What methods can be used to check the isocenter of a clinical linac?

The isocenter of a linear accelerator (linac) is a crucial point where the radiation beams converge, and verifying its accuracy is essential for effective treatment delivery. Multiple methods can be employed to ensure the isocenter is correctly aligned, each contributing unique advantages.

Optical methods involve utilizing visual alignment tools such as laser beams, which can help healthcare professionals accurately pinpoint the isocenter. This approach provides real-time feedback on the positioning of the treatment apparatus and confirms that the linac is calibrated properly to the intended treatment location.

Mechanical methods include the use of physical tools and fixtures to assess alignment. This can include the application of alignment bars, check tables, and other physical devices that confirm the mechanical components of the linac are in proper position relative to the isocenter. These methods ensure the integrity of the linac's structure in addition to its functional correctness.

Radiation methods involve the use of dosimeters or other radiation detection equipment to measure the radiation output at different angles and confirm that the dose distribution matches expectations at the isocenter. These measurements provide a quantitative analysis of the radiation delivered and are essential for verifying that the treatment plan is being followed accurately.

Each of these methods can be used independently or in combination, which underscores the importance