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Motion-resolved and free-breathing liver MRF
Peng Cao1, Zuojun Wang1, Chenyang Liu2
1Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong, China.
Purpose:
To develop a motion-resolved and free-breathing liver magnetic resonance fingerprinting (MRF) protocol.
Methods:
The deformation maps were obtained from the first singular image of MRF data. The reconstruction method enforced the consistency of the MRF data with the deformation maps by adding the deformation maps to the encoding matrix. A sliding window reconstruction was inherently assumed, with a window size of 60 repetition times (TRs) and a step size of 30 TRs. L1 wavelet regularization was applied to reduce the undersampling artifact. MRF was tested on four healthy volunteers with parameters: 13 s/slice, 0.39 s/frame, and 33 time frames/slice.
Results:
For measuring the accuracy of the deformation map, the typical normalized root mean square error (NRMSE) of the first singular image after motion correction was 0.19. In the sagittal scan, the liver T1 and T2 were 808.7±96.8 ms and 52.7±11.6 ms, respectively. They agreed with our previously reported values, i.e., T1 = 759 ms and T2 = 51 ms at 3 T, using free-breathing liver MRF. Compared to breath-hold MRF, the NRMSEs for T1 and T2 maps (without considering vessel pixels) from the proposed method were 0.13 and 0.18, respectively.
Conclusion:
We demonstrated a motion-resolved MRF with a nominal frame rate of 2.5 Hz for free-breathing liver imaging.
Insights
This study presents a new motion-resolved magnetic resonance fingerprinting (MRF) method for free-breathing liver imaging. The developed protocol achieves accurate T1 and T2 mapping, overcoming motion artifacts in liver scans.
Area of Science:
- Medical Imaging
- Biophysics
- Radiology
Background:
- Liver magnetic resonance fingerprinting (MRF) is crucial for tissue characterization.
- Free-breathing techniques are desirable to improve patient comfort and reduce scan time.
- Motion artifacts can significantly degrade the quality of liver MRF data.
Purpose of the Study:
- To develop and validate a motion-resolved and free-breathing liver MRF protocol.
- To enable accurate T1 and T2 mapping of the liver during free breathing.
Main Methods:
- Deformation maps were derived from MRF data and incorporated into the reconstruction.
- A sliding window reconstruction with L1 wavelet regularization was employed.
- The protocol was tested on four healthy volunteers with specific imaging parameters.
Main Results:
- The developed method achieved a nominal frame rate of 2.5 Hz for motion-resolved imaging.
- Accuracy of deformation maps was validated with a normalized root mean square error (NRMSE) of 0.19.
- T1 and T2 values obtained were consistent with previous reports, showing low NRMSEs (0.13 for T1, 0.18 for T2) compared to breath-hold MRF.
Conclusions:
- A motion-resolved MRF protocol for free-breathing liver imaging was successfully demonstrated.
- The method effectively corrects for motion, enabling accurate liver parameter quantification.
- This technique holds promise for improved liver MRI diagnostics without breath-holding requirements.
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