In 1950, Dr Henri Lokkerbol takes part in the 6th International Conference on Radiology in London (chaired by Ralston Paterson). At the technical exhibition, Mr. W. Grey, a sales manager for Philips England, explains to him the development of the 4MV linear accelerator. Still in the experimental phase, it will take a few years before it becomes available for clinical purposes.
In the 1950's, it was still not clear whether a Cobalt machine or a linear accelerator should be acquired for megavolt therapy. Accelerators are still in an experimental phase and it will be years before these become clinically available. In 1955, the Netherlands Cancer Institute and the radiotherapy institute of Rotterdam (RRTI) both decide to purchase a large Cobalt machine for megavolt therapy.
Great Britain takes the lead in Radiotherapy. During the 1950's in England, there was competition within the industry to develop the first linear electron accelerator for the treatment of cancer. This was stimulated by the government which saw the need for modernisation in this area.
In 1953, one of the first 4 MV linear accelerators, developed by Philips-Mullard, was installed in a hospital in Newcastle upon Tyne, England.
An educational film was made in the 1950's about the first 4 MeV Philips-Mullard accelerator. Note: the film lasts over 11 min. It provides an explanation for those interested in early linear accelerator technology. Click on the link: Principles and use of the Mullard linear accelerator
The portal, on which the accelerator and the head of the radiation machine are mounted, rotates on two floor supports. The English construction name for this portal is 'Gantry'. The rotating part of the modern medical linear accelerator is still often called 'Gantry', even though it usually has a different construction form.
In 1953, another vendor, Vickers Metropolitan, Manchester also installed their first 4 MV linear accelerator, the 'Orthotron', at the Christie Hospital with Prof. Paterson. See photo left.
Both the Philips and the Vickers machines of 1953 could only rotate isocentrically over about +/- 110 degrees. This could be increased slightly by allowing parts of the floor to be moved away.
The Betatron. A newspaper article from 1955 described that the Christie Hospital in Manchester also had a Betatron with an energy of 20 MeV at their disposal .
The photo shows Siemens equipment at the Technical exhibition of the 6th ICR, in London in 1950. Siemens equipment was, in many ways, much further developed than their competitors *see note below.
On the right of the stand is a small Betatron. This is a compact megavolt circular electron accelerator, which was developed in 1944 by Siemens. It was designed for the medical use of electron beams. The energy of the model shown here is six million electron volts. In later models this was increased to 15 and 20 MeV. In 1955, the Christie Hospital in Manchester had a Betatron at their disposal.
On the left of the stand, is an X-ray convergence machine, which used a skin sparing irradiation technique. Dr. Henri Lokkerbol bought this machine in 1953. This will be discussed later in the timeline.
In the 1950's and 1960's, betatrons with energies for photon and electron beams up to 45 MeV were the most powerful machines. Comparatively rich institutes in Scandinavian countries, Switzerland, England and the USA acquired these machines. Brown Boveri & Co. (BBC) in Switzerland provided 78 units; other vendors are Siemens in Germany and Allis Chalmers in the USA. There is little interest for these machines in the Netherlands. This is probably due to the expense, and the clinical and physical complications with the still unknown high energies. In The Netherlands, conventional X-ray machines were still in use. These were able to perform rotating treatments. Finally a national agreement to start using cobalt machines for megavolt therapy was reached.
* In 1950, Rolf Wiederoe, the Norwegian constructor and inventor of particle accelerators worked on the protoype of a 31 MeV betatron for Brown Boveri (BBC) in Switzerland. In his biography, Wiederoe writes that the machine on display in London, that was described above, was an empty shell, without an accelerating tube. Siemens still wrestled with technical problems for 15 and 20 MeV in the betatrons. At that time BBC already had a functioning prototype of a 31 MeV Betatron. This was being finalised with megavolt electron and photon beams for the Kantonsspital in Zurich.