Reliability of semiquantitative 18F-FDG PET parameters derived from simultaneous brain PET/MRI: A feasibility study

Abstract

PurposeSimultaneous brain PET/MRI faces an important issue of validation of accurate MRI based attenuation correction (AC) method for precise quantitation of brain PET data unlike in PET/CT systems where the use of standard, validated CT based AC is routinely available. The aim of this study was to investigate the feasibility of evaluation of semiquantitative 18F-FDG PET parameters derived from simultaneous brain PET/MRI using ultrashort echo time (UTE) sequences for AC and to assess their agreement with those obtained from PET/CT examination. MethodsSixteen patients (age range 18–73 years; mean age 49.43 (19.3) years; 13 men 3 women) underwent simultaneous brain PET/MRI followed immediately by PET/CT. Quantitative analysis of brain PET images obtained from both studies was undertaken using Scenium v.1 brain analysis software package. Twenty ROIs for various brain regions were system generated and 6 semiquantitative parameters including maximum standardized uptake value (SUV max), SUV mean, minimum SUV (SUV min), minimum standard deviation (SD min), maximum SD (SD max) and SD from mean were calculated for both sets of PET data for each patient. Intra-class correlation coefficients (ICCs) were determined to assess agreement between the various semiquantitative parameters for the two PET data sets. ResultsIntra-class co-relation between the two PET data sets for SUV max, SUV mean and SD max was highly significant (p<0.00) for all the 20 predefined brain regions with ICC>0.9. SD from mean was also found to be statistically significant for all the predefined brain regions with ICC>0.8. However, SUV max and SUV mean values obtained from PET/MRI were significantly lower compared to those of PET/CT for all the predefined brain regions. ConclusionPET quantitation accuracy using the MRI based UTE sequences for AC in simultaneous brain PET/MRI is reliable in a clinical setting, being similar to that obtained using PET/CT.