LINACbased

Linac-based describes systems or procedures that rely on a linear accelerator to generate therapeutic particle beams. In medicine, linac-based radiotherapy uses high-energy photons or electrons produced by a medical linear accelerator to treat malignant tumors. In research, linac-based beams serve in accelerator physics and imaging.

The core is a linear accelerator powered by RF cavities, accelerating electrons along an evacuated tube. The beam exits through a gantry-mounted head; shaping devices like multi-leaf collimators sculpt the dose; imaging sequences provide alignment and verification, often with cone-beam CT or portal imaging. Modern systems include MR-Linac which integrates MRI for soft-tissue guidance.

Linac-based radiotherapy enables external beam therapies such as IMRT, VMAT, SBRT, and palliative treatments. It can employ photons (megavoltage X-rays) or electrons for superficial tumors. Treatment planning combines CT imaging with dose calculations to maximize tumor dose while sparing organs at risk.

Advantages include precise dose distribution, conformality, and non-invasive delivery. Limitations include high capital and maintenance costs, need for specialized facilities, patient movement, and extensive QA requirements.

Since the 1950s-60s, linacs have become the workhorse of external beam radiotherapy, with energies typically 4-18 MV photons and electron beams up to 20-25 MeV. Ongoing developments include image guidance, adaptive planning, and integration with MRI. In research, linacs contribute to particle physics experiments and novel imaging modalities.