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Updated: May 8, 2026
Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
Published on: December 18, 2016
MR-based attenuation correction methods for improved PET quantification in lesions within bone and susceptibility
Ilja Bezrukov1, Holger Schmidt, Frédéric Mantlik
1Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany.
Unlabelled:
Hybrid PET/MR systems have recently entered clinical practice. Thus, the accuracy of MR-based attenuation correction in simultaneously acquired data can now be investigated. We assessed the accuracy of 4 methods of MR-based attenuation correction in lesions within soft tissue, bone, and MR susceptibility artifacts: 2 segmentation-based methods (SEG1, provided by the manufacturer, and SEG2, a method with atlas-based susceptibility artifact correction); an atlas- and pattern recognition-based method (AT&PR), which also used artifact correction; and a new method combining AT&PR and SEG2 (SEG2wBONE).
Methods:
Attenuation maps were calculated for the PET/MR datasets of 10 patients acquired on a whole-body PET/MR system, allowing for simultaneous acquisition of PET and MR data. Eighty percent iso-contour volumes of interest were placed on lesions in soft tissue (n = 21), in bone (n = 20), near bone (n = 19), and within or near MR susceptibility artifacts (n = 9). Relative mean volume-of-interest differences were calculated with CT-based attenuation correction as a reference.
Results:
For soft-tissue lesions, none of the methods revealed a significant difference in PET standardized uptake value relative to CT-based attenuation correction (SEG1, -2.6% ± 5.8%; SEG2, -1.6% ± 4.9%; AT&PR, -4.7% ± 6.5%; SEG2wBONE, 0.2% ± 5.3%). For bone lesions, underestimation of PET standardized uptake values was found for all methods, with minimized error for the atlas-based approaches (SEG1, -16.1% ± 9.7%; SEG2, -11.0% ± 6.7%; AT&PR, -6.6% ± 5.0%; SEG2wBONE, -4.7% ± 4.4%). For lesions near bone, underestimations of lower magnitude were observed (SEG1, -12.0% ± 7.4%; SEG2, -9.2% ± 6.5%; AT&PR, -4.6% ± 7.8%; SEG2wBONE, -4.2% ± 6.2%). For lesions affected by MR susceptibility artifacts, quantification errors could be reduced using the atlas-based artifact correction (SEG1, -54.0% ± 38.4%; SEG2, -15.0% ± 12.2%; AT&PR, -4.1% ± 11.2%; SEG2wBONE, 0.6% ± 11.1%).
Conclusion:
For soft-tissue lesions, none of the evaluated methods showed statistically significant errors. For bone lesions, significant underestimations of -16% and -11% occurred for methods in which bone tissue was ignored (SEG1 and SEG2). In the present attenuation correction schemes, uncorrected MR susceptibility artifacts typically result in reduced attenuation values, potentially leading to highly reduced PET standardized uptake values, rendering lesions indistinguishable from background. While AT&PR and SEG2wBONE show accurate results in both soft tissue and bone, SEG2wBONE uses a two-step approach for tissue classification, which increases the robustness of prediction and can be applied retrospectively if more precision in bone areas is needed.
Insights
Four methods for MR-based attenuation correction in hybrid PET/MR imaging were evaluated. The SEG2wBONE method demonstrated accurate PET quantification in soft tissue and bone lesions, especially when dealing with MR susceptibility artifacts.
Area of Science:
- Medical Imaging
- Nuclear Medicine
- Radiology
Background:
- Hybrid PET/MR systems are increasingly used in clinical practice.
- Accurate attenuation correction is crucial for quantitative PET imaging.
- MR-based attenuation correction methods require validation for simultaneously acquired data.
Purpose of the Study:
- To assess the accuracy of four MR-based attenuation correction methods in hybrid PET/MR imaging.
- To evaluate performance in soft tissue, bone, and MR susceptibility artifact regions.
- To compare methods against CT-based attenuation correction.
Main Methods:
- Four attenuation correction methods were evaluated: SEG1, SEG2, AT&PR, and SEG2wBONE.
- PET/MR datasets from 10 patients were analyzed.
- Volumes of interest were placed on lesions in various locations, and relative differences to CT-based correction were calculated.
Main Results:
- No significant differences were found for soft-tissue lesions across all methods.
- All methods underestimated PET values in bone lesions, with SEG2wBONE showing the smallest error (-4.7% ± 4.4%).
- SEG2wBONE and AT&PR demonstrated accurate results for lesions affected by MR susceptibility artifacts, with errors of 0.6% ± 11.1% and -4.1% ± 11.2%, respectively.
Conclusions:
- SEG1 and SEG2 methods showed significant underestimation for bone lesions.
- MR susceptibility artifacts can lead to substantial quantification errors if uncorrected.
- SEG2wBONE offers accurate PET quantification in diverse lesion types and locations, with improved robustness for bone imaging.
