(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To investigate whether BLADE-based DW-MRI can be used to replace EPI-based DW-MRI in head and neck MRI scans, by evaluating geometric distortion parameters.
Methods: MR imaging was performed on a Siemens 1.5T MR scanner with two 4-channel large flex phased-array coils and spine coil. Phantom measurements were performed using the quantitative imaging biomarkers alliance (QIBA) DWI phantom at 0 °C. DW images were acquired using single shot EPI (SSEPI) DWI, readout segmentation of long variable echo-trains (RESOLVE) DWI, and BLADE DWI. As a measure of image geometric distortion, including compression/dilation, shear distortions, and image shift factors were calculated and compared with gold standard CT images. Three volunteer measurements were also performed and all images were exported to Velocity software. Geometric distortion parameters and ADC values were analysed looking at the following head and neck regions of interest (ROI): salivary glands, and tonsils. T2-weighted images were used as reference for geometric distortion evaluation. All analyses were executed with JMP Pro software.
Results: DW images acquired using BLADE technique showed no or minimal geometric distortions. In phantom experiment (Figure 1), the layer vials from inner layer to outer layer on the diffusion weighted image became prominently distorted on the SSEPI-DWI and RESOLVE-DWI images, while BLADE-DWI image consistently showed less distortion evaluated by the overall effects of the compression/dilation factor, sheerness factor, and image shift factor. No significant difference in ADC values was observed between the three DWI techniques, however BLADE-DWI lead to a reduced SNR in all vials. In volunteer studies (Figure 2), ROI-based overlap analysis of the salivary glands and gross tumour volumes were less distorted for BLADE-DWI than that of EPI-based DWI.
Conclusion: The BLADE-DWI demonstrated excellent geometric accuracy compared with the EPI-based DW-MRI. Therefore, BLADE-DWI is expected to improve target volume delineation for head and neck radiotherapy.
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