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Case studies

Supporting commissioning of new radiotherapy equipment safely and promptly

Case study

Varian-Linac-NPL-measurements.JPGThe need

The incidence of cancer is rising, but so also is the number of patients who have early detection. Around 30% of cancer patients are treated with radiotherapy and it has proved effective at increasing survival rates and the quality of life for the patient.

A linear accelerator, or Linac, is the most common way to deliver external beam radiation treatments to cancer patients. To ensure that patients have access to the best treatment techniques, the NHS and other radiotherapy providers continuously modernise radiotherapy services, including the replacement and upgrading of Linacs. Ensuring the Linac can target and destroy cancerous cells in a precise area of a patient's body with minimal dose to the surrounding healthy tissue is key to a successful treatment. Measuring the beam data characteristics is necessary to commission a new Linac in a timely and accurate manner. The data is also used by the treatment planning system (TPS) to model the beam and ensure that the correct radiation dose is reliably calculated and safely delivered.

Linac and TPS commissioning processes are complex and time consuming. They require experience and knowledge of the equipment and standards. The high level of detail required can be challenging for junior medical physics trainees and overwhelm clinical physicists who also have clinical priorities.

The solution

NPL has more than 15 years of experience providing dosimetry services including Linac and TPS commissioning. Our team can effectively support decision makers and managers of radiotherapy services considering externally outsourcing the commissioning of newly installed radiotherapy devices.

Our highly qualified staff, including several registered clinical physicists, deliver a service that is based on the development of clinically relevant working practices introduced at NPL Linacs and TPSs, including:

  • Developing and implementing Linac Quality Assurance (QA) procedures.
  • Commissioning of NPL Linacs and TPSs used for the design and development of clinically relevant research.
  • Developing end-to-end QA tests for clinical trials and radiotherapy audits, in collaboration with Radiotherapy Trials Quality Assurance Group (RTTQA) as well as leading international comparisons.

The level of expertise in radiation metrology achieved by NPL researchers working in medical physics applications, have allowed the development of methods and procedures to measure more specific and complex aspects of Linacs and TPSs, including small fields, multileaf collimator (MLC) offset tables and transmissions.

For radiotherapy centres with multiple Linacs, treatment scheduling requires that whenever possible, they are ’matched’ so that they offer very similar radiation characteristics and can be used interchangeably for treatment. This ensures maximum efficiency, covers any breakdown and minimises the risk of interrupted treatment for patients.  In collaboration with end users, we have evaluated specific measurement methods and scan analysis procedures, perfecting a system to ensure high-quality Linac matching.

The NPL team have clinically relevant expertise in treatment planning and audits and add value to the commissioning service through ongoing consultancy agreements.

The impact

Working with NPL enables radiotherapy managers from the NHS and other health treatment providers to speed up their Linac and TPS commissioning process. The experience of the NPL commissioning team will give them confidence that their treatments will be up and running promptly and meet technology, safety and regulatory requirements from the dosimetry point of view. We work with our partners towards an improvement of the patient workflow by facilitating a seamless transition between the installation and the first patient treatment.

We ensure complete transparency while on-site taking measurements, processing and analysing the data and finally when presenting the end user with the full collected data set and validation information. We provide confidence to radiotherapy treatment end users, practitioners and patients.

Radiotherapy centres can also benefit from our service by keeping their medical physicists concentrating on research or clinical priorities, leaving the one-off commissioning tasks to the NPL team. Engaging with the local team is part of our approach which enables us to give them an overview of the commissioning process and provide training which adds to their expertise. It also gives them access to absolute dose verifications and dosimetry audits for newly introduced treatment techniques to be carried out efficiently and effectively.

What the scientist says

We support Linac commissioning for linear accelerators from all manufacturers and TPS commissioning for all commercially available treatment planning systems and algorithms.


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