The ACDS Level III onsite audit determines dose delivered to selected points in an anthropomorphic phantom. This is an end-to-end audit where the phantom undergoes all steps within the radiotherapy planning and treatment pathway. Dosimetry measurements are made using Farmer type and CC13 ionisation chambers, microDiamond detectors and Gafchromic™ film. 

Standard Level III audits include: 

  • 3DCRT
  • IMRT
  • VMAT
  • SABR

Cranial SRS and adaptive RT Level III audits are also available.

Cranial SRS

The cranial SRS audit is performed using a customised IMT MAX-HD™ Phantom, allowing for optional detectors, film placement inserts and MR visible material. It is compatible with Conventional Linacs, HyperArc, Gamma Knife®, CyberKnife®, Halcyon™ and TomoTherapy® systems. The detectors used are Gafchromic™ XD and EBT3 Film and PTW 60019 microDiamond point dose detectors.

The audit consists of five cases ranging from simple output measurements, a single SRS target, and multi-metastases treatments. A four-lesion multi-met case tests the geometric accuracy of targets visible on MRI only. A five-lesion multi-met case tests the performance of the SRS delivery system in very complex deliveries and is based on the TROG ASM 2017 competition dataset.


Head-shaped object with electrical components lying face up on a table

Online adaptive

This initial adaptive audit is offered as an extension of the standard Level III audit. Performed using the ACDS modified CIRS thorax audit phantom, it is designed for the Elekta Unity MR-Linac and Varian Ethos™ online adaptive radiotherapy systems. The central solid water IMRT insert for the thorax phantom is replaced with a water-filled replica for MR image matching and dose measurement.

Two new audit cases are introduced, testing the currently available adaptive radiotherapy workflows to treat the C-Series IMRT/VMAT tumour volume. The Elekta Unity’s adapt-to-position workflow is tested by adapting the standard C-Series plan to treat the same volume in a physically offset phantom. The case to test the Ethos’ AI-driven adaption and Unity’s adapt-to-shape workflows takes an initial plan based on a modified C-Series volume and generates an adapted plan to treat the standard C-Series volume. These adaptive audit cases use virtual targets that are provided in the planning structure set.

Further developments, such as adaption to a CT/MR visible tumour and MR-only planning, will be available in the motion adaptive audit.

Motion management and adaptive audits – In development

The ACDS has been developing a new Level III audit for respiratory motion management techniques. A new phantom has been designed to allow facilities to apply their clinical workflows for simulation, planning, image guidance and treatment for both passive and active motion management techniques, applied to two stereotactic body radiation therapy (SBRT) sites – lung and liver. This is achieved by providing targets which move periodically in the superior-inferior direction to simulate internal respiratory motion, coupled with an external platform that moves in the anterior-posterior direction. This enables the use of technologies essential to motion management, such as respiratory-correlated imaging (e.g. – 4DCT/CBCT) and gating using external monitoring devices.

Our new CIRS motion phantom will form the basis for the next generation of ACDS Level III audits incorporating motion management, online adaption and MR-only planning with realistic anatomical inserts. Currently in early stages of design and development, the new audit cases will be applicable to kV and MR imaging and all available 4D radiotherapy delivery systems. The phantom will be customised to enable specific audit capabilities and will be known as LOLA (Live On Line Adaption).

We’re looking forward to bringing you updates on our exciting research, as it develops.

Respiratory motion management phantom
Figure 1: Respiratory motion management phantom
Phantom with see-through components on table
Figure 2: Live On Line Adaption (LOLA) phantom

Datasets for download (last updated September 2022)

* Ensure download for the correct fusion dataset, corresponding with phantom that was scanned at your facility (Red or Yellow)

ACDS audit level III documentation


Access to information FOI disclosure log Information public scheme