1971. Example of the dose distribution of a two-field treatment with 8 MV photon beams with wedge filters, calculated with the treatment planning software which was developed by the physicist Rob van der Laarse.
At the end of the 60's a cooperation of the physicist Herbert Marcuse and the radiation oncologist Marion Burgers with the company IBM did not result in a usable treatment planning system. In 1971 physicist Rob van der Laarse at the Netherlands Cancer Institute (NKI) writes a computer program for the dose calculation of treatments with external beams. In the following years Van der Laarse further develops his computer program into a full treatment planning system (TPS) for megavolt photon and electron beams and for brachytherapy. This planning software has been used later in the first treatment planning system by the company Nucletron.
Dr. Rob van der Laarse, clinical physicist. Employed by the NKI from 1969 to 1984. Head of the group Physics and Instrumentation of the Radiotherapy Department.
Rob is designer and programmer of software for megavolt therapy with external beams and brachytherapy treatment planning. The planning software is described in his doctoral thesis "Computerized Radiation Treatment Planning" 
Part of a stack of punched cards
Typewriter for punching holes in the punch cards
Initially when the Netherlands Cancer Institute (NKI) was still situated in the Sarphatistraat, the data for the computer calculations were imported with punched paper tape in the large EL-X8 computer (made by the Dutch company Elektrologica) of the Mathematical Computer Center of the University of Amsterdam in the 2nd Boerhavestraat. Later this became a box of punched cards to be imported in the mainframe Control Data Cyber 73 computer of the Amsterdam Foundation for Academic Computing (SARA), situated at that time in a building of the Free University at De Boelenlaan in Amsterdam. From the new NKI at the Plesmanlaan, it was necessary to bring the boxes of punched cards to SARA and then afterwards bring back the printed output.
For the demanding calculations of the NKI, the SARA mainframe computer had to be used. Twice a day the arithmetical instructions were provided and the dose calculations were then directly performed with priority. Later an in- and output station became available in the nearby situated building of ACTA. Between Christmas and New Year the Cyber was normally down, but for these treatment planning tasks an exception was made and the system was made available for a short period of time.
With the purchase of the first CT scanner, a DEC PDP11 computer system became available for the Radiotherapy Department. The treatment planning software was rewritten for this purpose, and from then on calculations were performed "at home".
SARA, Amsterdam Foundation for Academic Computing
Automatic optimisation of the treatment plan. Around 1974 Rob van der Laarse writes a computeroptimisationprogram for treatment planning of megavolt photon beams from a linear accelerator. This development was put forward because only once or twice a day a treatment plan could be calculated, and it required a lot of time to calculate different treatment plans for a patient. Based on the availability of cross sections of the patient, the delineated target area and organs at risk, the computer program automatically generates a treatment plan in which radiation beams, beam directions, field sizes, wedge filters and weight factors are optimized. In 1976 a paper describing this program is published in the British Journal of Radiology.