Experimental investigation of irregular motion impact on 4D PET-based particle therapy monitoring. (6th January 2016)

• Record Type: Journal Article
• Authors: Tian, Y; Stützer, K; Enghardt, W; Priegnitz, M; Helmbrecht, S; Bert, C; Fiedler, F
• Is Part Of: Physics in medicine & biology. Volume 61:Number 2(2016:Jan.)
• Page Start: N20
• Page End: N34
• Publication Date: 2016-01-06
• Subjects: irregular target motion -- 4D PET -- particle therapy -- dose monitoring; Biophysics -- Periodicals; Medical physics -- Periodicals; 610.153
• DOI: 10.1088/0031-9155/61/2/N20
• Languages: English
• ISSNs: 0031-9155

Abstract

Abstract: Particle therapy positron emission tomography (PT-PET) is an in vivo and non-invasive imaging technique to monitor treatment delivery in particle therapy. The inevitable patient respiratory motion during irradiation causes artefacts and inaccurate activity distribution in PET images. Four-dimensional (4D) maximum likelihood expectation maximisation (4D MLEM) allows for a compensation of these effects, but has up to now been restricted to regular motion for PT-PET investigations. However, intra-fractional motion during treatment might differ from that during acquisition of the 4D-planning CT (e.g. amplitude variation, baseline drift) and therefore might induce inaccurate 4D PET reconstruction results. This study investigates the impact of different irregular analytical one-dimensional (1D) motion patterns on PT-PET imaging by means of experiments with a radioactive source and irradiated moving phantoms. Three sorting methods, namely phase sorting, equal amplitude sorting and event-based amplitude sorting, were applied to manage the PET list-mode data. The influence of these sorting methods on the motion compensating algorithm has been analysed. The event-based amplitude sorting showed a superior performance and it is applicable for irregular motions with ⩽4 mm amplitude elongation and drift. For motion with 10 mm baseline drift, the normalised root mean square error was as high as 10.5% and a 10 mm range deviation was observed.