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Initial clinical evaluation of PET‐based ion beam therapy monitoring under consideration of organ motion
Author(s) -
Kurz Christopher,
Bauer Julia,
Unholtz Daniel,
Richter Daniel,
Herfarth Klaus,
Debus Jürgen,
Parodi Katia
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4940356
Subject(s) - scanner , positron emission tomography , nuclear medicine , iterative reconstruction , medical imaging , dosimetry , medical physics , biomedical engineering , medicine , physics , radiology , optics
Purpose: Intrafractional organ motion imposes considerable challenges to scanned ion beam therapy and demands for a thorough verification of the applied treatment. At the Heidelberg Ion‐Beam Therapy Center (HIT), the scanned ion beam delivery is verified by means of postirradiation positron‐emission‐tomography (PET) imaging. This work presents a first clinical evaluation of PET‐based treatment monitoring in ion beam therapy under consideration of target motion. Methods: Three patients with mobile liver lesions underwent scanned carbon ion irradiation at HIT and postirradiation PET/CT (x‐ray‐computed‐tomography) imaging with a commercial scanner. Respiratory motion was recorded during irradiation and subsequent image acquisition. This enabled a time‐resolved (4D) calculation of the expected irradiation‐induced activity pattern and, for one patient where an additional 4D CT was acquired at the PET/CT scanner after treatment, a motion‐compensated PET image reconstruction. For the other patients, PET data were reconstructed statically. To verify the treatment, calculated prediction and reconstructed measurement were compared with a focus on the ion beam range. Results: Results in the current three patients suggest that for motion amplitudes in the order of 2 mm there is no benefit from incorporating respiratory motion information into PET‐based treatment monitoring. For a target motion in the order of 10 mm, motion‐related effects become more severe and a time‐resolved modeling of the expected activity distribution can lead to an improved data interpretation if a sufficient number of true coincidences is detected. Benefits from motion‐compensated PET image reconstruction could not be shown conclusively at the current stage. Conclusions: The feasibility of clinical PET‐based treatment verification under consideration of organ motion has been shown for the first time. Improvements in noise‐robust 4D PET image reconstruction are deemed necessary to enhance the clinical potential.