Evaluation of atlas-based attenuation correction for integrated PET/MR in human brain - application of a head atlas and comparison to true CT-based attenuation correction.

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Evaluation of atlas-based attenuation correction for integrated PET/MR in human brain - application of a head atlas and comparison to true CT-based attenuation correction.

J Nucl Med. 2015 Oct 22;

Authors: Sekine T, Buck A, Delso G, Ter Voert E, Huellner M, Veit-Haibach P, Warnock G

Abstract
INTRODUCTION: Attenuation correction (AC) for integrated PET/MRI in human brain is still an open problem. In this study, we evaluated a simplified atlas-based AC (Atlas-AC) by comparing FDG PET data corrected using either Atlas-AC or true CT data (CT-AC).
METHODS: We enrolled 8 patients (median age 63). All patients underwent a clinically indicated whole body (18)F-FDG-PET/CT (GE Healthcare Discovery 690 PET/CT) for staging, re-staging or follow-up of malignant disease. All patients volunteered for an additional PET/MR of the head (GE Healthcare SIGNA PET/MR). For each patient, 2 AC-maps were generated: an Atlas-AC map registered to a patient-specific LAVA-Flex MR sequence and using a vendor-provided head atlas generated from multiple CT head images, and a CT-based AC map. For comparative AC, the CT-AC map generated from PET/CT was superimposed on the Atlas-AC map. Using each AC map, PET images were reconstructed from the list-mode raw data from the PET/MRI scanner. All PET images were normalized to a brain template and FDG accumulation was quantified in 67 volumes-of-interest (VOIs; automated anatomical labeling atlas) using PMOD. Relative difference (%diff) between images based on Atlas-AC and CT-AC was calculated, and averaged difference images were generated. FDG uptake in all VOIs was compared using Bland-Altman analysis.
RESULTS: The range of error in all 536 VOIs was < 10% [range; -3.0% ~ 7.3%]. Whole brain FDG uptake based on Atlas-AC was slightly underestimated (%diff= 2.19±1.40%). The underestimation was most pronounced in the regions below the anterior/posterior commissure line, such as cerebellum, temporal lobe and central structures (%diff=3.69±1.43%, 3.25±1.42%, 3.05±1.18%). This suggests that Atlas-AC tends to underestimate the attenuation values of the skull base bone.
CONCLUSION: The simplified Atlas-AC proved robust and was comparable to the gold-standard CT-AC, although there was a minor underestimation of tracer uptake values close to the base of the skull.

PMID: 26493207 [PubMed - as supplied by publisher]

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