RT Journal Article
SR Electronic
T1 Reproducibility of MR-Based Attenuation Maps in PET/MRI and the Impact on PET Quantification in Lung Cancer
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 999
OP 1004
DO 10.2967/jnumed.117.198853
VO 59
IS 6
A1 Anders Olin
A1 Claes N. Ladefoged
A1 Natasha H. Langer
A1 Sune H. Keller
A1 Johan Löfgren
A1 Adam E. Hansen
A1 Andreas Kjær
A1 Seppo W. Langer
A1 Barbara M. Fischer
A1 Flemming L. Andersen
YR 2018
UL http://jnm.snmjournals.org/content/59/6/999.abstract
AB Quantitative PET/MRI is dependent on reliable and reproducible MR-based attenuation correction (MR-AC). In this study, we evaluated the quality of current vendor-provided thoracic MR-AC maps and further investigated the reproducibility of their impact on 18F-FDG PET quantification in patients with non–small cell lung cancer. Methods: Eleven patients with inoperable non–small cell lung cancer underwent 2–5 thoracic PET/MRI scan–rescan examinations within 22 d. 18F-FDG PET data were acquired along with 2 Dixon MR-AC maps for each examination. Two PET images (PETA and PETB) were reconstructed using identical PET emission data but with MR-AC from these intrasubject repeated attenuation maps. In total, 90 MR-AC maps were evaluated visually for quality and the occurrence of categorized artifacts by 2 PET/MRI-experienced physicians. Each tumor was outlined by a volume of interest (40% isocontour of maximum) on PETA, which was then projected onto the corresponding PETB. SUVmean and SUVmax were assessed from the PET images. Within-examination coefficients of variation and Bland–Altman analyses were conducted for the assessment of SUV variations between PETA and PETB. Results: Image artifacts were observed in 86% of the MR-AC maps, and 30% of the MR-AC maps were subjectively expected to affect the tumor SUV. SUVmean and SUVmax resulted in coefficients of variation of 5.6% and 6.6%, respectively, and scan–rescan SUV variations were within ±20% in 95% of the cases. Substantial SUV variations were seen mainly for scan–rescan examinations affected by respiratory motion. Conclusion: Artifacts occur frequently in standard thoracic MR-AC maps, affecting the reproducibility of PET/MRI. These, in combination with other well-known sources of error associated with PET/MRI examinations, lead to inconsistent SUV measurements in serial studies, which may affect the reliability of therapy response assessment. A thorough visual inspection of the thoracic MR-AC map and Dixon images from which it is derived remains crucial for the detection of MR-AC artifacts that may influence the reliability of SUV.