Osama Sabri served as the primary investigator for Siemens Healthcare. Osama Sabri and Henryk Barthel received speaker honoraria from Siemens Healthcare. Peter Werner, Michael Rullmann, Anke Bresch, Solveig Tiepolt, Thies Jochimsen, Matthias Schroeter, and Donald Lobsien report no disclosures relevant to the manuscript.
PW contributed to the clinical data collection and nuclear medicine data collection. MR, PW, and TJ contributed to the PET, MRI, and CT data processing and image data analysis. DL contributed to the MRI data analysis and patient treatment. MLS contributed to the patient treatment and contributed to the revised manuscript. HB, PW, and ST contributed to the clinical data analysis and patient treatment. OS and HB contributed to the study concept. All authors participated in the interpretation of the data and in the drafting of the manuscript. All authors read and approved the final version of the manuscript.
In PET/MRI, linear photon attenuation coefficients for attenuation correction (AC) cannot be directly derived, and cortical bone is, so far, usually not considered. This results in an underestimation of the average PET signal in PET/MRI. Recently introduced MR-AC methods predicting bone information from anatomic MRI or proton density-weighted zero-time imaging may solve this problem in the future. However, there is an ongoing debate if the current error is acceptable for clinical use and/or research.
We examined this feature for [18F] fluorodeoxyglucose (FDG) brain PET in 13 patients with clinical signs of dementia or movement disorders who subsequently underwent PET/CT and PET/MRI on the same day. Multiple MR-AC approaches including a CT-derived AC were applied.
The resulting PET data was compared to the CT-derived standard regarding the quantification error and its clinical impact. On a quantitative level, −11.9 to +2 % deviations from the CT-AC standard were found. These deviations, however, did not translate into a systematic diagnostic error. This, as overall patterns of hypometabolism (which are decisive for clinical diagnostics), remained largely unchanged.
Despite a quantitative error by the omission of bone in MR-AC, clinical quality of brain [18F]FDG is not relevantly affected. Thus, brain [18F]FDG PET can already, even now with suboptimal MR-AC, be utilized for clinical routine purposes, even though the MR-AC warrants improvement.