In 1969 Dr Jamie Ambrose, who has died aged 82, was the consultant radiologist at Atkinson Morley's hospital in Wimbledon, the busiest centre for neurosurgery in London, where his job was to provide images of the soft tissue of the brain. The task was inherently difficult because the techniques at his disposal - x-rays and injecting substances that were opaque on x-ray into the spinal cord or into one of the neck arteries - were invasive, sometimes traumatic, and of limited efficacy.
Ambrose was developing better, less invasive methods of imaging the living brain. These included pulsed ultrasound, echo encephalography, and injecting radioactive materials whose course could be plotted with a gamma camera.
One morning he received a phone call from Dr Evan Lennon, a radiologist at the Department of Health. Would he see a man called Godfrey Hounsfield (obituary, August 19 2004), who claimed he had developed a revolutionary method of using x-rays to image the brain? Lennon had previously approached another radiologist, who had dismissed Hounsfield as a crank.
Along with the hospital physicist, John Perry, Ambrose had a frustrating interview with Hounsfield, who was wary of explaining how his scanner worked, and would only repeat that it would be sensitive to small variations in tissue density. Hounsfield worked for EMI, a large company that made music recording equipment and also did some defence work, but did not dabble in anything medical.
Eventually Ambrose and Perry took Hounsfield round the department, showing him x-rays, arteriograms, radioisotope scans, and their newest and best ultrasound images. Hounsfield said: "I can do better than that." Ambrose gave him a bottled specimen of a brain cut through and showing a tumour. This suited Hounsfield, who could work on it without giving anything away.
Five weeks later, Hounsfield came back with a Polaroid of the brain showing the tumour, and the haemorrhages within it. He had had to build a larger apparatus to scan the bottle; his prototype had scanned only small pieces of plastic.
When Ambrose saw it he was electrified. The scan showed the tumour clearly, and even areas of bleeding within the tumour. He realised that the world of diagnostic radiology would never be the same again. The techniques that he had learned and developed would rapidly become extinct.
On Ambrose's recommendation, the Department of Health funded EMI's continuing research costs and the building of a prototype scanner. During late 1969 and early 1970 they tested and modified the system, which required a computer that was very powerful by the standards of the time. In August 1970 they carried out the first CT (computerised tomography) scan, on a patient with a tumour on the left frontal lobe.
They ignored EMI's request to show the scanner at a US conference, and unveiled it at a meeting of the British Institute of Radiology on April 19 1972. Following that, Ambrose calculated that they would get better contrast if the patient was injected with a small amount of an iodine compound, and so it proved.
It fell to Ambrose to spread the word internationally, which he did as a scientist and clinician and not as a salesman. He was, in his colleagues' opinion, "pathologically modest" about his contribution. While Hounsfield received international acclaim, a knighthood and the 1979 Nobel prize, Ambrose received smaller tributes - the 1974 Barclay prize from the British Institute of Radiology, the 1977 prize of the European Society of Radiologists, and the 1992 gold medal of the Royal College of Radiologists. Colleagues felt he deserved more.
Ambrose was born in Pretoria, South Africa, the son of an accountant. Barely 16, he volunteered for service on the day the second world war broke out. Refused because of his age, he studied engineering and reapplied on his 18th birthday. He trained as a pilot in the South African air force and flew Spitfires in the Middle East and Mediterranean war zones.
He was demobbed in 1945 and studied medicine at Cape Town university. After qualifying in 1952 and a year's experience in Durban he came to the UK. Following spells at a hospital in Plymouth, the Middlesex hospital in London, and Guy's, in 1958 he moved to St George's and Atkinson Morley's hospitals, and was made consultant radiologist in 1962. He remained there for the rest of his career, retiring in 1988.
Ambrose was an equable, patient and good humoured man who never raised his voice in anger. If he had not been a radiologist he would have been a horticulturist, hybridising plants; that was how he spent much of his time in retirement in Argyllshire. He also painted and loved all aspects of natural history. He leaves a wife and two children.
· James Abraham Edward Ambrose, radiologist, born April 5 1923; died March 12 2006
