Open AccessAttenuation Correction Approaches for Serotonin Transporter Quantification With PET/MRI
Author(s) -
Lucas Rischka,
Gregor Gryglewski,
Neydher Berroterán-Infante,
Ivo Rausch,
G.M. James,
Manfred Klöbl,
Helen Sigurdardottir,
Markus Hartenbach,
Andreas Hahn,
Wolfgang Wadsak,
Markus Mitterhauser,
Thomas Beyer,
Siegfried Kasper,
Daniela Prayer,
Marcus Hacker,
Rupert Lanzenberger
Publication year - 2019
Publication title -
frontiers in physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.32
H-Index - 102
ISSN - 1664-042X
DOI - 10.3389/fphys.2019.01422
Subject(s) - serotonin transporter , correction for attenuation , nuclear medicine , citalopram , segmentation , serotonin , medicine , positron emission tomography , computer science , artificial intelligence , receptor
Background Several MR-based attenuation correction (AC) approaches were developed to conquer the challenging AC in hybrid PET/MR imaging. These AC methods are commonly evaluated on standardized uptake values or tissue concentration. However, in neurotransmitter system studies absolute quantification is more favorable due to its accuracy. Therefore, our aim was to investigate the accuracy of segmentation- and atlas-based MR AC approaches on serotonin transporter (SERT) distribution volumes and occupancy after a drug challenge. Methods 18 healthy subjects (7 male) underwent two [ 11 C]DASB PET/MRI measurements in a double-blinded, placebo controlled, cross-over design. After 70 min the selective serotonin reuptake inhibitor (SSRI) citalopram or a placebo was infused. The parameters total and specific volume of distribution (V T , V S = BP P ) and occupancy were quantified. All subjects underwent a low-dose CT scan as reference AC method. Besides the standard AC approaches DIXON and UTE, a T1-weighted structural image was recorded to estimate a pseudo-CT based on an MR/CT database (pseudoCT). Another evaluated AC approach superimposed a bone model on AC DIXON. Lastly, an approach optimizing the segmentation of UTE images was analyzed (RESOLUTE). PET emission data were reconstructed with all 6 AC methods. The accuracy of the AC approaches was evaluated on a region of interest-basis for the parameters V T , BP P , and occupancy with respect to the results of AC CT. Results Variations for V T and BP P were found with all AC methods with bias ranging from −15 to 17%. The smallest relative errors for all regions were found with AC pseudoCT (<|5%|). Although the bias between BP P SSRI and BP P placebo varied markedly with AC DIXON (<|12%|) and AC UTE (<|9%|), a high correlation to AC CT was obtained ( r 2 ∼1). The relative difference of the occupancy for all tested AC methods was small for SERT high binding regions (<|4%|). Conclusion The high correlation might offer a rescaling from the biased parameters V T and BP P to the true values. Overall, the pseudoCT approach yielded smallest errors and the best agreement with AC CT. For SERT occupancy, all AC methods showed little bias in high binding regions, indicating that errors may cancel out in longitudinal assessments.