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Cited by 11Medical Imaging Techniques and ApplicationsAdvanced MRI Techniques and ApplicationsAdvanced X-ray and CT Imaging

Standard MRI-based attenuation correction for PET/MRI phantoms: a novel concept using MRI-visible polymer

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Rausch, Ivo, Valladares, Alejandra, Sundar, Lalith Kumar Shiyam, Beyer, Thomas, Hacker, Marcus, Meyerspeer, Martin, Unger, Ewald·2021·EJNMMI Physics
DOI 10.1186/s40658-021-00364-9PMC PMC7892652
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Abstract

Background: PET/MRI phantom studies are challenged by the need of phantom-specific attenuation templates to account for attenuation properties of the phantom material. We present a PET/MRI phantom built from MRI-visible material for which attenuation correction (AC) can be performed using the standard MRI-based AC. Methods: A water-fillable phantom was 3D-printed with a commercially available MRI-visible polymer. The phantom had a cylindrical shape and the fillable compartment consisted of a homogeneous region and a region containing solid rods of different diameters. The phantom was filled with a solution of water and [18F]FDG. A 30 min PET/MRI acquisition including the standard Dixon-based MR-AC method was performed. In addition, a CT scan of the phantom was acquired on a PET/CT system. From the Dixon in-phase, opposed-phase and fat images, a phantom-specific AC map (Phantom MR-AC) was produced by separating the phantom material from the water compartment using a thresholding-based method and assigning fixed attenuation coefficients to the individual compartments. The PET data was reconstructed using the Phantom MR-AC, the original Dixon MR-AC, and an MR-AC just containing the water compartment (NoWall-AC) to estimate the error of ignoring the phantom walls. CT-based AC was employed as the reference standard. Average %-differences in measured activity between the CT corrected PET and the PET corrected with the other AC methods were calculated. Results: The phantom housing and the liquid compartment were both visible and distinguishable from each other in the Dixon images and allowed the segmentation of a phantom-specific MR-based AC. Compared to the CT-AC PET, average differences in measured activity in the whole water compartment in the phantom of −0.3%, 9.4%, and −24.1% were found for Dixon phantom MR-AC, MR-AC, and NoWall-AC based PET, respectively. Average differences near the phantom wall in the homogeneous region were −0.3%, 6.6%, and −34.3%, respectively. Around the rods, activity differed from the CT-AC PET by 0.7%, 8.9%, and −45.5%, respectively. Conclusion: The presented phantom material is visible using standard MR sequences, and thus, supports the use of standard, phantom-independent MR measurements for MR-AC in PET/MRI phantom studies.

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  • Cross-calibration of PET/MRI scanners is generally hampered by water-filled phantoms, which can produce substantial artifacts in the MR-AC sequence with corresponding SUV errors.

    “It should also be noted that cross-calibration of PET/MRI scanners is generally hampered by water-filled phantoms, which are commonly used for SUV calibration in PET/CT and can produce substantial artifacts in the MR-AC sequence with corresponding SUV errors [63,64].”

    From Influences on PET Quantification and Interpretation (2022) · cites this paper as [64]

    The Background (page unavailable) says standard MR attenuation correction can miss phantom materials and thereby underestimate measured activity; the Discussion identifies signal variations and tissue-swap-like artifacts in Dixon images. But the Discussion also says the observed tissue-swap-like artifacts did not enter the phantom-specific MR-AC map. The paper does not establish that artifacts from water-filled phantoms cause substantial SUV errors during cross-calibration. (LLM, conf=0.82)

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Cited by

Sorted by citations

Authors
Rausch, I., Valladares, A., Sundar, L. K. S., Beyer, T., Hacker, M., Meyerspeer, M., & Unger, E.
Affiliations
Medical University of Vienna (AT)
Corresponding author
Rausch, Ivo
ORCID
Venue
EJNMMI Physics
Publisher
Springer Science and Business Media LLC
Published
2021-02-18
Volume
8
Issue
1
Pages
18-18
ISSN
2197-7364 (ISSN-L)
DOI
10.1186/s40658-021-00364-9
PMC
PMC7892652
OpenAlex
W3130762018
Cited by
11
References
2
Citations by year
2025: 3 · 2023: 2 · 2022: 3 · 2021: 3
FWCI
1.06
Type
journal article
Language
en
Open access
Licence
Locations
  • EJNMMI Physics (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • H2020 Marie Skłodowska-Curie Actions (No. 764458)
  • Austrian Science Fund (I3451-N32)
  • Österreichische Forschungsförderungsgesellschaft (858060)
Topics
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Medical Imaging Techniques and Applications
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Advanced MRI Techniques and Applications
  • Physical Sciences › Engineering › Biomedical Engineering › Advanced X-ray and CT Imaging
Keywords
PET/MRI, attenuation correction, Dixon MRI, 3D-printed phantom, 18F-FDG, CT attenuation correction

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