Varian TrueBeam

A linear accelerator accelerates electrons along a waveguide and directs them at a target, producing a beam of high-energy photons, or uses the electron beam directly for superficial treatment. TrueBeam mounts this on a rotating gantry with a multileaf collimator, a set of computer-controlled leaves that shape the beam field many times a second. Around it sits the imaging equipment: a kilovoltage source and detector for planar images and cone beam computed tomography, and a megavoltage imager that sees the treatment beam itself. A machine can also be equipped with optical surface tracking that monitors the patient's outline in real time and with a robotic couch that positions the patient with six degrees of freedom, correcting rotations as well as shifts; both are options rather than baseline components. The control system links imaging, couch, gantry, collimator and dose rate so that they operate together within one delivery. TrueBeam STx is not a different or later generation: it is the radiosurgery configuration of this same platform, adding a high-definition collimator with finer leaves and the radiosurgery package, and it is catalogued here as a separate node.

Treatment is planned first on a dedicated computed tomography scan, with magnetic resonance or positron emission tomography images fused in where they define the target better. The physics team designs the beam arrangement and the dose, and the plan is verified by measurement before the first session. On each treatment day the patient lies in the same immobilisation device used for planning. An image is taken on the couch and compared with the plan, and the robotic couch corrects the position automatically. During delivery, rotational arc therapy turns the gantry around the patient while the collimator leaves move and the dose rate varies continuously, so the high dose region conforms closely to the shape of the tumour and falls away sharply outside it. For a target that moves with breathing, the system either gates the beam so that it is only on during a chosen part of the breathing cycle, or treats during a held breath, monitored by surface tracking. Nothing is felt during the beam delivery.

The platform treats the full range of cancers managed with external radiotherapy: breast, lung, prostate, head and neck, gastrointestinal, gynaecological, brain and central nervous system tumours, lymphoma, sarcoma and paediatric cases, as well as painful bone metastases and other palliative indications. It supports curative treatment given alone or alongside chemotherapy or surgery, and hypofractionated courses in which a higher dose is given in fewer visits. Its stereotactic capability suits small brain metastases, early lung cancers in patients unfit for surgery, spinal metastases and oligometastatic disease, where a very high dose is delivered in one to five sessions with steep dose fall-off. Motion management particularly helps left-sided breast cancer, where a deep inspiration breath-hold moves the heart away from the chest wall, and tumours of the lung and upper abdomen that move with breathing. A radiation oncologist decides the technique, the dose and the number of sessions.

For patients, the practical benefits are shorter time on the couch, daily verification that the target is in the right place, and treatment plans that keep dose away from healthy organs. Sessions are painless and the patient is alone in the room but watched on camera and in audio contact throughout. A typical visit takes about 10 to 20 minutes, most of which is positioning and imaging. Side effects depend entirely on the region treated and the dose rather than on the machine: skin changes, tiredness, and site-specific effects such as swallowing discomfort, bowel or bladder irritation, are managed by the team as the course progresses. Courses range from a single session for some stereotactic and palliative treatments to several weeks of daily weekday visits for conventional regimens. For those travelling for treatment, the length of the course is the main planning consideration, since attendance must be continuous, and the department will state the number of sessions in advance.