Aaron Ferguson1, Jonathan McConathy2, Yi Su2, Debra Hewing3, Richard Laforest4. 1. Department of Medical Imaging and Radiation Therapeutics, Saint Louis University, St. Louis, Missouri; and laforestr@mir.wustl.edu aaroneferguson@yahoo.com. 2. Department of Radiology, Washington University School of Medicine, St. Louis, Missouri. 3. Department of Medical Imaging and Radiation Therapeutics, Saint Louis University, St. Louis, Missouri; and. 4. Department of Radiology, Washington University School of Medicine, St. Louis, Missouri laforestr@mir.wustl.edu aaroneferguson@yahoo.com.
Abstract
UNLABELLED: PET/MR offers potential advantages over PET/CT that are currently under investigation. One of the challenges of PET/MR is attenuation correction, as there is no simple correlation between MR signal intensity and the attenuation of 511-keV photons detected in PET. Currently, dedicated MR sequences are used to segment voxels into categories that are then assigned a predetermined attenuation coefficient. MR hardware such as the imaging table, coils, and headphones are also sources of attenuation. The purpose of this study was to evaluate the effect of MR-compatible headphones on average activity concentration measured with PET/MR. We also present a practical approach to correct for the attenuation effect of headphones using a CT-derived attenuation map. METHODS: Phantom studies were performed using a 3-L cylindric phantom containing 55 MBq of (18)F-FDG and water. Images were acquired on a PET/MR device in 2 settings-one with the PET/MR headphones on and one with the headphones off. Phantom images were analyzed to compare activity concentration with headphones on and off. A high-resolution CT and (57)Co transmission scan was obtained to construct a PET attenuation map of the headphones. The resulting attenuation map was registered to the phantom data to evaluate the ability to correct for headphone attenuation. One human subject was scanned to evaluate the clinical impact of headphone attenuation and the accuracy of the proposed correction. RESULTS: Activity concentrations measured in the phantom were reduced by as much as 13.2% with headphones on compared with headphones off. Using the modified attenuation maps that account for attenuation from the headphones resulted in a decrease in the headphone attenuation effect from a maximum of 13.2% to 1.9%. Comparable attenuation effects were observed in the human brain and were similarly reduced with correction using the modified attenuation maps. CONCLUSION: MR-safe headphones were a source of attenuation on our PET/MR phantom and human studies. Attenuation effects of headphones should be considered and can be corrected during quantitative brain PET/MR studies.
UNLABELLED: PET/MR offers potential advantages over PET/CT that are currently under investigation. One of the challenges of PET/MR is attenuation correction, as there is no simple correlation between MR signal intensity and the attenuation of 511-keV photons detected in PET. Currently, dedicated MR sequences are used to segment voxels into categories that are then assigned a predetermined attenuation coefficient. MR hardware such as the imaging table, coils, and headphones are also sources of attenuation. The purpose of this study was to evaluate the effect of MR-compatible headphones on average activity concentration measured with PET/MR. We also present a practical approach to correct for the attenuation effect of headphones using a CT-derived attenuation map. METHODS: Phantom studies were performed using a 3-L cylindric phantom containing 55 MBq of (18)F-FDG and water. Images were acquired on a PET/MR device in 2 settings-one with the PET/MR headphones on and one with the headphones off. Phantom images were analyzed to compare activity concentration with headphones on and off. A high-resolution CT and (57)Co transmission scan was obtained to construct a PET attenuation map of the headphones. The resulting attenuation map was registered to the phantom data to evaluate the ability to correct for headphone attenuation. One human subject was scanned to evaluate the clinical impact of headphone attenuation and the accuracy of the proposed correction. RESULTS: Activity concentrations measured in the phantom were reduced by as much as 13.2% with headphones on compared with headphones off. Using the modified attenuation maps that account for attenuation from the headphones resulted in a decrease in the headphone attenuation effect from a maximum of 13.2% to 1.9%. Comparable attenuation effects were observed in the human brain and were similarly reduced with correction using the modified attenuation maps. CONCLUSION: MR-safe headphones were a source of attenuation on our PET/MR phantom and human studies. Attenuation effects of headphones should be considered and can be corrected during quantitative brain PET/MR studies.
Authors: Mootaz Eldib; Jason Bini; Philip M Robson; Claudia Calcagno; David D Faul; Charalampos Tsoumpas; Zahi A Fayad Journal: Phys Med Biol Date: 2015-05-28 Impact factor: 3.609
Authors: J E Mackewn; J Stirling; S Jeljeli; S-M Gould; R I Johnstone; I Merida; L C Pike; C J McGinnity; K Beck; O Howes; A Hammers; P K Marsden Journal: EJNMMI Phys Date: 2020-05-05