Example of zoom

Let's try to consider an example of using zoom in analyzing a study.

First consider the usual activity. You want to look at a tumor in more detail so you change the gray scale by dragging the cursor over the PET or CT to change its gray scale. UP-down changes the base line. Left right changes the contrast. The other common thing is to change the slice you are looking at. The mouse wheel does this. Many times the CT has more slices, such that if you scroll on the PET you may not see some of the CT slices. Thus moving the wheel over the CT image will go one slice at a time on the CT, while perhaps leaving the same PET slice for 2 CT slices.

Now let's consider the zoom. It can happen that you want to see part of the study in greater detail than it was originally collected. You press on the Zoom button, or use the keyboard shortcut z. Now the mouse has a different meaning. The wheel changes the zoom value, increasing or decreasing the zoom. The mouse drag changes the pan, because at high zoom what you may want to see may be off screen.

Now you want to see a neighboring slice. Do you need to leave the zoom? The answer is a definite "No". While it is true that the mouse wheel won't get you a new slice (it will change the zoom), the arrow keys as well as PgUp and PgDn will change the slice displayed.

So, one option is to remain with the Zoom button active where you can change the zoom and the pan. Another option is to free the Zoom button in which case the wheel and drag will return to their original functions. In this case the zoom value and the pan values will remain fixed at whatever values they had when you freed the Zoom button. To change the zoom, you will need to press the Zoom button again.

Thus you are free to pick whatever most suits your way of looking at studies. If it is just changing slices, the arrow keys are probably best. If you want to change the gray scale, it is probably best to free the Zoom button. For a more detailed explanation see scrolling.

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