The new EU directive and its implementation

In 2013, a new directive (2013/59/Euratom) was formed that establishes uniform basic safety standards for the protection of the health of individuals subject to occupational, medical and public exposures to ionizing radiation against the dangers arising from such exposure. The directive shall be transformed into domestic law in the member countries in Europe before 15th of January 2018 and new equipment purchased after 6th of February 2018 must follow the new rules. 

To fulfil the directive, several of the countries in Europe e.g. Sweden and France have updated either the national rules or recommendations in the beginning of June. The question we are going to focus on is the interpretation of one of the more important sentences in the new directive (page 27, paragraph 3b)

Member States shall ensure that:

equipment used for external beam radiotherapy with a nominal beam energy exceeding 1 MeV to has a device to verify key treatment parameters. Equipment installed prior to 6 February 2018 may be exempted from this requirement.

This part is for example taken into the Swedish radiation protection law SSM2016-1358 as

all utrustning som används för extern strålterapi och som har en nominell energi som överstiger 1 megavolt, ska vara försedd med en anordning för kontroll av relevanta behandlingsparametrar

Google translate:

all equipment used for external beam radiation therapy and which has a nominal energy greater than 1 megavolt, shall be fitted with a device for checking the relevant treatment parameters.

The question is thereby what does this mean? So let’s look into the various part of it:

  • First; we talk radiation therapy and energies above 1MeV
  • “Fitted with a device” or “has a device” indicate that this is done with an independent method or equipment. If it is an independent method the raw data must also fulfil the independency criteria.
  • Verify: Nowadays it is often forgotten what verify means and then it is good to go back and look at the synonyms:  Verify or Prove or Validate or Substantiate or…. It simply means to ensure the correctness. In our case it is the correctness of delivered treatment or the right radiation dose at the right place.
  • The right dose could refer to either the prescribed dose or the planned dose.
    • The first step - to ensure that the prescribed dose is also the planned dose can be verified using a secondary dose calculation software.
    • The second step - to verify that the planned dose is also the delivered dose -  requires that all relevant parameters are independently verified.
      • In the last almost two decades it has been popular to verify that the planed dose is also the delivered dose using Pre Treatment Verification. In the last decade the technology has mainly been 3D phantoms containing detectors. The benefit with this technique is that it verifies all relevant parameters at the same time. The drawback is that the method is time consuming and that it can’t be done during treatment of the patient.
      • Lately Logfiles has been used and the information in those files has been quantified as dose via calculations of the relative intensity, MLC positions etc. This is however NOT a verification because it fails on the first instance, independence.
      • It is also popular to use EPID images and back-project the information into the patient and calculate the dose inside the patient. This is a somewhat independent solution, depending what criteria one have for independency. However the fact that all EPIDs are reading the image information in sequences makes it impossible to know the synchronisation between the acquired data and gantry angle, MLC position, output etc. and thereby the correctness of it. The EPID solution doesn’t have any independent information on gantry angle and even if an independent inclinometer was used it would still not be synchronized with the EPID read-out. The combination of EPID and logfiles doesn’t help to get a complete and independent solution.
      • Transmission detectors have the potential to fulfil the requirements in the new EU directive because of independency and a benefit is the possibility to get a fast and efficient implementation of the solution
      • Transmission detector solely do not however fulfil the requirement - the key treatment parameters. Gantry- and collimator angle is missing and if it is measured it has to be synchronized with time resolved fluency measurement to be useful. For the transmission detector to also verify the MLC-leafs, the configuration of the detectors is crucial. Additionally if the intension is to verify the leaf motions during dynamic treatments the verification must be done in real-time or at least once per control-point.

Our conclusion of the above analysis of the EU directive from 2013 is that a transmission detector like the Delta4 Discover including gantry and collimator angle verification, synchronisation and MLC position verification fulfils the new requirements and is available for clinical use today.