Maximum intensity projection (MIP) imaging using slice‐stacking MRI a)

Purpose: To evaluate the feasibility of acquiring maximum intensity projection (MIP) images using a novel slice‐stacking MRI (SS‐MRI) technique. Methods: The proposed technique employed a steady state acquisition sequence to image multiple axial slices. At each axial slice, the scan is repeated throughout one respiratory cycle. Four objects (small, medium, and large triangles, and a cylinder) moving with a patient breathing trajectory were imaged repeatedly for six times using the slice‐stacking MRI and 4D‐CT.MIP SS ‐ MRIandMIP 4 D ‐ CTwere reconstructed. The internal target volume (ITV) was segmented for each object on the six scans and compared betweenMIP SS ‐ MRIandMIP 4 D ‐ CT. The medium triangle was also imaged with various motion patterns using slice‐stacking MRI, 4D‐CT, and sagittal cine‐MRI. The corresponding MIP images were reconstructed and volume/area measurements were performed and compared between different imaging methods. Three healthy volunteers underwent the slice‐stacking MRI and sagittal cine‐MRI scans. A region of interest (ROI) was selected and contoured for each subject in bothMIP SS ‐ MRIandMIP cine ‐ MRI. The area of the selected ROI was computed and compared. Results: Volume comparison betweenMIP SS ‐ MRIandMIP 4 D ‐ CTshowed statistically insignificant ( p > 0.05 in all cases) difference in the mean ITVs for all four objects. For the study of the medium triangle with multiple motion patterns, there was a good agreement in the measured ITVs betweenMIP SS ‐ MRIandMIP 4 D ‐ CT( p = 0.46 , correlation coefficient = 0.91 ), with a mean difference of 1.4 % ± 4.4 % . The area measurements betweenMIP SS ‐ MRIandMIP cine ‐ MRIalso showed good agreement ( p = 0.47 , correlation coefficient = 0.97 ), with a mean difference of 0.2 % ± 2.9 % . For the healthy volunteer study, the average difference in the area of selected ROI was − 2.5 % ± 2.5 % betweenMIP SS ‐ MRIandMIP cine ‐ MRI. Conclusions: These preliminary results showed good agreement in volume/area measurements between the slice‐stacking MRI technique and 4D‐CT/cine‐MRI, indicating that it is feasible to use this technique for MIP imaging.