Medical physics research projects

Flattening-filter-free photon beams and mARC rotation techniques

Modern radiotherapy techniques allow the creation of highly complex three-dimensional dose distributions, which closely conform to the target volume while sparing neighbouring organs at risk.

In the past years, different technical advances have been introduced with the aim of reducing treatment times. In addition to providing a relief to the patient undergoing treatment and a relaxation of the clinical schedule, faster treatment offers the advantage of reducing spurious patient motion during irradiation, making treatment more precise and reducing the need for expanded set-up margins. Optimal treatment will therefore be a combination of highly conformal and fast irradiation techniques with image-guided radiotherapy (IGRT).

The two main approaches to reducing treatment times are the use of high dose-rate flattening-filter-free photon beams and volumetric modulated arc therapies or other kinds of rotational IMRT treatment.

At the Siemens Artiste linear accelerators of the Department of Radiotherapy and Radiation Oncology, the rotational IMRT technique mARC and the flattening-filter-free photon energy 7 MV are available.

One focus of the medical-physics research over the past years has been on the dosimetrical and physical characterisation of these new techniques and their implementation in the treatment planning System. On this basis, the clinical use of the treatment techniques was evaluated by a number of planning studies for the treatment of brain metastases, head-and-neck and prostate cancer patients. Afterwards, both techniques were taken into first clinical use. Furthermore, two conversion algorithms were programmed to allow the creation of mARC plans by non-dedicated planning systems; either on the basis of step-and-shoot IMRT plans or by conversion of SmartArc plans in Philips Pinnacle.

Publications about the flattening-filter-free beam energy

1. Dzierma Y, Licht N, Nuesken F, Ruebe C. Beam properties and stability of a flattening-filter free 7 MV beam-an overview. Med Phys. 2012 May; 39(5):2595-602. doi: 10.1118/1.3703835. PubMed PMID: 22559630
2. Dzierma Y, Nuesken FG, Palm J, Licht NP, Ruebe C. Planning study and dose measurements of intracranial stereotactic radiation surgery with a flattening filter-free linac. Pract Radiat Oncol. 2014 Mar-Apr;4(2):e109-16. doi:10.1016/j.prro.2013.04.004. Epub 2013 Jun 3. PubMed PMID: 24890356.
3. Dzierma Y, Nuesken FG, Fleckenstein J, Melchior P, Licht NP, Rübe C. Comparative planning of flattening-filter-free and flat beam IMRT for hypopharynx cancer as a function of beam and segment number. PLoS One. 2014 Apr 10;9(4):e94371. doi: 10.1371/journal.pone.0094371. eCollection 2014. PubMed PMID: 24722621; PubMed Central PMCID: PMC3983129.

• Siemens white paper about FFF

Publications about the mARC rotational technique

1. Dzierma Y, Nuesken F, Licht N, Ruebe C. A novel implementation of mARC treatment for non-dedicated planning systems using converted IMRT plans. Radiat Oncol. 2013 Aug 3;8(1):193. [Epub ahead of print] PubMed PMID: 23915350; PubMed Central PMCID: PMC3750816.
2. Dzierma Y, Nuesken FG, Kremp S, Palm J, Licht NP, Rübe C. Commissioning and first clinical application of mARC treatment. Strahlenther Onkol. 2014 Apr 29. PubMed PMID: 24777584.
3. Dzierma Y, Bell K, Palm J, Nuesken F, Licht N, Rübe Ch. mARC vs. IMRT radiotherapy of the prostate with flat and flattening-filter-free beam energies, Radiat Oncol 2014;9:250.
4. Dzierma Y, Licht N, Norton I, Nuesken F, Rübe Ch, Fleckenstein J. VMAT to arclet plan conversion in a treatment planning system, Strahlenther Onkol, in press (published online 7 Sep 2015).

• Siemens white paper about mARC