The new Dynaray TS therapy simulator of the company Asea Brown Boveri (ABB) in the simulator room in the extended radiotherapy department (1988). Photograph Coen van der Gugten.
This simulator was designed by ABB in Switzerland in 1987-1988. The machine in the NKI is one of two prototypes. Technical specialist Henk van der Gugten was closely involved in the design of this accurate machine.
Conformation therapy and high dose-high precision radiotherapy techniques demand a high degree of accuracy with which the radiation beams can be directed onto the patient. Older radiotherapy machines fail to equal this accuracy through loose mechanical construction and instability together with inaccurate position read out. In later years, the research group at the NKI develops solutions to compensate for inaccuracies in the irradiation settings through clever retrieval of measurement data from automatic portal image analysis. This was not yet possible in 1988 and for this reason much attention is given to the stability and accuracy of the treatment table and radiation machine.
The Dynaray TS is one of the most accurate simulators ever constructed. Accuracy is of extra importance in a simulator, on which irradiation settings are determined which will be repeated daily for weeks at a time on the linear accelerators. A mistake in the simulation affects all the treatments. Older simulators are often less accurate than the accelerators which they are supposed to simulate. The ABB Dynaray TS is designed to be better than the accelerators. The isocentre of this machine lies within 0.8 mm and the movements and positioning are of high precision and are computer controlled. Settings can be pre-programmed.
The table top has a low density and allows X-ray imaging from all sides. Thanks to strengthening by composite fibres, it has a pliability which is just as small as the pliability of an accelerator table which is reinforced by steel bars. The diaphragm system is equipped with the independently adjustable diaphragms and field wires X1, X2 and Y1 and Y2, which have just previously been introduced in the new accelerators. This allows the simulation of asymmetrical irradiation fields over a large area.
ABB also delivers a 4 MV linear accelerator which is installed in treatment room 8 (since then removed, at the position of the present passage to the B hall). This machine is also of high quality, stable mechanical construction and can be very accurately operated.
Both the accelerator and the simulator of ABB are equipped with a robust industrial computer system by Brown Boveri. All functions and movements of the machines are carried out and registered in a fail-safe mechanism. Settings are controlled by at least two independent sensors. The radiation data of the patient are registered in an electronic treatment chart and the settings of accelerator and treatment table can be automatically executed. The radiation therapist has control over this and has to be in the treatment room for the movements to be executed. A conventional setting by hand is also possible.
On the publicity picture, an ABB-NKI electronic portal image detector is being positioned.
The NKI megavolt image detector made available as industrial product.An agreement is signed with ABB for the industrial production and sale of the Electronic Portal Imaging Device (EPID) which has been developed in the NKI. In close cooperation with Van Herk and De Gans, the circuitry of the EPID is produced as industrial modules and translated into an integrated circuit on an electronic chip.
The ABB prototype of the megavolt portal image detector according to NKI design, with a fluid-filled ionisation chamber matrix of 256x256.
a - Industrially produced EPID circuitry. b - Complete EPID cassette, not much larger than a film cassette. c - EPID cassette fixed to a robot arm of Varian. The positioning and retracting of the cassette is motorised and can be operated remotely.
Merger and shut down of industrial activities BBC Radiotherapy division. During the 1980's, the Swiss industrial concern Brown Boveri Company expanded its radiotherapy activities. This led to a collaboration agreement with the Netherlands Cancer Institute (NKI). New linear accelerators and a simulator were designed. The revolutionary EPID, developed in the NKI became the basis for the Portal Vision system with which BBC was able to take on the competition. In 1988, BBC merged with Asea from Sweden and became Asea Brown Boveri (ABB). During the consolidation of the new company, the small radiotherapy department was sold to market leader Varian in the USA.
Robot arm for the EPID. Under the Varian flag, the development of the NKI EPID practicle clinical tool was continued. A robotic arm is designed with which the cassette can be positioned in the radiation beam and retracted to a parking position flat against the gantry. This robotic support is designed to be mounted onto a Varian accelerator. The setting range of this robot arm is too small for this to be fitted to the larger accelerators of Philips/Elekta and BBC in the NKI. Due to the practical advantages of working with the EPID on a motorised arm, the NKI chooses to adapt the design of the robot arm itself. With generous cooperation from Varian Switzerland, technical specialist Henk van der Gugten, together with a team of technical students and the NKI instrument makers realises an adapted robot arm. See more on this in item "Development robot arm for EPID cassette" in 1997.