Josefine Handrack1, Thomas Tessonnier1,2, Wenjing Chen3, Jakob Liebl3,4, Jürgen Debus1,3, Julia Bauer1,3, Katia Parodi1,2. 1. a Department of Radiation Oncology , Universitätsklinikum Heidelberg , Heidelberg , Germany. 2. b Department of Medical Physics , Ludwig-Maximilians-Universität München , Munich , Germany. 3. c Heidelberg Ion-Beam Therapy Centre , Heidelberg , Germany. 4. d EBG MedAustron GmbH , Wiener-Neustadt , Austria.
Abstract
BACKGROUND: Ion therapy, especially with modern scanning beam delivery, offers very sharp dose gradients for highly conformal cancer treatment. However, it is very sensitive to uncertainties of tissue stopping properties as well as to anatomical changes and setup errors, making range verification highly desirable. To this end, positron emission tomography (PET) can be used to measure decay products of β+-emitters created in interactions inside the patient. This work investigates the sensitivity of post treatment PET/CT (computed tomography) to detect inter-fractional range variations. MATERIAL AND METHODS: Fourteen patients of different indication underwent PET/CT monitoring after selected treatment fractions with scanned proton or carbon ion beams. In addition to PET/CT measurements, PET and dose distributions were simulated on different co-registered CT data. Pairs of PET data were then analyzed in terms of longitudinal shifts along the beam path, as surrogate of inter-fractional range deviations. These findings were compared to changes of dose-volume-histogram indexes and corresponding dose as well as CT shifts to disentangle the origin of possible PET shifts. RESULTS: Biological washout modeling (PET simulations) and low (<55 Bq/ml) activity concentrations (offline PET measurements, especially for 12C ions) were the main limitations for clinical treatment verification. For two selected cases, the benefit of improved washout modeling based on organ segmentation could be demonstrated. Overall, inter-fractional range shifts up to ±3 mm could be deduced from both PET measurements and simulations, and found well correlated (typically within 1.8 mm) to anatomical changes derived from CT scans, in agreement with dose data. CONCLUSIONS: Despite known limitations of post treatment PET/CT imaging, this work indicates its potential for assessing inter-fractional changes and points to future developments for improved PET-based treatment verification.
BACKGROUND: Ion therapy, especially with modern scanning beam delivery, offers very sharp dose gradients for highly conformal cancer treatment. However, it is very sensitive to uncertainties of tissue stopping properties as well as to anatomical changes and setup errors, making range verification highly desirable. To this end, positron emission tomography (PET) can be used to measure decay products of β+-emitters created in interactions inside the patient. This work investigates the sensitivity of post treatment PET/CT (computed tomography) to detect inter-fractional range variations. MATERIAL AND METHODS: Fourteen patients of different indication underwent PET/CT monitoring after selected treatment fractions with scanned proton or carbon ion beams. In addition to PET/CT measurements, PET and dose distributions were simulated on different co-registered CT data. Pairs of PET data were then analyzed in terms of longitudinal shifts along the beam path, as surrogate of inter-fractional range deviations. These findings were compared to changes of dose-volume-histogram indexes and corresponding dose as well as CT shifts to disentangle the origin of possible PET shifts. RESULTS: Biological washout modeling (PET simulations) and low (<55 Bq/ml) activity concentrations (offline PET measurements, especially for 12C ions) were the main limitations for clinical treatment verification. For two selected cases, the benefit of improved washout modeling based on organ segmentation could be demonstrated. Overall, inter-fractional range shifts up to ±3 mm could be deduced from both PET measurements and simulations, and found well correlated (typically within 1.8 mm) to anatomical changes derived from CT scans, in agreement with dose data. CONCLUSIONS: Despite known limitations of post treatment PET/CT imaging, this work indicates its potential for assessing inter-fractional changes and points to future developments for improved PET-based treatment verification.
Authors: Daria Boscolo; Daria Kostyleva; Mohammad Javad Safari; Vasiliki Anagnostatou; Juha Äystö; Soumya Bagchi; Tim Binder; Georgios Dedes; Peter Dendooven; Timo Dickel; Vasyl Drozd; Bernhard Franczack; Hans Geissel; Chiara Gianoli; Christian Graeff; Tuomas Grahn; Florian Greiner; Emma Haettner; Roghieh Haghani; Muhsin N Harakeh; Felix Horst; Christine Hornung; Jan-Paul Hucka; Nasser Kalantar-Nayestanaki; Erika Kazantseva; Birgit Kindler; Ronja Knöbel; Natalia Kuzminchuk-Feuerstein; Bettina Lommel; Ivan Mukha; Chiara Nociforo; Shunki Ishikawa; Giulio Lovatti; Munetaka Nitta; Ikechi Ozoemelam; Stephane Pietri; Wolfgang R Plaß; Andrej Prochazka; Sivaji Purushothaman; Claire-Anne Reidel; Heidi Roesch; Fabio Schirru; Christoph Schuy; Olga Sokol; Timo Steinsberger; Yoshiki K Tanaka; Isao Tanihata; Peter Thirolf; Walter Tinganelli; Bernd Voss; Uli Weber; Helmut Weick; John S Winfield; Martin Winkler; Jianwei Zhao; Christoph Scheidenberger; Katia Parodi; Marco Durante Journal: Front Oncol Date: 2021-08-19 Impact factor: 5.738