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Comparison of MR-based attenuation correction and CT-based attenuation correction of whole-body PET/MR imaging
David Izquierdo-Garcia1, Stephen J Sawiak, Karin Knesaurek
1Translational and Molecular Imaging Institute, Mount Sinai School of Medicine, 1, Gustave L. Levy Place, New York, NY, 10029, USA.
Purpose:
The objective of this study was to evaluate the performance of the built-in MR-based attenuation correction (MRAC) included in the combined whole-body Ingenuity TF PET/MR scanner and compare it to the performance of CT-based attenuation correction (CTAC) as the gold standard.
Methods:
Included in the study were 26 patients who underwent clinical whole-body FDG PET/CT imaging and subsequently PET/MR imaging (mean delay 100 min). Patients were separated into two groups: the alpha group (14 patients) without MR coils during PET/MR imaging and the beta group (12 patients) with MR coils present (neurovascular, spine, cardiac and torso coils). All images were coregistered to the same space (PET/MR). The two PET images from PET/MR reconstructed using MRAC and CTAC were compared by voxel-based and region-based methods (with ten regions of interest, ROIs). Lesions were also compared by an experienced clinician.
Results:
Body mass index and lung density showed significant differences between the alpha and beta groups. Right and left lung densities were also significantly different within each group. The percentage differences in uptake values using MRAC in relation to those using CTAC were greater in the beta group than in the alpha group (alpha group -0.2 ± 33.6%, R(2) = 0.98, p < 0.001; beta group 10.31 ± 69.86%, R(2) = 0.97, p < 0.001).
Conclusion:
In comparison to CTAC, MRAC led to underestimation of the PET values by less than 10% on average, although some ROIs and lesions did differ by more (including the spine, lung and heart). The beta group (imaged with coils present) showed increased overall PET quantification as well as increased variability compared to the alpha group (imaged without coils). PET data reconstructed with MRAC and CTAC showed some differences, mostly in relation to air pockets, metallic implants and attenuation differences in large bone areas (such as the pelvis and spine) due to the segmentation limitation of the MRAC method.
Insights
This study compared MR-based attenuation correction (MRAC) with CT-based attenuation correction (CTAC) in PET/MR imaging. MRAC showed good performance but had limitations with implants and bone, with higher variability when MR coils were present.
Area of Science:
- Medical Imaging
- Nuclear Medicine
- Radiology
Background:
- Combined PET/MR scanners offer advanced imaging capabilities.
- Accurate attenuation correction is crucial for quantitative PET imaging.
- CT-based attenuation correction (CTAC) is the current gold standard.
Purpose of the Study:
- To evaluate the performance of the integrated MR-based attenuation correction (MRAC) on a whole-body PET/MR scanner.
- To compare MRAC with CTAC for attenuation correction in PET/MR imaging.
Main Methods:
- 26 patients underwent both whole-body FDG PET/CT and PET/MR imaging.
- Patients were grouped based on the presence (beta group) or absence (alpha group) of MR coils during PET/MR.
- PET images reconstructed with MRAC and CTAC were compared using voxel-based and region-based analyses.
Main Results:
- MRAC showed an average underestimation of PET values by less than 10% compared to CTAC.
- The beta group (with MR coils) exhibited increased PET quantification and variability.
- Differences were noted in areas with air pockets, metallic implants, and large bone structures due to MRAC segmentation limitations.
Conclusions:
- MRAC is a viable alternative to CTAC, though with some quantitative differences.
- The presence of MR coils impacts PET quantification accuracy and variability.
- MRAC's segmentation limitations affect accuracy in specific anatomical regions and with implants.
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