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Verfasst von:Kurz, Christopher [VerfasserIn]   i
 Bauer, Julia [VerfasserIn]   i
 Parodi, Katia [VerfasserIn]   i
Titel:Investigating the limits of PET/CT imaging at very low true count rates and high random fractions in ion-beam therapy monitoring
Verf.angabe:Christopher Kurz and Julia Bauer, Heidelberg Ion-Beam Therapy Center and Department of Radiation Oncology, Heidelberg University Hospital; Maurizio Conti, Laura Guérin, and Lars Eriksson, Siemens Healthcare Molecular Imaging, Knoxville, Tennessee; Katia Parodi, Heidelberg Ion-Beam Therapy Center and Department of Radiation Oncology, Heidelberg University Hospital
E-Jahr:2015
Jahr:10 June 2015
Umfang:13 S.
Fussnoten:Gesehen am 29.03.2017
Titel Quelle:Enthalten in: Medical physics
Ort Quelle:Hoboken, NJ : Wiley, 1974
Jahr Quelle:2015
Band/Heft Quelle:42(2015), 7, Seite 3979-3991
ISSN Quelle:2473-4209
 1522-8541
Abstract:Purpose: External beam radiotherapy with protons and heavier ions enables a tighter conformation of the applied dose to arbitrarily shaped tumor volumes with respect to photons, but is more sensitive to uncertainties in the radiotherapeutic treatment chain. Consequently, an independent verification of the applied treatment is highly desirable. For this purpose, the irradiation-induced β+-emitter distribution within the patient is detected shortly after irradiation by a commercial full-ring positron emission tomography/x-ray computed tomography (PET/CT) scanner installed next to the treatment rooms at the Heidelberg Ion-Beam Therapy Center (HIT). A major challenge to this approach is posed by the small number of detected coincidences. This contribution aims at characterizing the performance of the used PET/CT device and identifying the best-performing reconstruction algorithm under the particular statistical conditions of PET-based treatment monitoring. Moreover, this study addresses the impact of radiation background from the intrinsically radioactive lutetium-oxyorthosilicate (LSO)-based detectors at low counts. Methods: The authors have acquired 30 subsequent PET scans of a cylindrical phantom emulating a patientlike activity pattern and spanning the entire patient counting regime in terms of true coincidences and random fractions (RFs). Accuracy and precision of activity quantification, image noise, and geometrical fidelity of the scanner have been investigated for various reconstruction algorithms and settings in order to identify a practical, well-suited reconstruction scheme for PET-based treatment verification. Truncated listmode data have been utilized for separating the effects of small true count numbers and high RFs on the reconstructed images. A corresponding simulation study enabled extending the results to an even wider range of counting statistics and to additionally investigate the impact of scatter coincidences. Eventually, the recommended reconstruction scheme has been applied to exemplary postirradiation patient data-sets. Results: Among the investigated reconstruction options, the overall best results in terms of image noise, activity quantification, and accurate geometrical recovery were achieved using the ordered subset expectation maximization reconstruction algorithm with time-of-flight (TOF) and point-spread function (PSF) information. For this algorithm, reasonably accurate (better than 5%) and precise (uncertainty of the mean activity below 10%) imaging can be provided down to 80 000 true coincidences at 96% RF. Image noise and geometrical fidelity are generally improved for fewer iterations. The main limitation for PET-based treatment monitoring has been identified in the small number of true coincidences, rather than the high intrinsic random background. Application of the optimized reconstruction scheme to patient data-sets results in a 25% − 50% reduced image noise at a comparable activity quantification accuracy and an improved geometrical performance with respect to the formerly used reconstruction scheme at HIT, adopted from nuclear medicine applications. Conclusions: Under the poor statistical conditions in PET-based treatment monitoring, improved results can be achieved by considering PSF and TOF information during image reconstruction and by applying less iterations than in conventional nuclear medicine imaging. Geometrical fidelity and image noise are mainly limited by the low number of true coincidences, not the high LSO-related random background. The retrieved results might also impact other emerging PET applications at low counting statistics.
DOI:doi:10.1118/1.4921995
URL:Bitte beachten Sie: Dies ist ein Bibliographieeintrag. Ein Volltextzugriff für Mitglieder der Universität besteht hier nur, falls für die entsprechende Zeitschrift/den entsprechenden Sammelband ein Abonnement besteht oder es sich um einen OpenAccess-Titel handelt.

Volltext ; Verlag: http://dx.doi.org/10.1118/1.4921995
 Volltext: http://onlinelibrary.wiley.com/doi/10.1118/1.4921995/abstract
 DOI: https://doi.org/10.1118/1.4921995
Datenträger:Online-Ressource
Sprache:eng
Sach-SW:Biological material, e.g. blood, urine
 Computed tomography
 Computerised tomographs
 Data analysis
 Digital computing or data processing equipment or methods, specially adapted for specific applications
 expectation-maximisation algorithm
 Haemocytometers
 Halo
 Image data processing or generation, in general
 image denoising
 Image enhancement or restoration, e.g. from bit-mapped to bit-mapped creating a similar image
 image reconstruction
 Image scanners
 Ion beams
 ion beam therapy
 low statistics PET imaging
 Measuring half-life of a radioactive substance
 Medical image noise
 medical image processing
 Medical image reconstruction
K10plus-PPN:1556059256
Verknüpfungen:→ Zeitschrift

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