Simulator validation using physical flow phantoms
One of the most important tasks of the project was validation of the designed simulation system.
This experiment was performed using physical phantoms of blood vessels, blood-mimicking fluid, and
specialized MR-compatible pump manufactured by Shelley Medical Imaging Technologies.
The flow phantoms set used in the project is primarily dedicated to MR scanners calibration and standarization.
The details of the conducted experiments are given in this article.
In the figure below, measured images can be compared against the simulated ones obtained for the digital phantoms,
whose geometry was adusted to the physical ones. The corresponding images were compared quantitatively by calculating a
correlation coefficient and RMS error. The obtained results (see the table below) as well as visual inspection of the images lead to
a conclusion, that the designed framework is capable of synthesizing realistic MRA images, to a large extent consistent with the measured data.
he synthesized images contain much of information found in the real ones. The most important image features reproduced in the performed simulations are as follows:
parabolic profile of the signal in regions of laminar flow,
signal void on slab borders,
specific flow patterns after stenoses,
higher signal on vessel walls than in the lumen in the channels with reverse flow direction.
Example real and simulated for the relevant physical and digital flow phantoms TR/TE/FA = 27/4.7/15° [ms/ms/-].
Quantitative comparisom of real and simulated images.
Phantom
|
Flow rate [ml/s]
|
Correlation coefficient
|
RMS error
|
U-band
|
2.5
|
0.927
|
11.52
|
4.6
|
0.904
|
11.57
|
10.0
|
0.811
|
13.24
|
50%-stenosis channel
|
2.5
|
0.918
|
12.01
|
4.6
|
0.911
|
11.89
|
10.0
|
0.781
|
16.75
|
75%-stenosis channel
|
2.5
|
0.897
|
13.05
|
4.6
|
0.901
|
12.06
|
10.0
|
0.875
|
13.97
|
|