Varian Linear Accelerator Base Frame Removal

Every linac vault has a base frame. How do you remove a linear accelerator base frame?

A History of Base Frames

In the 90’s and early 2000’s, most Varian linear accelerators installed globally included a base frame that consisted of a 36” diameter turntable. The industry referred to them as the “standard base frame”. As Varian introduced more advanced linac models into the market, the company developed a newer base frame that was slightly broader called the “VEO base frame”. The VEO base frame’s design consists of a larger 52” diameter turntable and weighs an estimated 2260 pounds (1025kg).

Base Frame Removal Process

Base frames can be removed and re-purposed for future use. However, preserving a base frame requires a careful process that demands attentiveness. The following steps by qualified professionals can be taken to properly remove and save a base frame from a Varian linear accelerator:

1. Ensure that there is good ventilation in the room, blocking off any vents to prevent dust damage, and creating negative air-flow in the room. Air scrubbers are also a good idea
2. Take thorough measurements of the pit
3. Use a diamond edge saw to cut around the perimeter of the base frame
4. Punch holes around the perimeter, filling the newly punctured holes with expansion concrete
5. Use jackhammers to remove concrete in the appropriate areas
6. Clear the rubble
7. Utilize an A-Frame to remove the base frame, tub, and turntable
8. Fill the pit with concrete or modify the pit for its new base frame

Varian linear accelerator models using the VEO base frame include: Clinac 21EX, Clinac 2100CD, Clinac 23EX, Clinac 2300CD, iX, Trilogy, and TrueBeam. It is often recommended that VEO base frames be replaced with new ones when purchasing a linac. Although, in most cases, the existing one can be used.

Universal Base Frames

There is also a third category of base frames – the universal base frame. Universal base frames can accommodate both a low-energy and high-energy linear accelerator. They are the same size as the HE VEO base frame, with just slight modifications. This includes a longer support plate that is closer to ISO (Isocenter), allowing for a low-energy linac to be placed on it. Therefore, when using the universal with a low energy machine, the vault must be large enough to accommodate it.

If you want further insights into base frame or linear accelerator equipment removals, please contact ROS and we can assist you with any questions and concerns you may have.