Abstract
Object
The aim of this study was to evaluate MR-based attenuation correction of PET emission data of the head, based on a previously described technique that calculates substitute CT (sCT) images from a set of MR images.
Materials and methods
Images from eight patients, examined with 18F-FLT PET/CT and MRI, were included. sCT images were calculated and co-registered to the corresponding CT images, and transferred to the PET/CT scanner for reconstruction. The new reconstructions were then compared with the originals. The effect of replacing bone with soft tissue in the sCT-images was also evaluated.
Results
The average relative difference between the sCT-corrected PET images and the CT-corrected PET images was 1.6 % for the head and 1.9 % for the brain. The average standard deviations of the relative differences within the head were relatively high, at 13.2 %, primarily because of large differences in the nasal septa region. For the brain, the average standard deviation was lower, 4.1 %. The global average difference in the head when replacing bone with soft tissue was 11 %.
Conclusion
The method presented here has a high rate of accuracy, but high-precision quantitative imaging of the nasal septa region is not possible at the moment.
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Acknowledgments
We would like to thank Siemens Healthcare for providing their UTE sequence for this study. This study was jointly supported by the Faculty of Medicine at Umeå University, the University Hospital of Umeå, the Centre for Biomedical Engineering and Physics at Umeå University (CMTF) through EU-project Objective 2 funding, and the Cancer Research Foundation in Northern Sweden.
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Larsson, A., Johansson, A., Axelsson, J. et al. Evaluation of an attenuation correction method for PET/MR imaging of the head based on substitute CT images. Magn Reson Mater Phy 26, 127–136 (2013). https://doi.org/10.1007/s10334-012-0339-2
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DOI: https://doi.org/10.1007/s10334-012-0339-2