Clinical issues regarding misclassification by Dixon based PET/MR attenuation correction

Title
Clinical issues regarding misclassification by Dixon based PET/MR attenuation correction
Author(s)
공은정조인호
Keywords
POSITRON-EMISSION-TOMOGRAPHY; WHOLE-BODY PET/MRI; TUMOR RESPONSE; F-18-FDG PET; EXPERIENCE; CARCINOMA; ONCOLOGY; THERAPY; SCANNER
Issue Date
201504
Publisher
HELLENIC SOC NUCLEAR MEDICINE
Citation
HELLENIC JOURNAL OF NUCLEAR MEDICINE, v.18, no.1, pp.42 - 47
Abstract
Objective: The Dixon sequence is acquired for attenuation correction (AC) of positron emission tomography (PET) data in integrated PET/magnetic resonance (MR). However it sometimes misclassifies soft tissue and fat in mu-map. In the present study, we investigated factors related to this misclassification and their clinical impacts. Subject and methods: Forty-eight oncological patients (19 males and 29 females, mean age: 59 +/- 11 years old) underwent a single fluorine-18 fluorodeoxyglucose (F-18-FDG) injection/dual-imaging protocol on PET/computed tomography (CT) and subsequently PET/MR. Patients were assigned to either of two groups; group A with a misclassification in at least one bed position or group B with a correctly classified mu-map. We compared body mass index (BMI), lean body mass, fasting duration, volume of hydration and age between group A and group B. In addition, we analyzed the impact of PET quantification using standard uptake ratio (SUR) defined as uptake in volume of interest/uptake in thigh muscle. The Dixon-AC SUR was compared with CT-AC SUR in misclassified bed positions and correctly classified bed positions. All patients were scanned in four bed positions by PET/MR. Ten patients were assigned to group A; six showed misclassification in a bed position (5 in head and 1 in abdomen), three patients in 3 bed positions (head-thorax-abdomen), and one patient in partial bed position in neck. Results: Misclassification was observed in 21% of 48 patients. Group A and group 8 showed no statistically significant differences in BMI, lean body mass, fasting duration or age, however the volume of hydration in group A (245mL) was smaller than in group B (452.6mL) (P=0.027). In group A, we analyzed Dixon-AC SUR/CT-AC SUR ratios in 16 misclassified and 24 correctly classified regions, and ratios in these regions were significant different 0.80 and 0.93, respectively (P=0.046). Conclusion: Because no corrective method has been devised after a scan, we recommend that Dixon images with mu-maps should be checked before interpreting PET/MR images and emphasize the importance of hydration, pre-examination. Misclassification errors do not change the presence of F-18-FDG uptake but can have significant impacts on PET quantification in affected bed positions.
URI
http://hdl.handle.net/YU.REPOSITORY/32825
ISSN
1790-5427
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의과대학 > 핵의학교실 > Articles
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