Impact of gadolinium-based contrast agents on attenuation correction and tracer quantification in neuroendocrine malignancies in [68Ga]-DOTATOC PET/MRI

To investigate the influence of Gadolinium-based contrast agents (CA) on MR-based attenuation correction (MRAC) in evaluating target lesions in [68Ga]Ga-DOTA-TOC. Twenty-four patients with detectable metastases from neuroendocrine tumors underwent whole-body [68Ga]-DOTATOC PET/MRI for staging purposes. According to a consensus reading, 72 target lesions (primaries and metastases) were selected for measurement of standardized uptake values (SUVmax, SUVpeak, SUVmean). High-resolution CAIPI-accelerated Dixon 3D VIBE sequences with bone atlas and truncation correction were acquired before and after contrast agent application. PET data were subsequently reconstructed using both resulting μmaps (MRACnative and MRACpostCA). Each target lesion was assessed in both versions of MRAC-PET utilizing a volume of interest (VOI). Measured values were compared using the Pearson Correlation Coefficient. In addition, a Bland–Altman analysis was performed to determine the limits of agreement (LOA). A strong correlation was achieved for the SUV values before and after contrast medium administration (SUVmax. 0.99; SUVpeak. 0.997; SUVmean. 0.993; p < 0.001). Bland–Altman-analysis, however, showed wider LOA between both PET datasets for SUVmax (4.5 and − 4.7) when compared to SUVpeak (1.7 and − 2.1), and SUVmean (1.8 and − 2.2). No major deviations between the measured values in pre- and post-contrast attenuation-corrected PET images have been observed. Minor alterations may occur due to the application of a contrast medium. This has to be accounted for in patients undergoing repeated PET/MR imaging, especially in the context of therapy monitoring. Our lesion-based analysis examines the impact of gadolinium-based contrast agents on attenuation correction of PET/MRI and the subsequent influence on tracer quantification. Our lesion based approach did not found any major differences between both assessments, indicating that any influence on lesion analysis is negligible.