Chapter 11: Time Dependent Analysis(TDA) for Flow Analysis

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1 Chapter 11: Time Dependent Analysis(TDA) for Flow Analysis The optional Flow workflow performs quantitative flow analysis on phase-contrast MR images. It provides semi-automatic contour detection for the analysis of the blood flow in vessels. The parameters calculated include stroke volume, forward and backward flow volume, regurgitant fraction, absolute stroke volume, mean flux/velocity and stroke distance. Select an anatomical series and velocity series from a cardiac MR study, click Load and select the Flow workflow. Note: When non-supported flow data is loaded, a error message is displayed. Measuring the Flow in a ROI Draw a ROI on the anatomical data in one of the following ways: Create ROI Create threshold for all phases: Shift+click on the image. Edit ROI Freehand edit: Shift+drag, starting from the edge of the ROI, drag mouse across the area. Using the Nudge tool: Alt+drag The Flow Viewer Layout The top-left view shows the anatomical image. In the top-right view, the velocity map is displayed. ROIs in the velocity map correspond directly to the ROIs in the anatomical image. The bottom-left view shows a graph of the velocity inside each ROI, and the same values in text form are listed in the bottom-right view AQ-IN-USER-EN-4.4O

2 Aquarius intuition Client Chapter 11 The Color Bar The color appears on the left side of the anatomical image (see image at right). It shows which colors, when overlayed on the ROIs, represent velocity values at different phases. To see each phase, hold down the left mouse button and scroll up or down. Customizing the Color Bar To change the color map or create a customized color map, right-click on the color bar and select Load Color Map. The Color Template Editor is opened (see image at left). For instructions on using the color template editor, see Changing Color Maps on page 9-3. Window/Level Bar The window/level bar is located on the left side of the velocity map view. It shows the range of velocity values for the W/L setting. Capturing Text Results To capture the text results, right-click on the text view and select one of the capture options. If the results for all of the phases in the series can fit in the text view, the capture is complete. If there are more phases than can be displayed in the view, you will see the dialog shown at right. Click Yes if you want the entire text table to be captured in one image. The font size is decreased to the size necessary for it to fit. Click No if you want the text size to stay as it is. In this case, the text table is captured in more than one image. Features of the Graph You can display several kinds of information, and present it in different ways using the following features: AQ-IN-USER-EN-4.4O 11-2

3 Baseline Correction Baseline correction can be done in several ways. Select the preferred method from the baseline input menu at the bottom of the tool panel (see image at right). Drawing the ROI for baseline correction (one phase) 1. Make sure that the menu item selected is Draw ROI for the baseline correction (one phase), and then click the button. It changes to a dark blue color to indicate that it is selected. 2. Hold down the Shift key and draw a small ROI on an area of the anatomical image that has uniform color. The baseline is displayed at the bottom of the graph window: The same baseline correction is used for all phases. Drawing the ROI for baseline correction (all phases) This is performed the same way as you would to draw an ROI for baseline correction in one phase, but in this case, the baseline correction is calculated separately for each phase. To verify, scroll through the anatomical images. The vertical line in the graph view steps through each phase, and the baseline correction displayed at the bottom of the graph changes for each phase. Inputting the baseline correction value 1. Obtain an ellipse or other area mesaurement on a small area of the anatomical image that has uniform color. Measurement of uniform area Use this value as the baseline 11-3 AQ-IN-USER-EN-4.4O

4 Aquarius intuition Client Chapter Use the Mean value in the velocity map view as the baseline. In the image above, that value is Select Input the baseline correction value from the menu at the bottom of the tool panel. Or you can right-click on the graph and select Baseline correction. Either will open the Baseline Correction dialog. 4. Enter the mean value in the dialog. To apply the baseline correction to the text table, check the box labeled Apply baseline correction to values on text view in the tool panel. Moving the line on the velocity graph manually On the Velocity graph, click the horizontal pink line to move it up or down. The baseline correction appears in the bottom-left of the graph view (circled, at right). Note: One baseline correction value is applied to all phases. Displaying Different Graphs You can display the following graphs in the graph view: Flux, Area, Velocity, Max Velocity, Min Velocity, Peak Velocity and Standard Deviation. Zoom To zoom in the graph, click anywhere on the graph and drag the mouse in a horizontal direction. The area selected as you scroll turns white to indicate the zoom amount. The graph zooms in by a factor inverse to the width selected, so the more area selected, the smaller the zoom factor. To reset the graph to its original size, click the icon in the lowerleft corner. AQ-IN-USER-EN-4.4O 11-4

5 Invert Graph To invert the graph, right-click on one of the data points in the graph curve, and select Invert from the menu (see the image below) AQ-IN-USER-EN-4.4O