The "Dosimulator" in use after moving to the new building of the Netherlands Cancer Institute in Amsterdam-Slotervaart in 1973. The radiation therapist is Truus Borghuis.
The Dosimulator has been designed to help in choosing quickly a good irradiation technique from many possible solutions.The final dose planning is calculated on a digital computer.
In 1971 the use of a digital computer for dose calculations is still in its early phase. It is also time consuming. For a calculation the input has to be created on punch cards. The computer is situated in the Amsterdam Foundation for Academic Computing SARA, and the calculations are performed during the night.
In 1971 the clinical physicist Herbert Marcuse from the NKI-AVL completed his doctorate with a thesis entitled: "Light as analogon for dose; a "Dosimulator" for radiotherapy". Part of his doctorate research is the construction of a device that makes the dose distribution in a patient visible using the blackening of a film and images on a TV screen..
A film has been made showing the use of the Dosimulator in the preparations for a treatment. In the summary of the Dosimulator Film the device is demonstrated, while it also shows the radiotherapy department with a linear accelerator in 1972.
summary of the Dosimulator Film. click the arrow to run the film.
The principle of applying blackening of a photographic film to simulate a dose distribution has been described around 1920 by Dr. Hans Hohlfelder. He positioned already processed films on top of each other on a light box. Herbert Marcuse realized with modern techniques an application of this principle.
The iso-light lines on the monitor coincide with the dose distribution calculated with a digital computer.
The Dosimulator, nicknamed by colleagues the "Marcusograph", contains film on which the dose distribution of a large variety of irradiation fields, varying in sizes and angle of incidence, have been exposed. The beam images have been assembled on long strips of slide film format. Four slide projectors have been provided with a motorized slide holder in which such a slide strip is loaded. On the control console it was possible to install a combination of 1-4 different radiation fields that could be projected simultaneously on a TV camera. In the combined light image the lines and surfaces with the same light intensity, the isolumen, are made visible. During film processing the isolumen lines have been made equal to isodose lines. The isolumen lines were projected over a cross section of the patient to simulate the irradiation. However, in practice dose simulation in this way was unreliable due to the instability of the system, in particular of the video technique.The Dosimulator was taken out of practice in 1976.
Four film projectors project light in a mirror system on a TV camera.