A servo drive from Control Techniques has given a total body irradiation (TBI) table a new lease of life at the Institute of Oncology Ljubljana in Slovenia, bringing both the required precision and reliability to an advanced life-saving radiotherapy procedure.

The original system was designed and built in 1989 by the maintenance department of the Institute of Oncology Ljubljana, and featured a DC servo drive for the control of the table movements.  However, advances in radiation treatment led to the need for an upgrade to achieve better accuracy and improved reliability.

The Institute chose Control Techniques’ local representatives PS Logatec as their partner in this project and a system was designed around Control Techniques’ new Digitax ST Plus servo drive, providing both the accuracy of control needed and the reliability without the need for an additional PLC.

Total body irradiation (TBI) is a special radio therapeutic technique for the treatment of predominantly hematological diseases such as leukemia’s and lymphomas. The technique is mainly used for conditioning prior to bone marrow transplantation in combination with intensive chemotherapy.  The main objective of TBI is to deliver a uniform dose 12 Gy within ±10% of the prescribed dose to a patient’s whole body and for the reference point the accuracy of the delivered dose must be within +- 3 %, whilst optimally sparing vital organs such as the lungs.  This is difficult to achieve because of the variations in the thickness of the patient’s body and the density of the tissue.

There are several methods of TBI, the system at the Institute of Oncology Ljubljana, uses a table that moves along rails, known as the ‘translation’ method.  Good clinical results encouraged them to invest in an upgrade to give them greater control and reliability – the latter being most critical since the table must not stop or deviate from the set speed cycle whilst the radiation source is on.