- Poster presentation
- Open Access
Method for correcting respiratory artefacts in parallel-accelerated first-pass myocardial perfusion imaging
© Fair et al.; licensee BioMed Central Ltd. 2014
- Published: 16 January 2014
- Myocardial Perfusion Imaging
- Coil Sensitivity
- High Acceleration Factor
- Biomedical Research Unit
- Artefact Score
Myocardial first-pass perfusion (MPI) requires single-shot imaging of multiple slices per cycle. Breath-holding supports advanced high-resolution MPI methods, but tolerance to respiratory motion is desirable. Respiratory misregistration can induce aliasing artefacts by inaccurate coil sensitivity calibration, particularly at higher acceleration factors and during stress hyperpnea. Coil calibration can be adapted for respiratory motion, but autocalibration ("integrated") methods limit acceleration, and temporal coil-calibration methods may reduce SNR or cause temporal smoothing. We evaluated a motion-tracking modification of "prescan" parallel imaging specifically for MPI.
To compare the conventional and new methods, rest MPI was acquired in 20 consented patients referred for late-enhancement imaging (0.1 mmol/kg GBCA). Patients were asked to breathe "slowly and deeply" during MPI to mimic potentially increased motion due to stress (Cartesian FLASH, 2.6 × 2.6 × 10 mm, GRAPPA rate 4, 3 SAX slices/cycle). The new method repeats coil prescans over the range of free-breathing motion ("Multiple Free-breathing Prescans", MFP) before acquiring MPI. For each reconstructed image, MFP aimed to use a prescan at the closest respiratory position. For this respiratory position-matched prescan selection, the MPI image was initially reconstructed using any of the prescans. The anterior chest wall location in this potentially artifactual image was compared with its location in every prescan, using a semi-automatic edge-detection algorithm. This enabled selection of the optimal coil prescan for each image of a final GRAPPA reconstruction (labeled MFP). The initial MPI image using a Single Conventional Prescan for its GRAPPA reconstruction (labeled SCP) was compared with MFP by randomised blinded scoring of parallel artefact (0 = none to 4 = non-diagnostic). In 5 further patients, MFP was compared with other coil calibrations (SCP, Integrated, Temporal) at increasing accelerations (R 2-6) by retrospective subsampling of full k-space MPI scans. The root-mean-square difference error (RMSE) over the FOV compared accelerated vs fully-sampled images.
The MFP method by semi-automated image-based selection of a position-matched prescan reduces parallel imaging aliasing artefact in free-breathing MPI.
Biomedical Research Unit, National Institute for Health Research.
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