National Physical Laboratory

Clinical linac beam data acquisition

Clinical linac beam

Linac commissioning is a time-consuming process. NPL offers support in the form of staff time, equipment and expertise to assist in the beam data acquisition part of the commissioning process. NPL would acquire measurements with treatment planning system (TPS) modelling purposes, but also with TPS model verification intentions.

NPL can provide:

  • Its own measurement equipment: 3D water phantoms and associated software
  • Various types of detectors:
    • Cylindrical and plane parallel ionisation chambers
    • Small volume ionisation chambers for measurements in small fields
    • Stereotactic, electron, and photon diodes are also available
  • Secondary standard electrometers for relative output measurements
  • One/two members of staff on-site for two to four weeks, as required
  • The possibility for two NPL teams working simultaneously in two different linacs at the same institution
  • In the case of mobile linacs or low-energy and medium-energy X-ray equipment, the possibility to perform the beam data acquisition process at NPL premises
  • If required, NPL personnel can support the local specialists by setting the square, rectangular and shaped fields necessary for modelling and verification that are not part of the standard settings in linac consoles

NPL personnel are capable of working with most of the 3D water phantom solutions available. Therefore, if convenient, all the beam data acquisition work could be performed by NPL using the local measurement system and detectors.

Typical data for X-rays and electron beams will be acquired according to the TPS requirements and/or on measurements list requirements previously agreed with local specialists. Independently of the scanning solution used, NPL will create the relevant queues for the tasks involved. Generally, acquired data will include:

  • Profiles and ionisation and depth dose
  • Square, rectangular and asymmetric, open and wedged fields
  • Output factor measurements, including small fields
  • Dose point measurements in conditions different from reference

Photon and electron independent verification audits are also available prior to release of a machine for clinical use.


Customer Services tel: +44 20 8943 8695

Last Updated: 8 Jan 2018
Created: 28 Nov 2011


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