TY - JOUR T1 - A realistic phantom of the human head for validation of attenuation correction methods in PET-MRI JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 389 LP - 389 VL - 61 IS - supplement 1 AU - Johanna Harries AU - Thies Jochimsen AU - Thomas Scholz AU - Tina Schlender AU - Henryk Barthel AU - Osama Sabri AU - Bernhard Sattler Y1 - 2020/05/01 UR - http://jnm.snmjournals.org/content/61/supplement_1/389.abstract N2 - 389Background: The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) (PET-MRI) is a unique hybrid imaging modality mainly used in oncology and neurology. The MRI-based attenuation correction (MRAC) is crucial for correct quantification of PET data. A suitable phantom to validate quantitative results in PET-MRI is currently missing. In particular, the correction of attenuation due to bone is usually not verified by commonly available phantoms. The aim of this work was to develop such a phantom and to explore whether such a phantom can be used to validate MRACs. Methods: Various materials were investigated for their attenuation and MR properties. For the substitution of bone, water-saturated gypsum plaster was used. The attenuation of 511 keV annihilation photons was regulated by addition of iodine. Fatty tissue was imitated by silicone and brain tissue by agarose gel, respectively. The practicability with respect to the comparison of MRACs was checked as follows: A small flask inserted into the phantom and a large spherical phantom (serving as a reference with negligible error in MRAC) were filled with the very same stock solution. The activity concentration was measured and compared using clinical protocols on PET-MRI and different built-in and offline MRACs. The same measurements were carried out using PET-CT for comparison. Results: The phantom imitates the human head in sufficient detail. All tissue types including bone were detected as such so that the phantom-based comparison of the quantification accuracy of PET-MRI is possible. Quantitatively, the activity concentration in the brain, which was determined using different MRACs, showed a mean deviation of about 5% and a maximum deviation of 11% compared to the spherical phantom. For PET-CT, the deviation was 5%. Conclusions: The comparatively small error in quantification demonstrates that the phantom can be used to validate MRAC methods. Hence, a cross-system comparison towards standardization of the overall quantification performance of various PET-MRI systems, including their MRAC methods, seems to be possible for the first time for brain imaging. Supporting data ER -