ORIGINAL ARTICLE   

The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2023 September;67(3):215-22

DOI: 10.23736/S1824-4785.22.03389-1

Copyright © 2022 EDIZIONI MINERVA MEDICA

lingua: Inglese

11C-methionine PET/MRI in postoperative patients after craniotomy: zero echo time and head atlas versus CT-based attenuation correction

Francesca DE LUCA ^{1, 2} ✉, Martin BOLIN ^{1, 3}, Lennart BLOMQVIST ^{3, 4}, Cecilia WASSBERG ³, Heather MARTIN ², Anna FALK DELGADO ^{1, 2}

¹ Department of Clinical Neuroscience, Karolinska Institute, Solna, Sweden; ² Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden; ³ Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden; ⁴ Department of Molecular Medicine and Surgery Karolinska Institute, Solna, Sweden

BACKGROUND: Attenuation correction (AC) is an important topic in PET/MRI and particularly challenging after brain tumor surgery, near metal implants, adjacent bone and burr holes. In this study, we evaluated the performance of two MR-driven AC methods, zero-echo-time AC (ZTE-AC) and atlas-AC, in comparison to reference standard CT-AC in patients with surgically treated brain tumors at ¹¹C-methionine PET/MRI.
METHODS: This retrospective study investigated seven postoperative patients with neuropathologically confirmed brain tumor at ¹¹C-methionine PET/MRI. Three AC maps - ZTE-AC, atlas-AC and reference standard CT-AC - were generated for each patient. Standardized uptake values (SUV) were obtained at the metal implant, adjacent bone and burr hole. Standard uptake ratio (SUR) SURmetal/mirror, SURbone/mirror and SURburrhole/mirror were then calculated and analyzed with Bland-Altman, Pearson correlation and intraclass correlation reliability.
RESULTS: Smaller mean percent bias range (Bland-Altman) was found for ZTE-AC than atlas-AC in all analyses (metal ZTE -0.46 to -0.02, metal atlas -3.57 to -3.26; bone ZTE -4.60 to -2.16, bone atlas -5.25 to -3.81; burr hole ZTE -0.95 to -0.52, burr hole atlas 7.86 to 8.87). Percent SD range (Bland-Altman) was large for both methods in all analyses, with lower absolute values for ZTE-AC (ZTE 7.02-8.49; atlas 11.47-14.83). A very strong correlation (Pearson correlation) was demonstrated for both methods compared to CT-AC (ZTE ρ 0.97-0.99, P<0.001; atlas ρ 0.88-0.91, P≤0.009) with higher absolute values for ZTE. An excellent intraclass correlation coefficient was found across all analyses for ZTE, atlas and CT maps (ICC ≥0.88).
CONCLUSIONS: ZTE for MR-driven PET attenuation correction presented a more comparable performance to reference standard CT-AC at the postoperative site. ZTE-AC may serve as a useful diagnostic tool for MR-driven AC in patients with surgically treated brain tumors.

KEY WORDS: Positron emission tomography; Magnetic resonance imaging; Brain neoplasms; Methionine methyl ester