Improving radiotherapy through Medical Physics developments

It is vital to consider whether the original radiotherapy Quality Assurance paradigms remain appropriate for new technologies, techniques, and priorities as well as resource availability argued Nicolene Coetzee at recent ICON academic meeting.

The topic of improving radiotherapy through Medical Physics developments was presented at a recent ICON academic meeting, where Nicolene Coetzee discussed the new findings in Medical Physics research and development, which is essential to improving radiotherapy (RT) planning and delivery.

The presentation spoke to a clear need for innovative, efficient and effective Quality Assurance (QA) methods with the potential for automation. Her presentation was based on highlights from the Medical Physics contribution discussed at the 3rd ESTRO Forum held recently in Barcelona.

Coetzee believes that QA continues to be at the core of Medical Physicists’ work. It is an essential component for safe, high quality treatments. Results from clinical trials show that poor quality correlates with poor treatment outcomes. However due to the introduction of increasingly complex techniques and technologies, the time needed for QA and dosimetry has increased. Clinical medical physicists spend a great deal of time on routine QA duties, which impacts the available time for other tasks such as clinical dosimetry, development and the implementation of new techniques, management, and teaching and training. Time could be optimised if more of the QA methods were automated.

Unfortunately, automation and its application to QA in RT is still very limited. It is also perceived that some of the quality controls (QCs), metrics and tolerance limits proposed are out-dated by RT technology advances or insufficiently effective to detect at least some errors that may have a clinical impact.

When new technology is being implemented, it is crucial to understand how systems and in particular treatment units behave in order to identify failure modes and design quality controls capable of detecting any delivery error. The principal aim is to ensure the patient receives the dose distribution as planned, and if significant differences are found, these should be reported and if possible re-addressed before the end of the treatment.

“We have now reached a crossroad,” says Coetzee.  “We have to consider whether the original QA paradigms remain appropriate for the new technologies, techniques, and priorities, as well as resource availability.”

Some of the solutions presented include;

  • Widening the scope of the assessment of the results of the QC tests and the decisions taken on its basis, moving from a binary evaluation (pass or fail) to an evaluation of trends (temporary or systematic), using groups of data and applying approaches such as Statistical Process Control.
  • Routine implementation of beam intensity modulation with dynamic treatment techniques such as intensity-modulated RT (IMRT) and volumetric modulated arc therapy (VMAT), which has had a considerable influence on QA procedures.
  • The log file monitoring approach is very attractive as it can be easily automated and does not need any additional equipment. Defenders of log file monitoring argue that it can replace pre-treatment and in vivo dose measurements.
  • Coupled with a suitable machine QA programme, log file analysis undoubtedly has a high potential for treatment delivery checking at the machine level.

Additionally, Coetzee discussed the technical realisation and subsequent clinical implementation of hybrid beam delivery and imaging systems that stimulated research and developments to account for intra- and inter-fraction organ motion, including adaptive RT (ART) approaches. These topics have become central in contemporary Medical Physics research and have eclipsed the more traditional fields of dosimetry, quality assurance and treatment planning.

She also discussed the Medical Physics challenges in proton and particle therapy.  These activities mainly took place in dedicated treatment and/or research centres, however the situation has changed and will continue to do so in the near future. The reasons are multi-layered and include:

  • A pronounced increase in the interest and investment of proton therapy from the radiation oncology community;
  • Adapted solutions from particle therapy vendors offering single room facilities;
  • Proton therapy is rapidly becoming a standard treatment option in several large cancer treatment centres;
  • An increased availability of advanced photon beam therapy and brachytherapy;
  • Consequently, the ‘parallel’ research in photon and particle therapy is likely to discontinue.

Coetzee’s presentation concluded that Medical Physics research and development is a vital area and remains a cornerstone in the further advancement of RT, allowing for safe use of new and individualised techniques and modalities, as well as for a deeper understanding of the clinical outcomes of the treatments of the past. With its highly prolific interdisciplinary meetings and journal, ESTRO continues to provide medical physicists with attractive arenas for scientific exchange and growth.