Abstract
BackgroundThis study aims to compare proton density weighted magnetic resonance imaging (MRI) zero echo time (ZTE) and head atlas attenuation correction (AC) to the reference standard computed tomography (CT) based AC for 11C-methionine positron emission tomography (PET)/MRI.MethodsA retrospective cohort of 14 patients with suspected or confirmed brain tumour and 11C-Methionine PET/MRI was included in the study. For each scan, three AC maps were generated: ZTE–AC, atlas-AC and reference standard CT-AC. Maximum and mean standardised uptake values (SUV) were measured in the hotspot, mirror region and frontal cortex. In postoperative patients (n = 8), SUV values were additionally obtained adjacent to the metal implant and mirror region. Standardised uptake ratios (SUR) hotspot/mirror, hotspot/cortex and metal/mirror were then calculated and analysed with Bland–Altman, Pearson correlation and intraclass correlation reliability in the overall group and subgroups.ResultsZTE–AC demonstrated narrower SD and 95% CI (Bland–Altman) than atlas-AC in the hotspot analysis for all groups (ZTE overall ≤ 2.84, − 1.41 to 1.70; metal ≤ 1.67, − 3.00 to 2.20; non-metal ≤ 3.04, − 0.96 to 3.38; Atlas overall ≤ 4.56, − 1.05 to 3.83; metal ≤ 3.87, − 3.81 to 4.64; non-metal ≤ 4.90, − 1.68 to 5.86). The mean bias for both ZTE–AC and atlas-AC was ≤ 2.4% compared to CT-AC. In the metal region analysis, ZTE–AC demonstrated a narrower mean bias range—closer to zero—and narrower SD and 95% CI (ZTE 0.21–0.48, ≤ 2.50, − 1.70 to 2.57; Atlas 0.56–1.54, ≤ 4.01, − 1.81 to 4.89). The mean bias for both ZTE–AC and atlas-AC was within 1.6%. A perfect correlation (Pearson correlation) was found for both ZTE–AC and atlas-AC compared to CT-AC in the hotspot and metal analysis (ZTE ρ 1.00, p < 0.0001; atlas ρ 1.00, p < 0.0001). An almost perfect intraclass correlation coefficient for absolute agreement was found between Atlas-, ZTE and CT maps for maxSUR and meanSUR values in all the analyses (ICC > 0.99).ConclusionsBoth ZTE and atlas-AC showed a good performance against CT-AC in patients with brain tumour.
Highlights
This study aims to compare proton density weighted magnetic resonance imaging (MRI) zero echo time (ZTE) and head atlas attenuation correction (AC) to the reference standard computed tomography (CT) based AC for 11C-methionine positron emission tomography (PET)/MRI
A recently developed template-based method, Zero Echo Time (ZTE), for AC in positron emission tomography/ magnetic resonance imaging (PET/MRI) has been developed and tested in non-surgical patients, providing an accurate AC map when compared to attenuation correction with PET emission scan [10, 18, 22, 23]. The aim of this current study is to further evaluate ZTE–AC in preand postoperative patients with suspected or confirmed brain tumour for correct standardised uptake values (SUV) quantification in the presence of surgical metal implants and clinical use of PET/ MRI study of brain tumours
The aim of the study is to retrospectively investigate ZTE–AC and atlas-AC compared to the reference standard CT-AC for MET PET/MRI in pre- and postoperative patients with suspected or confirmed brain tumour
Summary
This study aims to compare proton density weighted magnetic resonance imaging (MRI) zero echo time (ZTE) and head atlas attenuation correction (AC) to the reference standard computed tomography (CT) based AC for 11C-methionine positron emission tomography (PET)/MRI. The distribution of 11C-methionine has potential to characterise primary brain tumour/metastases, assess the efficacy of oncological treatment and differentiate radionecrosis from tumour recurrence [3,4,5]. Due to these characteristics, 11C-methionine provides a higher selectivity for the identification of brain gliomas, especially for hypo- or isometabolic lesions on 18F-Flurodeoxyglucose (FDG) PET [6, 7] and a diagnostic accuracy similar to 18F-fluoroethyl-l-tyrosine (FET) [8]. In comparison to PET/CT, PET/MRI lacks a clinically accepted standard method to directly obtain AC maps
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