This page is a step by step guide to a basic use of the software FlowV1.4.
Flow Quick Start
The first thing you see when you launch the application is the main window.
In the "File" Menu, click on "Open Series".
Then Choose a directory containing a DICOMDIR file and click "OK".
For this example, we will use the anonymized data found on the TIDAM website.
A new window opens, showing all the images series contained in the directory previously selected.
For each series this window displays several informations, for example:
- the manufacturer and model of the MRI machine used to do the acquisition of theses series
- the patient's name
- the id and date of the study
- the type of the series, for example, for the selected series the type is "OS/I OMag" which means that this series contains Oriented Sup/Inf and Oriented Magnitude images.
- the velocity encoding for the Phase Contrast aquisitions.
- a preview of the first image of the selected series.
The images will be loaded in the main window. The twelve images on the left of the window show the different images of the series, you can navigate through all the images by using the "Sheet scrolling" slider below the images.
The "Position" and "Width" sliders are used to control the luminosity and contrast of the images. are used only for display and will have no incidence on the segmentation so you can play with these freely.
Below the sliders you can see a text area which contains additional informations about the loaded series.
Finally, on the right is displayed the current image of the series, which you can change by clicking on one of the images of the left panel.
Next we have to select the area of the image that we want to segment.
Go to the "Spectral Segmentation" menu and choose "region 16*16" (the 16*16 means we want to zoom on a region whose size will be 16 pixels by 16 pixels, if you want a bigger region feel free to try the other options of this menu).
A new "Flow Analysis" window opens. In the main window, the small area in the middle of the image with the black and white pixels is the aqueduct we want to segment, click on it.
The selected area should appear in the "Flow Analysis" window, if not, click again, on Mac and Linux, you may have to click several times for the window to gain focus.
As in the main window, you can use the sliders "Offset" and "Width" to adjust the luminosity and contrast of the images (note that the "Offset" slider of this window is the same as the "Position" slider of the main window).
Then, in the "Actions" menu, choose "Define ROI" and click on "Spectral Segmentation".
A default threshold for the segmentation will be automaticaly selected and the resulting mask will be displayed in the lower left image of the window.
You can adjust the threshold by using the "Threshold" slider in the top of the window.
Once the mask is displayed, click in the lower left image on the area that you want to keep for the final mask. You can click on several areas, they will add up in the top right image. For this example, we only need one area.
Note that, if you need to adjust the mask more precisely, you can left-click on the top-right image to add/remove pixels.
When you are done with the mask, click on "Apply Contour" in the "Actions" menu.
This will apply the mask to the selected series. You can check that the mask has been applied to the 32 cardiac phases of the series by clicking on one of the "Play" buttons in the top-right of the window. The button on the right is for playing phase contrast images, while the one on the left is for amplitude images.
Several curves are displayed:
- the velocities curves in the lower right image. The thickest one represents the maximum velocities, the dotted one is the minimum velocities and the last is the mean velocities.
- the flow curve in the lower left image
- the deplaced volume in the top-right image (integrated flow curve)
Since the flow and deplaced volume curves are computed from the velocities curves, errors in the velocities informations will induce errors in the calculated curves.
To prevent this kind of errors, we have to antialias the velocity curves and recalculate the resulting curves.
That is what we do next.
In the "Options" menu, choose "Antialiasing" and click on "90%".
The default is "0%", which means no antialiasing. Note that, if you want to tune antialiasing more precisely, you will have to go from 90% to 50% until you find the value that fits the most the series you are working with.
You can see that the curves are smoother.
We can now save our results.
In the "Levels" menu, select the level which corresponds to the area that you have just segmented, in our case CSF->Aqueduc.
This will automaticaly save our results.
Notice that, you can also enter the name of the level by clicking on "Other".
By default, the results are saved in the FLOW_DIR/idl71_rt/flux directory where FLOW_DIR is the directory where lies the executable of the Flow application. This can be changed in the "Save Place" option of the "File" menu in the main window.
You can now close the "Flow Analysis" window.
We will now visualize our results in a 3D view.
In the main window, select the "3D view" option of the "Windows" menu.
A new "3D Visualization" window opens in which the results of the current patient are automaticaly displayed.
You can rotate the 3D model by left-clicking in the left area of thewindow, right-click to pan and use the wheel to zoom in and out.
Next, we will add morphology images.
In the "File" menu, click on "Add Series".
This will open a window similar to the one we used to open our PC-MRI Series, except that you can only open amplitude series from this one (i.e. morphology images).
Select the "Sag T1 FLAIR" series and click OK.
You can see that a sagittal image has been added to the 3D view.
You can change the displayed morphology image by selecting the corresponding series in the tree in the top-right of the window, and then use the "Amplitude Image" slider.
To hide or show an image or a flow in the 3D view, you can right-click on it in the tree and select "Show/Hide".
Finally, you can click on the "Play" button next to the"Image Number" slider and watch the animation.