title: The Effect of Susceptibility Artifacts Related to Metallic Implants on Adjacent-Lesion Assessment in Simultaneous TOF PET/MR.
abstract: Metalic implants may affect attenuation correction (AC) in PET/MR imaging. The purpose of this study was to evaluate the effect of susceptibility artifacts related to metallic implants on adjacent metabolically active lesions in clinical simultaneous PET/MR scanning for both time-of-flight (TOF) and non-TOF reconstructed PET images.Methods:We included 27 patients without implants but with confirmed18F-FDG-avid lesions adjacent to common implant locations. In all patients, a clinically indicated whole-body18F-FDG PET/MR scan was acquired. Baseline non-TOF and TOF PET images were reconstructed. Reconstruction was repeated after the introduction of artificial signal voids in the AC map to simulate metallic implants in standard anatomic areas. All reconstructed images were qualitatively and quantitatively assessed and compared with the baseline images.Results:In total, 51 lesions were assessed. In 40 and 50 of these cases (non-TOF and TOF, respectively), the detectability of the lesions did not change; in 9 and 1 cases, the detectability changed; and in 2 non-TOF cases, the lesions were no longer visible after the introduction of metallic artifacts. The inclusion of TOF information significantly reduced artifacts due to simulated implants in the femoral head, sternum, and spine (P= 0.01, 0.01, and 0.03, respectively). It also improved image quality in these locations (P= 0.02, 0.01, and 0.01, respectively). The mean percentage error was -3.5% for TOF and -4.8% for non-TOF reconstructions, meaning that the inclusion of TOF information reduced the percentage error in SUVmaxby 28.5% (P< 0.01).Conclusion:Qualitatively, there was a significant reduction of artifacts in the femoral head, sternum, and spine. There was also a significant qualitative improvement in image quality in these locations. Furthermore, our study indicated that simulated susceptibility artifacts related to metallic implants have a significant effect on small, moderately18F-FDG-avid lesions near the implant site that possibly may go unnoticed without TOF information. On larger, highly18F-FDG-avid lesions, the metallic implants had only a limited effect. The largest significant quantitative difference was found in artifacts of the sternum. There was only a weak inverse correlation between lesions affected by artifacts and distance from the implant.
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.|Department of Nuclear Medicine, Sant'Orsola Hospital, University of Bologna, Bologna, Italy.
authors.forename: Hanna
authors.initials: H
authors.lastname: Svirydenka
authors.affiliation: GE Healthcare, Waukesha, Wisconsin.
authors.forename: Gaspar
authors.initials: G
authors.lastname: Delso
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Felipe
authors.initials: F
authors.lastname: De Galiza Barbosa
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.|Department of Neuroradiology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Huellner
authors.affiliation: Department of Medical Physics, Royal United Hospitals Bath NHS Foundation Trust, Bath, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Davison
authors.affiliation: Department of Nuclear Medicine, Sant'Orsola Hospital, University of Bologna, Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Fanti
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.|Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland; and.|University of Zurich, Zurich, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Veit-Haibach
authors.affiliation: Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland edwin.tervoert@usz.ch.|University of Zurich, Zurich, Switzerland.
authors.forename: Edwin E G W
authors.initials: EEGW
authors.lastname: Ter Voert
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008670:Metals; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D009369:Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D019736:Prostheses and Implants; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D008670:Metals
keywords: PET/MR; clinical; metal artifacts; simulation; tumor