title: Impact of MR-safe headphones on PET attenuation in combined PET/MRI scans.
abstract: BACKGROUND
  MR headphones are attenuation sources affecting PET quantification in hybrid PET/MRI. Despite potentially better patient communication, usage in PET/MRI scans is not approved by the vendor. This study aims to determine the impact of headphones on PET by means of phantom and patient scans. Additionally, the perceived benefit of using headphones was evaluated.
  
  
  RESULTS
  A cylinder phantom was scanned without and with dedicated MR headphones in a PET/CT scanner. Headphone attenuation was additionally assessed in a clinical setup in 10 patients on a PET/MR scanner using F-18-fluoro-deoxy-glucose. The difference in tracer uptake with and without headset was determined for the various brain regions. Additionally, the patients were asked for differences in noise levels, patient comfort, communication quality, and preference. CT data revealed headphone attenuation values of 350-500 HU. Neglecting headphone attenuation leads to a decrease in PET values between the earcups of about 11 % when compared to the correctly reconstructed data. Regions further away from the headphones were less affected. Patient images demonstrated a decrease of 11 % on average in the cerebellum and temporal lobes, while other regions were less affected. No visual artefacts in the images were noticed. On average, no advantage in terms of noise and patient comfort and only slightly better quality of communication were imparted by the patients.
  
  
  CONCLUSIONS
  Using headphones during PET/MR acquisition leads to a negative bias in brain uptake values without introducing obvious image artefacts. Since they lack benefits for the patients, they should be avoided if PET quantification of the brain is needed.
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, 48149, Münster, Germany. butherf@uni-muenster.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Büther
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, 48149, Münster, Germany. vrachal@uni-muenster.de.
authors.forename: Alexis
authors.initials: A
authors.lastname: Vrachimis
authors.affiliation: Department of Clinical Radiology, University Hospital Münster, Albert-Schweitzer-Campus 1, 48149, Münster, Germany. anne.becker@ukmuenster.de.
authors.forename: Anne
authors.initials: A
authors.lastname: Becker
authors.affiliation: Department of Nuclear Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, 48149, Münster, Germany. stegger@uni-muenster.de.
authors.forename: Lars
authors.initials: L
authors.lastname: Stegger
keywords: Artefacts; Attenuation correction; MR headphones; PET/MRI