.

But Ben Giroux says he knows just how effective those scans are.

"Without having these kinds of scans, it could mean, it could literally mean the difference between life and death,' he said.

With a report from CTV's Joanne Schnurr