Dr Geraldine McCarthy, a rheumatologist, was pregnant with her third child and chatting to a colleague at the Medical College of Wisconsin, in Milwaukee. She was about to have one of those inspirational moments that turn an ordinary doctor and scientist into a leading light of the medical world.
It was August 1997. The US army had invited submissions for breast-cancer-research grants. McCarthy's colleague had heard the army was looking for proposals from people who didn't ordinarily research cancer. They wanted people who "think outside the box" said the colleague as McCarthy's brain began to whir.
The college is a centre of excellence for rheumatology, a broad area that deals with arthritis, fibromyalgia, lupus, vasculitis and kidney, liver and blood problems - a host of illnesses to do with inflammation.
By serendipity, as McCarthy puts it, she had found herself in an ideal setting for research, with a mentor, Daniel McCarty, who was a pioneering rheumatologist and, like his protΘgΘe, an enquiring, outside-the-box person.
McCarthy's research passion was calcium crystals, a subject medicine had ignored. The conventional view was that the crystals were innocent bystanders. Nobody had looked into them deeply. Even the textbooks were slim on the subject.
Being an outside-the-box person, McCarthy had long suspected that there was much more to be learned about calcification, the process in which calcium crystals develop in a joint, causing osteoarthritis.
Calcium, or hydroxyapatite, crystals are found in most osteoarthritic joints, and act as a fertiliser does towards a plant. Ordinary joint cells start to multiply until the joint lining becomes thick. The thickened lining produces enzymes that dissolve the cartilage in the joint.
It is this overgrowth of the lining that contributes to the inflammation, pain and swelling that osteoarthritis sufferers - about 50 per cent of everyone over 65 - are only too familiar with.
In cancer, cells also multiply out of control and spread through the body, facilitated by enzyme secretion. It occurred to McCarthy that there were striking similarities between the response to crystals of the cells in an arthritic joint and the behaviour of cancer cells. Crystalisation in osteoarthritis is not cancer, however.
McCarthy also knew that a woman's milk ducts calcify during the development of certain types of breast tumour. As calcification produces enzymes, calcium crystals in the breasts could be encouraging tumours. It was already known that one type of breast microcalcification was associated with poorer prognoses.
"A little light bulb went on over my head," says McCarthy. She submitted a proposal to the army, which liked the fact that her idea was so unusual. A few months later, she received a research fellowship worth £500,000.
Her moment of inspiration in a corridor in Milwaukee had made her the first medical researcher to identify a possible relationship between calcification and breast cancer. A previous paper, published in the high-impact Journal Of Biological Chemistry, had helped to seal her status as a big player in medical research.
McCarthy is a classic wild goose. She grew up in Portlaoise, was a boarder at Mount Anville, then studied medicine at University College, Dublin. Like many Irish doctors, after qualifying she worked for a while in hospitals in the Republic, meeting her husband, Dermot Kenny, at the Richmond, in Dublin.
Then the couple joined the US medical circuit. Settling in Milwaukee, the couple had three children in a family-friendly working environment, with medical colleagues who were a joy to work with.
For 11 years, it was a good life. Like hundreds of talented medical people in the 1980s and 1990s, they felt fortunate to be able to gain experience and contacts abroad. "There were no job prospects then, and I think we are a small country, and you need to go away and bring something back," says McCarthy.
Home calls you. So when Kenny, a cardiologist, got the opportunity to head the clinical research centre at the Royal College of Surgeons in Ireland, he took it. McCarthy followed. She spent her first year back nurturing her research programme, then joined Mater-Misericordiae Hospital as a consultant rheumatologist.
Her research into crystals and breast cancer is now based at the college, in Dublin, where a group of researchers is investigating crystalisation and its effects. McCarthy has herself become a mentor for a high-powered team.
The Wellcome Trust is supporting the research, and the US army has given one of McCarthy's team, Dr Maria Morgan, a further £150,000. The Dublin-based Health Research Board had also offered Morgan funding, but when the army also offered, she decided to release the board's money for other projects.
Enterprise Ireland has also paid for Morgan to go to Milwaukee, to learn how to do the experiments that may help the team understand why the crystals form in the breast in the first place. "This makes Dublin a crystal centre of the world," says McCarthy, who recently chaired a scientific meeting of the American College of Rheumatology, in San Francisco.
There is nothing you can do to prevent yourself developing the crystals, she says. All we know is that cartilage is capable of producing them and that, in some cases, there appears to be a genetic component. That we know so little about a potentially important subject is why McCarthy's research is so badly needed.
There is a lifetime of research ahead for the team at the Royal College of Surgeons. As well as breast cancer, crystals may have a role to play in heart disease. Heart attacks are caused by the narrowing of arteries - or atherosclerosis - followed by build-ups of sticky platelets (components of the blood that promote clotting).
When crystals develop in an artery, they can produce enzymes that break through the lining of the blood vessel and thicken it, as in an arthritic joint. This thickened area is rough, so it catches platelets and forms a blockage.
McCarthy's story is inspiring not least because medical research is only one aspect of her life. She sees patients every day, and clinical work takes up most of her time. Describing her colleagues at the Mater as outstanding, she says the secret of her success is working with great teams and never taking on too much.
She runs five kilometres every other day, reads voraciously and usually manages to be home in time for dinner with the family. The couple spend weekends with their children, who are aged 13, 10 and five. It's a lifestyle she thinks wouldn't have been possible in the US, where parents seem to spend all their time taxiing their children from one activity to the next.
McCarthy's life has the foundation of a happy marriage. Her eldest daughter said recently: "You and Dad are partners." And that's what they are. "He knows my issues and I know his. We're both into medical research, so we spark off each other," says McCarthy. "He even cooks a few nights a week."