The last of the conventional simulators, a historical overview.

Simulator Varian Acuity.jpg 

This Acuity simulator was installed in 2006 by the manufacturer Varian. In 2012 this last conventional simulator in the Netherlands Cancer Institute (NKI) had not been in use for some time and it was decided to sell it. In the NKI and elsewhere the modern tools in the preparation of radiation treatment are based on 3D imaging in the CT-scanner and the use of virtual simulation techniques on computer screens.

Historical overview of the conventional simulators that have been in use in the Netherlands Cancer Institute (NKI).

For almost 40 years, the conventional simulator has been an indispensable instrument in the design of an irradiation plan for the individual patient.

RRTI simulator 1974.bmp.jpg 

1972, the RRTI simulator. In the Radiotherapy Institute of Rotterdam (RRTI) in the Netherlands, head radiation therapist Els van Doornum and physicist Hans van de Poel devise the characteristics of an X-ray machine that can simulate geometrically the irradiation with a linear accelerator.

By means of a diagnostic X-ray tube a radiation beam with the dimensions and direction of the planned treatment beam is aimed at the patient. The faint image of the X-rays that are attenuated by the body of the patient is captured and amplified with an X-ray image intensifier (here of the manufacturer Oude Delft, later known as Old Delft). The resulting fluoroscopy image is displayed on a TV monitor in the control room. Under fluoroscopy the projection of the planned radiotherapy treatment  is adjusted and evaluated on the TV screen. Finally a radiograph is made to check the result. Marks are made on the skin of the patient to assist the setting up on the treatment machine using light pointers. 

Elsewhere in the world similar ideas are being worked out, but manufacturers are still unable to deliver a suitable machine. In The Netherlands, physicist Hans van de Poel and instrument maker Mr Florisson in the RRTI in Rotterdam are the first to construct a number of machines for their institute and one for the NKI. The latter is in use from 1972 up to about 1985.  

1973 simulator toshiba.jpg 

1973, the second simulator is a Toshiba. The Japanese manufacturer is chosen because they also sell a transversal X-ray tomography machine at a favourable price. This "Tomograph" is placed in the same room and shares the same treatment table with the simulator. One expects to make transversal images with this machine that can be used in the design of a treatment plan. In practice the  image quality is disappointing. Usefull cross section images will appear later with the CT scanner, but in the early '70s the CT-scanner is still under development however and will not appear until 1979 in the NKI. From then on CT images are used in dose planning, next to the vital use of the conventional simulator in the geometric design of the treatment. 

Simulator 11 Philips.jpg 

1981, Philips LocSim. One of the first Philips simulators replaces the Toshiba machine in the NKI. Philips with its British subsidiary MEL is an important producer of linear accelerators for radiotherapy (In 1997 this activity is sold to Elekta).  When a demand for simulators arises, Philips Medical Systems in Best, the Netherlands, designs this Localiser/Simulator, the LocSim. At the request of the NKI the optical rangefinder is added and instead of one pendant, fixed control panels are fitted to either side of the table.  

Philips LocSim V2a.jpg 


Around 1985, Philips LocSim V2.   The old RRTI simulator is replaced by a newer version of the Philips LocSim. The 9" image intensifier-TV camera combination has been replaced by a 14" system, which offers more overview of the area to be irradiated. Independent setting of each of the four field edges brings the simulator up to date with the latest innovation in the linear accelerator. The settings of the simulator are displayed on screens and can be read out by a computer. This last option is not utilized yet.


Simulator ABB 2 kl.jpg 

1988, ABB Dynaray TS. The NKI now has three simulators available. This new machine has been developed during 1987 and 1988 by the Asea Brown Boveri (ABB) Company in Switzerland. Technical specialist Henk van der Gugten was closely involved in the design. The machine in the NKI is one of the two prototypes and the Dynaray TS is one of the most accurate simulators ever designed. Accuracy is especially important for a simulator as irradiation set-ups are determined that are repeated for weeks on the linear accelerators. A deviation in the simulator thus has effect on all treatments and will result in a systematic error.  


Ximatron Simulator example2.jpg 

1995, Varian Ximatron. The oldest Philips LocSim is replaced by this machine. The Varian Company has bought the radiotherapy division from ABB in the early nineties and kept its own Ximatron as only simulator. This machine is also more accurate than the Philips LocSim. A new feature is that the X-ray fluoroscopy image is captured by a digital video camera. The digital images of the simulator can be used directly for treatment planning and simulation, no photographic film is needed. The introduction of "film free" simulation proceeds slowly. 


1999 GE LXi.jpg 

1999, General Electric CT-scanner, type LXi. The second Philips LocSim is replaced by a single slice General Electric (GE) CT-scanner. This scanner is placed in the old simulator room and is used primarily to make scans for virtual simulation in the preparation of radiotherapy. With the CT-scanner two workstations with virtual simulation software of GE are purchased. This introduces virtual simulation in the  planning of the radiation treatment. 


CT sim imaging.JPG 

2004, Siemens CT-scanner, type Sensation Open. An ultra-modern CT-scanner is installed in a newly built scanner room. The Sensation Open is a fast 16-slice helical scanner. The aperture of the scanner has a diameter of 82 cm. The machine is equipped with respiration triggering ("respiratory gating") which allows taking account of organ movements in the treatment plan. At the same time that the scanner room is built, the neighbouring unit of treatment preparation is extended and equipped with 25 workstations of the new Philips Pinnacle treatment planning system.  With the images from the new scanner the advanced irradiation techniques on the new generation of image-guided linear accelerators can de virtually simulated and the dose distributions computed. The conventional simulator no longer plays a role in this.  

Simulator Varian Acuity.jpg

2006, Varian simulator type Acuity. The Radiotherapy Department decides that in the coming years for part of the treatments a conventional simulator is still needed. This machine is also to be used in the training of radiotherapists and radiation oncologists to acquire three-dimensional insight.

The ABB simulator from 1988 is therefore replaced by a Varian type Acuity in 2006. In this machine technology has been developed to a high degree of perfection. The quality of the X-ray photography and fluoroscopy is improved by digital image processing. The image detector is a thin amorphous Silicon flat panel, mounted on a robot arm that provides a great degree of freedom for set up around the examination couch.  The machine is entirely computer-controlled and the control offers many possibilities for computer-assisted set-up. Radiotherapists that are used to the older machines experience the control as awkward. This is the last simulator in the NKI-AVL. 

In 2008 a second Siemens Sensation Open CT-scanner is taken into use and the old Varian simulator type Ximatron (1995) is dismantled. In 2012 the decision is made to sell the last conventional simulator, the Acuity. In the preparation of modern, automated image-guided radiotherapy, the conventional simulator has become redundant.