Figure 7
3D respiratory traces obtained from two volunteers by extracting and combining displacements from two orthogonal image navigators, respectively. Left: subject 1 with highly regular breathing pattern, recorded during the acquisition of spectra in Fig. 8a. Right: subject 2 with irregular breathing amplitudes and intricate patterns (according spectra: Fig. 8c,d). First row: motion curves in patient coordinates (a,d). Second row: curves decomposed into their principal directions (b,e). ‘sv 1’ denotes the individual principal component of the motion trace in patient coordinates (LR,AP,HF). Third row: to highlight the extent of voxel misalignment during motion, we demonstrate the overlap of the initial and the displaced magnetic resonance spectroscopy (MRS) voxel for single voxel spectroscopy (SVS) with 75 ml voxel size (c) and magnetic resonance spectroscopic imaging (MRSI) with 9.5 ml voxel size (f) in the third row. On average 70% and 41% of the nominal voxel volume coincides with the desired location over the whole measurement of \(\approx\) 11 min. In (f) the position of the initial breath hold is never properly matched again, resulting in a poor yield of only 41% overlapping volumes.
