Fig 1.
Illustration of the inflow effect.
Spins staying within the slice between applications of RF pulses (in black) will not have attained Boltzmann equilibrium (whose magnetization is ); spins entering into the slice (in red) which have not been tilted are saturated (whose magnetization is M0); spins entering between the π/2 pulse and acquisition (in blue) will not be involved in the detected signal (whose magnetization is M0 ∼ 0).
Fig 2.
Spin Echo Multi Slice (SEMS) sequence.
The upper part of the figure illustrates the inflow measurement depending on the slice location and the slices selection order. The lower part of the figure shows the RF pulse sequence of the SEMS sequence available on the commercial Varian MRI.
Fig 3.
In presence of a bidirectionnal flow () the second slice of flip will be sensitive to the positive direction inflow (
) while the second slice of flop will be sensitive to outflow (
).
Fig 4.
The Aladdin pumping device pushes the water from the syringe into a silicone tube forming a loop. The silicone tube crossed by opposite directions water flows is inserted within the birdcage coil into the MRI magnet.
Fig 5.
The tomato plant is installed inside the MRI magnet. The external part of the plant is enlightened by the LED panel.
Fig 6.
Flip-flop MRI sequence acquisition.
From left to right: flip sequence, flop sequence and substracted image (flip − flop). Experimental conditions: flowing water in a 3mm inner diameter silicone tube, vmean = 120μm/s, TR = T1/2 = 1.23s, TE = 15ms, FOVREAD = 20mm, FOVPHASE = 20mm, NREAD = NPHASE = 128, Thk = 1mm, 4 Slices and Tacq = 2 × 2min38.
Fig 7.
Right figure: at 10μm/s and left figure: 50μm/s. The following parameters were used: TR = 1.2s, TE = 15ms, FOVREAD = 40mm, FOVPHASE = 40mm, NREAD = NPHASE = 256, Thk = 0.5mm, 2 slices, AVG = 2 and Tacq = 2 × 10min14.
Fig 8.
a) A segmentation is applied on a region crossed by an assumed monodirectional flow. b) The formula given by Eq (16) is applied to the set of TR experiment to get the best vmax fitting value (here, 0.178mm/s while the expected value would be 0.2mm/s). c) The velocity scale can be added to the flow image.
Fig 9.
Illustration of xylemian sapflow imaging on tomato stem.
a) Anatomical image acquisition (TR = 1.2s, TE = 15ms, FOVREAD = 40mm, FOVPHASE = 40mm, NREAD = NPHASE = 256) b) Superimposition of the anatomical acquisition (background) with the flow acquisition (only the active xylematic tissues appear) c) Zoom on an active xylematic tissue region showing an higher intensity at the center of individual xylematic tissues.