A unique collaboration

Validating a transmission detector on Varian linacs by Görgen Nilsson, CTO and founder of ScandiDos

After several years of collaboration with Varian we are very proud to have completed a validation of the use of a Delta⁴ Discover system on various linacs from Varian.

In the past, 3^rd party MLC and other equipment were used on linacs in general without the kind of validation that is now required by the IEC to ensure the safe use of linacs combined with 3^rd party systems. The project included an interoperability agreement where the project was specified including which linac version to be included etc. Next an R&H (Risk and Hazard) analysis was made in a group with people covering the various areas of knowledge from both Varian and ScandiDos ensuring that nothing was left behind or forgotten. The goal was to make the use of the Delta⁴Discover system safe on the linac system and not jeopardize any of the Varian safety controls etc. and also to ensure that the workflow isn’t affected in a negative way. A Delta⁴ Discover system was made available to Varian for a year to make any testing on it including attenuation of the beam. One conclusion was that the effect on depth doses and profiles were less than measurement accuracy and thereby no re-commissioning of the beam data used in the TPS is necessary. Recommissioning of the beam data is a major task as all medical physicists know. Additionally, it is a risk to require two sets of beam-data one with and one without the transmission detector in place, the Delta⁴ Discover only requires one set of beam data.

The Delta⁴ Discover has a small attenuation that is recommended for correction. It is preferable to be created as a block tray factor in the TPS. The R&H indicated a possible miss match in applying such a factor and thereby it was decided that the Delta⁴ Discover should have a unique accessory code. Thereby, whenever the Delta⁴ Discover device is attached to the treatment head the accessory code will be seen in the R&V system and it must correlate with the selections in the plan.

The project was a major effort but we are very happy to now provide customers with a seamless QA solution to the Varian TrueBeam and Clinac machines, a vital step in the verification process during treatment.

Görgen Nilsson,
Founder and CTO ScandiDos AB