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Tips for Quantitative Flow measurements

Application Tip
Geerts, Liesbeth Philips Healthcare
Nijenhuis, Marco Philips Healthcare
van den Heuvel, Martina Philips Healthcare

Tip 1: Perform fast Q-Flow scans with TFE in breath-hold technique

From Release 11 and Release 1.2 on it is possible to perform fast, reliable breath-hold Q-Flow scans with the TFE technique.

Tip 2: Plan perpendicular to the vessel of interest for reliable flow quantification

Plan perpendicular to the vessel to obtain reliable estimates of both the velocity profile (V) and the vessel area (A).

ApTip MN&LG planning perpendicular
ApTip MN&LG planning perpendicular

Tip 3: Scan with sufficient spatial resolution

At least 10 pixels within the vessel are necessary for reliable flow quantification. For lower resolutions, flow information may be affected by partial volume effects. Especially in smaller vessels this may be an issue.

Tip 4: Use a high temporal resolution for reliable flow quantification

Use a high temporal resolution to detect a flow curve, i.e. set the number of phases high enough. If the number of sample points ( # phases) is too low, the real flow curve cannot be displayed accurately enough, see the schematic drawing below.

 

As a rule of thumb you have to use scans with at least 12 to 15 phases.

 

ApTip QFlow MN&LG schematic drawing
ApTip QFlow MN&LG schematic drawing

Tip 5: Position the ROI correctly

Measuring amount of blood (flux)

If the aim is to measure the amount of blood flowing through a vessel (flux), make sure that the whole vessel is included in the ROI (left image). In this case, the area of the ROI is larger and the average velocity is lower, but the flux (the area multiplied by velocity) remains unchanged.

 

Measuring maximum velocity

If the aim is to measure the maximum velocity, avoid including noise pixels located near the vessel wall. Make sure that the ROI is located inside the vessel (right image). In doing so, the minimum and maximum values represent pixel locations inside the vessel.

ApTip QFlow MN&LG ROI size
ApTip QFlow MN&LG ROI size

Tip 6: Use the non-interpolated overlay with ViewForum post-processing

Within the ViewForum environment a non-interpolated overlay can be generated to determine more accurately which voxels need to be included or excluded for analysis.

Tip 7: Draw contours on a systolic modulus image with auto contour detection

When using auto contour detection, start drawing contours on a systolic modulus image. The algorithm will adapt better to the contours from the other phases.

Tip 8: Change units for slow flow measurements

For analysis of the aqueduct (slow flow), units have to be changed to suit the need. This can be done under settings.

 

Velocity:  -> mm/s

Flux:       -> mm3/s

Area:     -> mm2

 

Tip 9: Perform in-plane flow measurements to detect flow directions

In-plane flow measurements can be used to detect flow directions.

 

Flow in the positive off-center direction will show up white.

Flow in the negative off-center direction will show up black.

 

Example: An in-plane flow measurement is performed with a flow sensitivity in the RL direction. Flow from right to left (RL) will show up bright, flow from left to right will show up dark.

In-plane flow measurement Flow sensitivity: AP, slice thickness 15 mm.In-plane flow measurement Flow sensitivity: RL, slice thickness 15 mm.
In-plane flow measurement
In-plane flow measurement
Flow sensitivity: AP, slice thickness 15 mm.
Flow sensitivity: RL, slice thickness 15 mm.


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Apr 28, 2005

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Application Tip
Achieva 1.5T, Achieva 3.0T, Intera 0.5T, Intera 1.0T, Intera 1.5T, Intera 3.0T
Release 1, Release 10, Release 11, Release 9
Abdominal MRA, Brain, Extracranial MRA, Peripheral MRA, Thoracic MRA, Vascular
 

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