Julia Thiele:
Immobilisation for proton beam therapy of tumours in the abdomen
Julia Thiele1, Sergej Schneider2,3, Chiara
Valentini1,2, Fabian Lohaus1,2, Danilo Haak1,
Mechthild Krause1-5, Christian Richter1-3, Esther G.C. Troost1-5.
1 Department of
Radiotherapy and Radiation Oncology, Faculty of Medicine and University
Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
2 OncoRay - National
Center for Radiation Research in Oncology, Faculty of Medicine and University
Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum
Dresden – Rossendorf, Dresden, Germany
3 Institute of
Radiooncology - OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Rossendorf,
Germany
4 German
Cancer Consortium (DKTK), Partner Site Dresden, and German Cancer Research
Center (DKFZ), Heidelberg, Germany
5 National Center for
Tumor Diseases (NCT), Partner Site Dresden, Germany: German Cancer Research
Center (DKFZ), Heidelberg, Germany; Faculty of Medicine and University Hospital
Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany, and;
Helmholtz Association / Helmholtz-Zentrum Dresden - Rossendorf (HZDR), Dresden,
Germany;
Abstract:
Due to the physical characteristics
of protons, proton beam therapy (PTx) differs from photon treatment, in terms
of radiation field arrangement, dose distribution, and uncertainty in dose
deposition. Therefore, although the immobilization procedure is similar, some
peculiarities must be taken into account, since even the image guided radiotherapy
(IGRT) methods are also differently applied, with e.g., bony setup being
mandatory for PTx.
In the University Proton Therapy
Dresden, selected patients with tumours of the upper abdomen are treated with
proton therapy. Before simulation, three
(gold) fiducial markers are implanted in the proximity of the tumour. Abdominal
corsets [Schneider] or compression devices to reduce respiratory motion in the
target volume are used for computer tomography (CT)-based treatment planning
and daily PTx application. Moreover, the planning-CT is performed as a 4D-CT; target
volumes, organs at risk and the fiducial markers are contoured on each of the eight
breathing phases and on the average CT. The PTx planning needs to be robust in
order to take movement of target structures and organs at risk into account. In
general, a pencil beam scanning technique (PBS) is applied.
Daily setup of the patient is performed
relying on bony anatomy. In orthogonal X-ray imaging or in-room CT, the
position of the fiducials can be visualised. The aim is to assure that the
fiducials are inside a margin of 3 – 5 mm compared to planning CT.
During the 6-week treatment,
anatomical changes may influence the dose distribution of PTx. Therefore, to evaluate possible changes in
dose distributions and possibly re-optimize the treatment plan based on these
changes, a 4D control-CT is performed weekly starting from the second week of
treatment.
Referenz:
Schneider, S. „Inter- and
Intrafraction motion management for MR guided Proton Therapy of Pancreatic
Carcinoma “, 2020