Development of the Selectron afterloader and the start of the company Nucletron

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In 1978 the prototype Selectron-LDR (low dose rate) of the company Nucletron is put into use in the Netherlands Cancer Institute (NKI).

Using this automatic afterloader for the  treatment by means of radioactive sources makes the   internal irradiation  much more relaxed and safer for the patient, physician and nursing staff. 

Until the mid 70's little has changed in 50 years of using the technique of inserting needles with radioactive material in a patient for an internal radiation treatment (brachytherapy). The physician uses simple manual tools to insert the radioactive radium needles into the tissue. Both the physician and the assisting personnel inevitably receive a certain amount of radiation during this procedure. This technique is applied for the treatment of tumours that can be reached through body cavities such as mouth or nose, anus and cervix, and intraoperatively.   

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Special forceps used to place radium needles into a patient, with examples of the position of the needle.

The increasing awareness of the danger of professional exposure to ionising radiation, results in 1975 in the decision to acquire so-called afterloading equipment. During such a treatment procedure a transport channel is first installed from the source container to the area to be treated in the patient. The radioactive source is then quickly transported from the container to the patient and vice versa under remote control. 

In 1975, devices already exist that avoid manual manipulation of radioactive sources. The sources are automatically transferred from a shielded storage into the patient. The purchasing team of the NKI, physicist Harm Meertens and technical engineer Theo Wilmering, are asked to judge the available devices. Their conclusion is devastating; they are badly constructed and unreliable.

A young graduated engineer from the Technical University in Delft, Eric van 't Hooft, shares their opinion and offers to build a device that will fulfill their expectations. His design will be based on the use of modern technology and an Intel industrial processor for digital control.  


A design sketch used to convince the NKI to order the automatic afterloader which was to be designed by Eric van 't hooft.

The company Nucletron is created by Van 't Hooft as a commercial basis for the development of the afterloader. Van 't Hooft builds the first machine in the garage near his house. In the NKI some doubts arise about the successful completion of the project. An agreement is made that all designs and parts will be brought to the NKI after a certain time period. If necessary the construction of the device will then be finished by the group of instrument makers, physisists and engineers in the Netherlands Cancer Institute. In 1978, with some delay Eric van 't Hooft and his team manage to deliver an impressive afterloading device. The Selectron LDR is born and the company Nucletron is developing successfully. 


Eric van 't Hooft with his Selectron LDR.

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The Selectron afterloader has been built around a shielded container in which radioactive cesium spheres are stored. The device also contains non-active spheres. For a treatment, an array of active and non-active spheres is brought into the patient through narrow tubes, by means of air flow. Several channels are simultaneously active. For a gynecological treatment generally 3 channels are used. 

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X-ray picture of a patient with a gynecological applicator, which is loaded with cesium spheres. On the picture the resulting dose distribution of this treatment has been projected as determined with the computer program developed by the physicist Rob van der Laarse.     

In a dedicated treatment room the applicator is positioned precisely in the planned treatment area. The patient is then brought to a shielded room in the hospital and connected to the Selectron. 

After the staff has left the room and the door has been locked, the device is switched on remotely. The radioactive sources are then brought into the patient. When the door of the room is opened, the sources return automatically to the safety container of the Selectron. In this way the nursing staff, the physician or visitors can enter the room without danger. It is no longer necessary to isolate the patient for the time of the treatment, which often takes twenty-four hours or longer. The processor of the Selectron registers the total irradiation time and finishes the treatment automatically when the programmed time has been reached.