There are two methods for cropping images opened in Aivia.
The first is found in the Top Menu under Edit --> Crop. This will open the crop dialog which allows you as the user to select the range of frames from a z or t series as well as the interval between which frames to keep (i.e., and interval of 1 will keep every frame while and interval of 2 will keep every other frame). On apply, this will produce a working image that has only the frames determined from the range an interval supplied in the crop dialog.
The other method for cropping involves using the ROI tool to select a specific region of the current field of view and cropping outside of that field. To do this, go to the Top Menu and select View --> ROI Tool. Then use the cursor to draw a ROI around the area that you'd like to keep. If your ROI doesn't come out perfect at first you can resize it by clicking and dragging the anchor points on the bounding box. The ROI itself can even be moved translationally within the image. Once the ROI is the correct dimensions and in the correct location, right-click on it to bring up the ROI Context Menu and select Crop ROI. This will produce a working image with only the selected ROI in the Image Explorer workspace.