TrueBeam is a linear accelerator made by Varian that delivers external beam radiation therapy to treat cancer. It combines real-time imaging, precise beam shaping, and motion tracking to target tumors with submillimeter accuracy while limiting radiation exposure to surrounding healthy tissue. The system is used across a wide range of cancer types, including tumors in the brain, lungs, liver, spine, prostate, breast, and gastrointestinal tract.
How TrueBeam Delivers Radiation
The TrueBeam system rotates around you on an arm called a gantry, delivering radiation from nearly any angle. Inside the machine, tiny metal plates called “leaves” move independently to sculpt the radiation beam so it matches the three-dimensional shape of your tumor. These leaves can shift and reshape during treatment, adapting the beam as it targets the tumor from different positions. This allows clinicians to concentrate the dose on cancerous tissue and pull it away from nearby organs.
Real-time imaging is built directly into the delivery process. Before and during each session, the system captures images of the tumor so the treatment team can verify its position. This matters because tumors can shift slightly between sessions due to normal body changes like bladder filling or weight fluctuation. It also matters within a single session for tumors that move with breathing, like those in the lungs or liver.
Treatment Techniques It Supports
TrueBeam isn’t a single treatment method. It’s a platform that supports several advanced radiation techniques, each suited to different clinical situations:
- Intensity-modulated radiotherapy (IMRT): Shapes the radiation dose in three dimensions to conform tightly around the tumor, useful when a tumor sits close to sensitive structures.
- Image-guided radiotherapy (IGRT): Uses built-in imaging to verify tumor position immediately before delivery, improving targeting accuracy.
- Stereotactic body radiotherapy (SBRT): Delivers very high doses in a small number of sessions (often one to five), typically for small, well-defined tumors in the lung, liver, or spine.
- RapidArc (volumetric modulated arc therapy): Delivers a precisely sculpted dose in a single 360-degree rotation of the gantry, significantly shortening treatment time compared to older fixed-angle approaches.
The system also supports gated delivery, which synchronizes the radiation beam with your breathing cycle. For a lung tumor that moves as you inhale and exhale, the machine fires only when the tumor is in a specific position. Combining gated delivery with the high-intensity mode, TrueBeam can complete a full lung SBRT fraction in roughly seven minutes.
Brain Tumor Treatment With HyperArc
For patients with brain metastases, TrueBeam offers a specialized planning and delivery technique called HyperArc. This is a form of stereotactic radiosurgery (SRS) designed to treat one or multiple brain tumors in a single session using a single setup point. The system automatically determines the best combination of gantry angles, table rotations, and beam directions to cover every target while minimizing radiation to healthy brain tissue between lesions.
HyperArc automates much of the treatment planning workflow. It calculates beam paths that avoid physical collisions with the patient or the treatment table, and it uses built-in optimization tools to keep the radiation dose between separate tumor targets below a set threshold, typically around 17 percent of the prescribed dose. The goal is to treat all targets to at least 98 percent of the prescription dose while keeping the low-dose “spillover” between them as small as possible.
What a Treatment Session Feels Like
A typical TrueBeam session, from the moment you’re positioned on the table to the end of delivery, takes about 10 to 15 minutes. The actual radiation delivery within that window is often shorter. With certain high-dose-rate techniques, the beam-on time for an IMRT session can be as brief as three to four minutes.
You lie on a flat treatment table in a comfortable position, usually face up. The machine is open-topped, meaning there’s no enclosed tube like an MRI scanner. A rotating arm moves around you, but it doesn’t touch you. You won’t feel the radiation itself. The process is painless during the session, though side effects from the cumulative dose may develop over the course of a multi-session treatment plan.
How TrueBeam Compares to Older Systems
Older linear accelerators delivered radiation effectively, but they lacked the integrated imaging and rapid beam-shaping that TrueBeam provides in a single platform. The practical differences for patients come down to a few key areas. Sessions tend to be shorter because the system can modulate the beam continuously while rotating, rather than stopping at fixed angles. Imaging and treatment happen on the same machine without repositioning, reducing the chance of targeting errors. And the leaf system reshapes the beam faster and with finer resolution, allowing clinicians to treat tumors near critical structures, like the spinal cord or optic nerves, with tighter margins.
These capabilities have made TrueBeam particularly useful for cancers that were historically difficult to treat with radiation, including pancreatic tumors surrounded by sensitive organs and tumors near the spine where even small dose errors could cause nerve damage. The submillimeter accuracy of the imaging system gives clinicians enough confidence to use smaller safety margins around the tumor, which means less healthy tissue receives radiation and side effects can be reduced.