Jayden Stone knows something is up.
The two-year-old's attention is diverted from playing with a toy dinosaur.
Suddenly, wearing a crestfallen expression, his big brown eyes widen as he senses that something unpleasant is about to occur.
He regards oncology nurse Mariann Cashin with suspicion as she deftly infuses a cocktail of drugs into Jayden's permanent line.
"Funny feeling," he says, betraying an unfortunate familiarity with the debilitating side effects of the drug protocol he has endured since his diagnosis of an atypical teratoid rhabdoid tumour in his brain.
The nurse smoothly deflects the funny feeling with calm words and reassurances and soon Jayden has regained interest in the toy.
Three weeks ago, Jayden's parents Leisl and Danny Stone moved their young family from East Fremantle to the eastern suburbs of Chicago to pursue proton beam therapy for Jayden.
Brain surgery had removed most of the tumour but further treatment was necessary to halt growth of the aggressive cancer.
Radiation therapy was recommended but the Stones held grave concerns about the damage the side effects of regular X-ray radiation therapy could cause to healthy brain tissue in a growing brain, leading them to seek alternatives.
"We were warned that Jayden would not be able to graduate from high school, his cognitive abilities would affect his ability to process information, he would need hearing aids and his eyes could also be affected," Mrs Stone said.
"He had gone through so much with brain surgery and then a bout of meningitis, we couldn't bear to think he might have his personality altered. It's his quality of life and we have to give it our best shot."
A friend's suggestion led them to the ProCure treatment centre in Chicago, a $165 million centre that features its own cyclotron sub-atomic particle accelerator.
The main advantage of proton therapy is the precision with which protons can be deposited into a tumour at a finite depth with little spillage into healthy tissue.
This allows more effective higher doses to be used on a tumour, with fewer side effects.
As the anaesthetic begins to take effect, a drowsy Jayden is wheeled into the treatment room, but there are tears as he recognises the machinery and snuggles closer to seek comfort from his mother.
Anaesthetist Andrew Roth sedates Jayden to prepare him for the proton machine, something he will do every weekday for the next six weeks.
Precise positioning of the tumour is essential for successful targeting and for a child as young as Jayden there is simply no alternative to sedation.
As Mrs Stone leaves the room, radiology technicians move in quickly to fit Jayden with a custom-made Kevlar mask to position his head.
The proton beam machine is impressive but thoroughly intimidating. It has a bed mounted on a gantry dwarfed by a two-storey, 100-tonne rotating wheel that allows proton beams to be directed from every angle.
Technicians and doctors clear the room and head for the control room to monitor Jayden on a host of instruments.
Twenty minutes later, Jayden lies sleeping on a bed in the small recovery room as Ms Cashin flushes his intravenous line and Mrs Stone hovers.
The wall behind him is decorated with the 20 or so handprints of children who have been successfully treated at the Procure centre and are now cancer-free.
Within five minutes he is awake and cuddling his mother and in 10 minutes he has managed to secure himself a treat from the lolly dish in the lobby.
Mrs Stone is effusive in her praise of Jayden's Chicago carers. "Its hard being away from family and friends, there's no doubt about that, but we're surrounded by such positive medical staff," she said.
"Everyone we've met has been so comforting and warm, and say all the right things. They've just been so beautiful.
"It was so worth the journey, without a shadow of doubt."
Like most medical procedures in the US system, the cost of the treatment is staggering. There won't be much change out of $235,000 and Mrs Stone is not sure where the money is coming from.
Fundraising got the family to Chicago and Mrs Stone hopes the State Government will kick in.
But for now her only wish is to see her son's handprint on the cancer survivor's wall.
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