Prostate images acquired with an endo-rectal coil usually exhibit bright signals near the coil. To correct for this brightness, use the PACC program to apply an analytical surface coil intensity correction algorithm to the high\u0002resolution images. This program allows you to determine the location of the endo-rectal coil relative to the uncorrected images, thereby providing the coil location to the correction algorithm.
Considerations
CAUTION
Post processing results may be affected by the presence of MR Conditional implants. Consider the following related to post-processing MAVRIC SL images on your MR , PACS or AW systems: If an image includes susceptibility artifact, such as from MR Conditional metal implants, measurements made on the image may be incorrect due to distortion of actual physical locations.
Step-by-step instructions
Navigate to the Image Management work area.
In the Patient List, select the prostate examination and a series you want to correct with the PACC program.
Click PACC from the Session Apps List.
The PACC screen has the following areas: three image viewports, a list of series in the selected exam, and a simple control panel.
If you selected a series from the Patient List, two images from that series are displayed in the upper PACC viewports.
Do not run the PACC tool and the Viewer or Mini Viewer at the same time. You must quit the PACC program before starting the Viewer or Mini Viewer (and vice versa).
Click the upper-left viewport to make it active, and as necessary, click + (next) and - (prior) to select the sagittal image that you will use to locate the endo-rectal coil in the sagittal plane.
Display the FSE T2-weighted axial/oblique coil locator image in the upper-right viewport.
Click anywhere in the upper right viewport.
As necessary, click + (next) and - (prior) to select the axial/oblique image that you will use to locate the endo-rectal coil in the axial plane.
Make sure one of the coil locator images is in the axial/oblique plane and the other is in the sagittal plane.
You can pan, zoom, and adjust the window and level of the images in the three display windows by clicking inside the display windows and dragging the mouse.
Pan: When selected with the Set Points/Pan option, click and drag to move the image within the viewport. Pan is disabled when the Set Points/Pan is set to Set Points.
Zoom: Right-click and drag up and down to adjust the magnification.
Window width (contrast): Middle-click and drag left and right to adjust the contrast. The current window width value is displayed in the lower left corner of the viewport.
Level (brightness): Middle-click and drag up and down to adjust the brightness. The current window level value is displayed in the lower left corner of the viewport.
Note:
The pan, zoom, window width and level settings for a particular display window are propagated to all the other images in the series. If you page to a different exam or series, then the pan, zoom, and window width and level settings return to their default values.
Once you are satisfied with the image displays, choose two coil location points on each of the images in the upper viewports.
The goal is to locate the top and bottom of the endo-rectal coil on the sagittal images, and to locate the left and right extent of the coil in the axial/oblique image. Generally, the coil will be close to the regions of the anatomy with the highest signal intensity.
There are other common features in the images that you can use to guide the placement of the locator points.
Set the Set Points/Pan option to Set Points to enable the coil locating mode in the upper viewports.
Coordinates of the locator cursors or points are listed in the four entry fields to the left of the PACC interface. You can click Clear to erase the entries.
Click on an image to place a locator cursor on the image. While it is difficult to grab and drop a locator cursor once deposited, it is easy to click on the image and drag the locator cursor to the desired location.
Locate the coil in the sagittal plane. The top of the coil often corresponds to a short, dark curved line that extends from the rectum in to the tissue. A similar dark curved notch extends from the rectum into the tissue near the bottom of the coil. Place the locator cursors near these coil indicators. It is a good idea to place the cursors in the rectum rather than on the tissue or even close to the tissue. The less aggressive placement of the locator cursors limits the possibility of over correcting the signal intensity near the coil - remember that 60 to 70% of prostate cancers are found in the region of the prostate nearest the coil.
In the axial/oblique images, the coil edges correspond to indentations into the tissue (the indentations look like “horns”) that are surrounded by the bright regions in the anatomy. Click and drag and drop the locator cursors near the indentations. As with the sagittal locator cursors, it is better to place the cursors within the rectum rather than on the tissue or even near the tissue.
An example of the cursor locator placement is shown on the PACC screen.
Use the bottom viewport (Choose One or More Series to Correct) to select one or more series that you want to correct.
Click to choose one series or to choose the first of several.
Simultaneously press Shift and click to choose all of the series from the first series to the current choice.
Simultaneously press Ctrl and click to add or delete a series, one-at-a-time.
When you are satisfied with your coil location points and series selections, click Correct Series.
The correction may take some time, so be patient. While a correction is in progress, the PACC screen will not respond to any actions except Cancel.
The status bar displays correction status messages. The lower right Corrected Image window displays each of the images after they are corrected. Sometimes the correction algorithm executes two passes through a series.
If the correction completes successfully, the message "Correction Successful" appears in the status bar. Otherwise an error message accompanied by a pop-up error message window is displayed.
You can browse the corrected images in the lower right viewport by right-clicking on the viewport. Click + (next) and - (prior) to page through the corrected images. The lower right viewport will only display images from the last series that was successfully corrected.
Click Quit to exit the PACC screen.
If you are correcting images you must click Cancel and Quit to exit.
