Gilles Holst (Haarlem, 20 March 1886 - Waalre, 11 October 1968) was a Dutch physicist and, as of 1914, the first employee and director of the Philips Physics Laboratory (Philips Natuurkundig Laboratorium, "Natlab").
The first radiologists in The Netherlands could only buy their irradiation equipment from Germany or France. No X-ray industry existed in the Netherlands, the Philips company only produced light bulbs. During the First World War (1914-1918) the trade in strategic products such as X-ray tubes and radium was halted and the Dutch radiologists search for a solution for the necessary repairs of the vulnerable primitive machines. In particular, it is through the initiative of the Amsterdam professor and radiologist J.K.A. Wertheim Salomonson that Philips decides to look into the repair and development of X-ray tubes. Wertheim Salomonson knows Anton Philips and is able to convince him to start research into the technology of X-ray tubes at the newly set up Philips Physics Laboratory (1914). Thus, Philips followed competitors like General Electric in the US, which has already carried out much scientific research.
Due to circumstances, also the Netherlands Cancer institute (NKI) gets involved; Wertheim is scientific advisor to the NKI and the brother of Frans Gaarenstroom, radiologist in the NKI, is deputy manager of Philips. It is through these personal relationships that NatLab director Ir. Gilles Holst visits the Radiotherapy Department of Frans Gaarenstroom in December 1917 in order to study x-ray technology and the problems of tubes breaking down.
Thanks to the cooperation of Philips Company Archives, a scan of the original notebook used during Holst's visit is available for study. From this it can be seen how Gaarenstroom used his equipment for therapy and imaging.
The first page of the notes by Gilles Holst, made during his visit to the AVL in December 1917. Courtesy Philips Company Archives.
Based on historical literature, the high voltage can be estimated from the spark arc distance: therapy radiation 26 cm = 110 kV, imaging soft tissues 14 cm = 68 kV, semi hard 16 cm = 75 kV, hard 18 cm = 82 kV. From the notes of Gilles Holst, it appears also that Gaarenstroom used a gas flame to heat the palladium in the glass envelope whenever the hydrogen pressure in the tube became too low. Hydrogen diffuses easily through heated palladium and this process was used to adjust the gas pressure in the tube.
The filament of the Coolidge tube requires a current of 4 to 5 A. Holst reports on the use of the available Crookes tubes and of one Coolidge tube. It would take until 1919 until all radiation units in the NKI-AVL had been refitted with Coolidge tubes.
The origins of Philips Medical Systems / Philips Health Care division. After the visit of Holst to Amsterdam, a start is made in the Philips "NatLab" laboratories with the repair of X-ray tubes. This is the beginning of the Philips X-ray activities that would lead up to the formation of the division Philips Medical Systems. As of 1922, Philips introduces its own X-ray tubes. These are initially improved models of the Crookes tubes as patents of General Electric prevent Philips bringing Coolidge tubes onto the market.
Since that first contact in 1917, the Antoni van Leeuwenhoek hospital has had regular collaboration with the Philips NatLab, Philips Medical Systems and the company Elekta which, in 1997, bought the radiotherapy activities from Philips. Examples on this website are: 1925 - experiments with Metalix X-ray tube, 1936 - irradiation experiments with neutron radiation, 1939 - experimental 1MV X-ray machine, 1973 - prototype of a dual energy linear accelerator, 1975 - experimental neutron therapy, 2001 - Cone Beam CT scanner on the linear accelerator (partnership in the Elekta consortium of contributing customers).