An introduction to 4D View (Version 5.0)HP Dietz

This tutorial gives an overview of the functionality of the software 4D View forpelvic floor imaging and takes first- time users through the basic steps ofperforming an analysis in patients with lower urinary tract symptoms and / orpelvic floor dysfunction.

After installation on a PC running Windows 2000 or XP / XP Professional,preferably a Pentium 4, a screen showing the program version becomes visible.Click on this screen. Via the File pulldown menu on the left (see Fig.1, longarrow), any GE Kretz compatible volume data file can be opened. Incidentally,the File menu also allows for export of bitmaps (‘Export graphic’) and AVIvideoclips (‘Export 4D Img. Cine Sequence’). Most options in the ‘File’ menu arealso accessible via a vertical bar of icons on the far left of the screen (shortarrow).

The dataset downloaded via the ‘trial volume’ link on the website should beopened by browsing via ‘Open’. It is a single static volume dataset of about 5 MB,obtained at rest. This should result in appearances similar to Figure1.

Figure 1: Standard orthogonal views on 4D View.

The black workspace shows the three orthogonal planes A (midsagittal, top left),B (coronal, top right) and C (axial, bottom left) plus a rendered volume (bottomright). The rendered volume shows a semitransparent representation of all‘voxels’ (volume pixels) in the ‘region of interest’ or ‘ROI’, i.e., the box visible inthe A and B planes (thin arrows). The green line at the top of the box represents

the rendering direction, i.e., the direction in which the rendering algorithmanalyses the volume data. This function is accessible via the ‘Settings’ pulldownmenu (‘ROI direction’) in case you want to explore the effect of altering therendering direction.

We’ll start with some simple 2D measurements. In order to optimise for this,please click on the ‘Sectional Planes’ button (Fig. 2, arrow) in the ‘Visualization’menu on the far right. This should make the rendered volume and the region ofinterest box disappear- see Figure 2.

Figure 2: Sectional planes.

You can manipulate all three planes arbitrarily - either by clicking on the imageitself (e.g. the A plane), or by using the three control sliders immediately belowthe workspace (‘Rotation X’, ‘Rotation Y’, ‘Rotation Z’). Moving the mouse cursorover the A plane and left- clicking changes your arrow into a small icon. This iconwill vary depending on how close to the centre of the image (identified by a smallyellow dot in the plane that’s currently active) you are. Please try and drag thisicon and observe the effect on your screen. Rotating the A plane image mayresult in appearances such as in Figure 3, or (more likely) something a lot moreconfusing.

Figure 3: Rotating the A plane.

Once you are well and truly lost, please click the ‘Init’ button (Fig. 3, long arrow)to revert to the appearances in Fig. 2. The three buttons to the left of ‘Init’,incidentally, allow you to select the active plane without clicking on the plane inquestion. (Tip: The ‘Init’ option will come handy whenever appearances on yourscreen deviate markedly from the figures given in this chapter - which is likely tohappen many times. However, if you’d rather not lose whatever you’ve done untilthat point in time - e.g. altered image settings - the ‘Orient. Help’ button (smallarrow) under ‘Init’ may be more useful, giving you a graph of the location of yourcurrently selected plane in the entire volume).

In order to perform some basic measurements in the A plane, let’s enlarge thetop left hand part of the workspace. Please click on the right hand button under‘Display Format’ which allows the currently active plane (which should be the Aplane) to fill the workspace. The screen should now look like Figure 4.

If your image should not be exactly centred (i.e., if the A plane does not show theurethra well, use the ‘Ref slice’ control for adjustment (short arrow in Figure 4).Once you’re happy with the appearance of your A plane, please click on‘Measure’ (Figure 4, long arrow). The 4D View measurement package will takesome seconds to load. As there currently is no application ‘Pelvic Floor’ yet we’lluse the ‘Generic’ menu. This should give you the appearance shown in Figure 5.

Figure 4: Measurements.

By clicking on ‘Generic Dist’ (Fig. 5, long arrow) and ‘Dist 2 point’ (short arrow)you should be able to measure e.g. bladder neck position relative to thesymphysis pubis (see Figure 5) and detrusor wall thickness (not that easy hereas the bladder is completely empty). By clicking on ‘Generic angle’ and ‘Angle 2line’ you should be able to measure any angle you may want to determine, e.g.retrovesical angle or the levator plate angle.

Figure 5: Measuring distances.

In order to perform measurements in the C plane you need to click ‘Main Menu’(bottom right corner). Rotating the A plane (see Figure 3) will change theappearances of the C plane until the C plane represents the minimal dimensionsof the hiatus. Experiment with moving the central marker in the A plane up / downand left / right before rotating. (Tip: If a small double-sided arrow comes upinstead of the bulls-eye, you’ve clicked on the image too far from the centralmarker). Remember the ‘Init’ button: it will likely take several attempts until youhave appearances similar to Figure 3. Once this is the case, select the C planeand click the right hand button under ‘Display Format’ in order to enlarge the Cplane. Then rotate the C plane by clicking on it about 1-2 cm from the centralmarker, and drag the image until the hiatus assumes appearances as in 6. Youmay also drag the control ‘Magn.’ under the right hand corner of the work area inorder to make sure that the feature you want to measure fills the screen (Tip: Ifyou can’t see the ‘Magn.’ control you’re probably not in the Main Menu. You canalways get there by clicking the ‘Main Menu’ button. If you can’t see that button,you’re already there).

Once you’re back in the ‘Measure’ menu you should see an image similar toFigure 6. Now you should try and measure an area, e.g. the hiatal area as inFigure 6, by clicking ‘Generic Area’ and ‘Area Trace’. (Tip: At this stage you’ reprobably cursing your track-pad or mouse, and searching frantically for a decentmouse pad. A graphic tablet, if available, is likely to give superior results).

Figure 9.6: Measuring angles.

At this stage let’s try and optimise image quality a bit further. Please click ‘MainMenu’ in the bottom right hand corner and select ‘Image settings’ next to the‘Measure’ button. This should give you the appearances shown in Figure 7.

Figure 7: Optimising image quality.

Please experiment by dragging the controls ‘Bias’ and ‘Pos’ until you’re happywith the image (Figure 7, long arrow). There also is an option ‘SRI’ whichimproves resolution by speckle reduction (short arrow). SRI comes in six steps;the author usually selects steps 4 or 5. (Tip: SRI may result in irritating whorl-likeartefacts, especially when processing volumes obtained by older systems. It’s amatter of trial and error).

While we’re in the C plane, let’s also try another recent innovation, ‘TomographicUltrasound Imaging’. In the Main Menu you’ll find a button ‘TUI’, situated in the‘Visualisation’ submenu on the right (Figure 8, long arrow). Clicking on this buttonwill give you the standard TUI screen, containing a reference plane in the top lefthand corner and seven axial slices at predetermined intervals filling the rest ofthe workspace. It should look approximately like Figure 8. These intervals can beadjusted with the ‘TUI distance’ control (short arrow). You may also want toincrease the number of slices via ‘Slices: -, +’ and change which ones are shownin the workspace by using ‘TUI slices’, ‘Prev’ and ‘Next’ in the bottom rightcorner.

Figure 8: Tomographic ultrasound imaging.

Congratulations!

You’ve come to the end of this short tutorial and should now have a fair idea ofwhat is possible using 4D View even with static volumes. Cine loops of volumes,i.e., true 4D imaging, requires datsets that are too bulky for download at thepresent time. Please contact me if you would like to take things further. I’d behappy to provide both the full version of the tutorial and training datasets.

Best wishesHP DietzSydney 2006