Dec 21, 2007
The early days of medical physics
This article is an edited version of a presentation by W Alan Jennings at the celebrations of the 10th session of the European School of Medical Physics in Archamps, France, on August 31 2007.
I am happy to participate in these celebrations near Geneva for two reasons. Firstly because my father was the Leagues of Nations and European national correspondent for the News Chronicle (a London-based national newspaper) in the 1920s and 30s. I was born, and spent my childhood, in Geneva. Secondly, I am happy to talk about the early days of hospital physics as I can recall such times first-hand. Indeed, I shall tell the story through personal experience.
If one goes back to the 19th century, there are references to the involvement of physicists in medicine. Michael Faraday, for example, gave lectures to doctors in hospitals. However, it wasn't until 1906 that the first two lecturers were appointed to teach physics to students in UK medical schools.
Outside the medical schools, the main drivers for the establishment of medical physics as a stand-alone discipline were the discovery of X-rays by Wilhelm Roentgen in 1895; the discovery of radioactivity by Henri Becquerel in 1896; and the discovery of radium by Pierre and Marie Curie in 1898. The application of ionizing radiations in medicine created a need for full-time physicists in hospitals, those physicists being primarily concerned with the use of X-rays and radium in radiotherapy and safety measures in radiation protection.
There was an honorary physicist at the Royal Cancer Hospital, London, in 1911, but the first physicist actually appointed to a hospital was Sidney Russ in 1913. Russ secured a position at the Middlesex Hospital, London, having been a research fellow there since 1910. By the time of the Second World War, there were between 35 and 40 such posts in the UK.
How it all began
In those early days, the principal activity of medical physicists was the measurement of X-rays and radioactivity at both radiotherapy and protection levels. Indeed, the UK was pre-eminent in this field. At an organizational level, there were notable advances with the establishment of the International Commission on Radiation Units and Measurements (ICRU) in 1925 and the International Commission on Radiological Protection (ICRP) in 1928 (with the latter preceded by the British X-ray Protection Committee, which was set up in 1921).
The UK's National Physical Laboratory (NPL), a standards/measurement institute established at the turn of the century, also played a pivotal role. The laboratory acquired its first radium standard in 1913, made by Marie Curie and specified in terms of mass. When the roentgen, the unit dosage, was defined in 1928, X-ray standards were set up at NPL to provide calibration services to hospitals, initially for pastilles (a rudimentary system of dose measurement) and later for Victoreens, Hammer, Philips and Siemens dosemeters.
The NPL inspected departments for protection measures, and provided a route for physicists into the profession. Radon plants were also set up around the country to provide an alternative to radium for implants (sealed radon seeds emitted the same radiation but with a much shorter half-life, and thus could be used for permanent implants).
Two pioneers worthy of mention here were Herbert Parker (a physicist) and Ralston Paterson (a radiotherapist) who, in two joint papers in 1934 and 1938, devised the well known distribution rules and dosage tables for brachytherapy. Other well known physicists in the hospital world before the Second World War were Val Mayneord (dosimetry and mathematical analysis), Bill Spiers (dosimetry in bone), Harold Gray (after whom the unit of absorbed dose is named) and Frank Farmer (of the secondary standard dosemeter).
Next, let me turn to the war years and how I came to be involved in hospital physics. After two years studying physics at London University, I was faced with a commitment to do weapons research on completion of my degree. As a Quaker, I could not accept that, and had to leave college and face a government tribunal.
They sent me to Sidney Russ at the Middlesex Hospital. Russ was sympathetic to my views, his wife having founded an organization called "Women against war"; they had also lost a son at the front. In 1942, I met Frank Farmer, who introduced me to radiological physics, at which point I was sent to a place in the countryside called Barton-in-the-Clay. I was working at a radon centre that had been set up in an old lime tunnel to supply radon seeds and related appliances to hospitals during the war. I spent two years working at the centre, while studying at London University at weekends to complete my degree.
During that time, Russ was responsible for two vital services based at the Middlesex Hospital. The first was the "King's Fund" stock of radium, which was issued for use by radiotherapists (though it was not available for some periods during the war). He was also responsible for running the King's Fund Panel of Physicists, which provided physicists to London hospitals where there were no full-time appointments.
Probably the most important step forward in hospital physics during the war was the formation of physicist associations. In May 1943, Bill Spiers, with others, launched the Northern Group of Hospital Physicists (with 11 members). Four months later, Sidney Russ and colleagues launched the Hospital Physicists Association (HPA). The HPA was the first national body of its kind - the American Association of Physicists in Medicine did not follow until 15 years later - and the forerunner of today's Institute of Physics and Engineering in Medicine (IPEM), which now has over 3300 members.
At the time of its launch, the HPA had 53 members. I was based at the radon centre, but was invited to attend the launch. Today, I am one of only four surviving founder members. In 1944, I was transferred to the Middlesex Hospital, where I joined the King's Fund Panel of Physicists. We visited a number of hospitals, usually in pairs, training by apprenticeship on the job - there were no courses in those days. We calibrated X-ray-tube outputs, planned treatments (Parker/Paterson), checked protection, looked for lost radium, etc. We learnt to use the Victoreen dosemeters, taking them to NPL for calibration.
Some of the hospitals had surprisingly primitive set-ups - one still used pastilles for dosage measurements. These comprised platino-cyanide discs, which changed colour from yellow to orange, with the dose assessed by comparing the resulting colour change against a set of reference standards given known doses. The problem was that my colleague and I could not always agree on which colours matched. Another hospital had an X-ray treatment machine in which a lead shutter was operated by pulling an attached string through a hole in the protective lead-lined cubicle at the controls.
After two years working on the panel, I was appointed to one of the hospitals I had been visiting: the Royal Northern Hospital in north London. The post included the teaching of radiological physics to its radiography school, as well as treatment planning in which the physicists participated in seeing patients in the clinics - a practice some of us were to help introduce into American hospitals in the 1950s.
In the 1940s and 50s, many physicists were attached to radiotherapy departments but did not have equal status to their clinical colleagues. There were a few exceptions, and as staff numbers increased, and the range of activities expanded outside radiology, the number of independent physics departments gradually increased.
At this point, I should like to return to the formation of the HPA. Prior to the HPA, hospital physicists had opportunities to meet through membership of the Physical Society and the British Institute of Radiology. The latter was particularly valuable as it was set up as a multidisciplinary society where no distinction was made between professions (doctors, scientists, engineers), an arrangement that still holds good today.
The Physical Society, now the Institute of Physics, did not set up a medical physics branch until much later in the century. However, as I mentioned earlier, in May 1943 the Northern Group of Hospital Physicists was established, followed four months later by the launch of the HPA. These bodies provided a vital service for their members who, apart from a few groups in large centres, were in most cases still working on their own.
Between 1944 and 1968, three residential HPA meetings were held every year, in different locations around the country. The meetings included visits, scientific presentations and business briefings in support of the profession. The HPA functioned essentially as a club, most participants knowing each other. From 1969, however, the pattern changed to one general meeting each year, plus other special meetings on chosen topics. A "diagram and data scheme" was launched for the exchange of information. For example, depth-dose tables or isodose curves for specified radiation beams measured at one centre were made available to others.
In the early years after the launch of the HPA, although the bulk of its increasing membership came from the UK, there were many members from overseas. What's more, a mechanism for formal cooperation between existing national medical physicist associations was established in 1954 with the setting up of the International Organisation for Medical Physics (IOMP), followed in 1978 by the European Federation of Organizations for Medical Physics (EFOMP).
Let me now turn briefly to my experiences of the American scene. In the mid-1950s, I was among a group of UK medical physicists invited to the US to introduce "British practice in hospital physics". I accepted the offer on a one-year exchange basis. My time at the Argonne Cancer Research Hospital in Chicago, IL, was a great experience. Although I was pressed to remain, I found the financial aspects of medical practice there unacceptable, and did not extend my stay.
Unlike the UK National Health Service (NHS), where treatment depended on availability and need, our patients in Chicago received only what they could afford. A case in point: I found myself teaching radiotherapy students how to prepare plans for dynamic treatments with a superb high-activity cobalt unit, only to find the treatment was not delivered, replaced instead by two opposed fields as a cheaper approach. On a broader level, at that time the NHS was viewed by my US colleagues in derogatory terms.
Following my placement in Chicago, I was fortunate to be involved in two innovative research projects at the Royal Northern Hospital. In both cases, the work exemplifies the significant contributions made from a small centre at that time. One project concerned a comprehensive study of the physical characteristics of low-energy X-rays for superficial treatments. This followed the acquisition of the first Matchlett beryllium-window X-ray tube at the International Congress of Radiology in London in 1950.
The second project concerned dynamic radiotherapy. Having established the three existing techniques - conical rotation, rotating chair and arc or pendulum therapy - Anthony Green, the radiotherapist in charge, conceived the idea of tracking the spread of disease along sinuous pathways. This was achieved by the application of arc therapy whilst the patient was moved both laterally and vertically as necessary at the same time as being translated along the axis of rotation. This programme evolved in three stages, reflecting the state of the art at each period, and the concept constitutes a precursor to today's intensity-modulated radiotherapy (IMRT).
For my part, I left the hospital environment in 1967 and transferred to NPL. Initially, I ran the dosimetry service there, but in 1975 was appointed head of the division of radiation sciences and acoustics. At this point, instead of using some of the wide-ranging radiological calibration services, I became responsible for their provision, including the development of new standards and their international comparison. Such standards concerned photons and neutrons - covering a range of energies at protection, therapeutic and industrial levels, entailing ionization, calorimetric and chemical techniques - as well as a number of radionuclides.
The post entailed much national and international representation, a brief that spanned the International Bureau of Weights and Measures, the International Commission on Units and Measurements, and the International Atomic Energy Agency, among others. As a civil servant, however, I had to retire at the age of 60 (in 1983), but for the past 24 years I have continued my involvement in radiation metrology.
Throughout the 20th century and to the present day, medical physics and engineering have extended their reach into many fields of medicine (IPEM, for example, now encompasses 12 special interest groups). From its early days, diagnostic radiology has blossomed into an assortment of powerful, complementary imaging techniques such as CT, MRI, SPECT, PET and ultrasonics. Similarly, radiotherapy has embraced computing technology, leading to conformal therapy by intensity-modulated and image-guided techniques. A colleague of mine summed it up nicely: "Medical physics slipped quietly into medicine and is now really big."
- A supplement of the journal SCOPE, entitled "The Heritage of the Institute of Physics and Engineering in Medicine", provides a comprehensive account of the professional and organizational development of medical physics, not only in the UK but internationally, between 1943-2006. Contact IPEM. Tel: +44 (0)1904 610821.
- Development of physics applied to medicine in the UK over the period 1945-1990. This constitutes a witness seminar, held in July 2005, in which 28 prominent hospital/medical physicists were invited by the Wellcome Trust to take part in a structured discussion of their recollections of the subject as it evolved over the years. This discussion was recorded, transcribed and edited, with the addition of numerous footnotes, references and appendices, and published by the Wellcome Trust.