From the earliest X-rays to the latest body scanners, the ability to visualise the inside of the living body has revolutionised medical diagnosis. With a profound understanding of physics, great technical ingenuity and a mission to put these skills to use in the service of medicine, John Mallard, who has died aged 94, was one of the first to establish routine scanning services that revealed tumours in organs such as the brain and the liver. His team at the University of Aberdeen built the first whole-body MRI (magnetic resonance imaging) scanner and produced the first clinically significant MRI images of a hospital patient.
Mallard was interested in ends rather than means and pioneered several different forms of imaging technology, adopting another technique each time it offered the chance to produce clearer images or greater safety for the patient. In the beginning, locating tumours or other pathology involved injecting radioactive tracers and picking up their emissions with detectors outside the body.
Scientists in the US developed the principle of tomography (essentially 3D imaging) in 1964, rotating detectors around the body to build an image in successive slices – a process that Mallard likened to the slivers that emerged from the bacon slicer in his father’s shop. From 1967 to 1969, he led the development of the Aberdeen Section Scanner, a machine that used this principle to detect gamma rays emitted by injected radioisotopes and produce a digital output that could guide radiotherapy in cancer treatment.
In 1964 Mallard had shown that there were differences between normal and tumour tissues in intrinsic signals known as electron spin resonance, and predicted that a scanner based on that principle would be able to “see” tumours without having to inject any radioactivity. No one paid any attention to his paper in the journal Nature, but a few years later scientists in the US made the first research breakthroughs with MRI. Immediately grasping its potential, Mallard hired Jim Hutchison and Bill Edelstein to explore this new approach, which involved detecting the impact of a strong magnetic field on the hydrogen nuclei of the water molecules in living tissue.
As soon as they produced their first successful image of a mouse, Mallard set about raising the funds to build a scanner that could take a human patient. Equipped with the first electromagnet produced by the then fledgling company Oxford Instruments, and using standard copper tubing and second-hand parts, the “homemade” scanner initially encountered a problem with the movement caused by heartbeats, which blurred the image. Hutchison and Edelstein solved this problem, a discovery that Mallard called “the real breakthrough” for MRI. Meanwhile the biologist on the team, Meg Foster, developed a greater understanding of the differences in MRI signals between normal and diseased tissue.
In August 1980, the team’s Mark 1 scanner successfully imaged a cancer patient and revealed previously undiagnosed tumours. The Aberdeen group’s patents on refinements to MRI technology later earned millions in royalties for the university, as commercial manufacturers began to produce scanners for hospitals around the world.
Mallard was born in Kingsthorpe, a suburb of Northampton. His father, also John, ran a grocer’s shop, supported by his wife, Margaret (nee Huckle). John was their only child, and from early childhood was, in his own words, “seriously handicapped by deafness”. In spite of this he won a scholarship to attend Northampton Town and County grammar school. A further borough scholarship took him to the University of Nottingham to study physics.
He stayed at Nottingham for a PhD on the magnetic properties of uranium. In 1951 he began his first job, as a hospital physicist at the Liverpool Radium Institute, where he learned how to inject patients with radioactive iodine and move a Geiger counter across the neck to produce an image of the thyroid gland.
In 1953 he moved to become a senior physicist and later head of department at the Royal Postgraduate Medical School, then based at Hammersmith hospital, in west London. There he built an automatic scanner to detect emissions from injected radioisotopes and print the results, a machine that could reveal brain tumours with an accuracy of 80%.
At Hammersmith hospital he met Fiona Lawrance, who was working as a medical secretary, and they were married in 1958. They had two children, John and Katriona.
In 1965 the family moved over 500 miles north when Mallard took up the new chair in medical physics at the University of Aberdeen – coincidentally it was Fiona’s home town. While there he campaigned to raise the funds to open a PET (positron emission tomography) facility, which eventually opened in the early 1980s.
David Lurie, now professor of biomedical physics at Aberdeen, joined Mallard’s MRI group in 1983. Acknowledging the communication difficulties caused by his “old school” boss’s profound hearing loss, he says Mallard often issued directions to his staff in the form of hand-written memos. “One of his real talents was realising what would become important and putting teams together to investigate these things,” he said, adding that Mallard was fundamentally kind, and delighted when his suggestions proved fruitful.
Mallard retired in 1992, when he was also made OBE. He continued to give talks and write review papers, and devoted his leisure time to gardening, music, opera and ballet, and making jewellery.
Though the Aberdeen team was not recognised in the 2003 Nobel prize for the development of MRI, Mallard received numerous other honours, including the Royal Society Wellcome prize and gold medal, the Royal Medal of the Royal Society of Edinburgh, and the freedoms of the city of Aberdeen and of his birthplace, Northampton. The John Mallard Scottish PET Centre, a purpose-built successor to the one he first established in the 80s, was opened in 1998.
Fiona died in 2020. John is survived by their children and four grandchildren.