Thursday, September 15, 2005

Two, Four, Six, Eight,
This Is How We Mensurate!

\Men"su*rate\, v. t. [L. mensuratus, p. p. of mensurare. See Measure, v.] To measure. [Obs.]
Source: Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.

Now that we have that straight....

Measurement is one of the most tedious, yet critical operations we radiologists perform on our images. It is very important to know the size of various items, such as (unfortunately) tumors, and whether or not they have changed from the last time they were examined. As with other things in life, size is not the only important issue, and additional factors, such as angle or density might also need evaluation.

The early PACS GUI's had simple ruler tools. Click the button, point the cursor to one margin of the object in question, left-click-and-drag to the other margin, let go, and voila! The length in centimeters of the badness is produced, though often the number was plopped right over the lesion, just where you didn't want it.

Many of the newer systems put the numerical measurement somewhere else. I actually like the way ScImage does this to some extent. (That thud you felt was everybody in Los Altos fainting). You click and drag and then drag again to place the number wherever you want it to be. So far, so good, but sadly it doesn't stop there. ScI's PICOM viewer has tremendous state problems, i.e., you have to left click in each window or toolbar before it recognizes where you are and what you wish to do. With their version of the venerable ruler (magnificently represented on the tool bar by a line on the button), you can't let go without deliberate effort. Left click on the first point, then left click again on the second, then left click again to place the number which is (nicely, I might add) flagged to the line of measurement. Personally, I prefer the click and drag routine. Amicas does this, with a fixed-position numerical "flag". Now, neither lets you reposition the line of measurement. You can erase it, or with Amicas you can actually move the whole line, but you can't resize it. With Centricity, you can resize by selecting the arrow tool and then pointing at one end of your line. By the way, GE does something completely unacceptable with measurements: only two numbers are displayed on the screen at one time. If you have three (or thirty-seven, for that matter), you must use the arrow and point to the one you wish to see. GE says this is to keep the screen clear. BS. If I want thirty-seven measurements on my screen at once, that's my problem, and GE should not enforce it's will on me. But that's the way GE thinks.

Agfa has some good and bad elements in its ruler tool. You left-click and drag after toggling the tool "on", then you have the option to click on a grab-box in the center of the line that will let you drag the numerical measurement elsewhere if you wish. Good idea. But you have to right-click to drop the measurement, and two right-clicks drop the tool. Potential for problems with that. Agfa labels each measurement A, B, C, etc, which is helpful as there is no dotted line connecting the number to the line of measurement. GE uses numerals for this.

Now, here is my idea for the perfect ruler... I like the simple left-click-and-drag approach for the measurement itself, and I like the option to move the scalar somewhere else if desired. So, combine Amicas' and ScImage's approach to that point. It also would be nice if you could click a line with the ruler tool if you need to adjust it. Here is my great innovation....add magnification to the mix. As noted on an earlier entry, Agfa uses the mouse wheel to magnify within the zoom tool. How about enabling this functionality for the ruler? Amicas actually won't let you drop a line if it does not cover a sufficient distance (basically if you didn't move the mouse more than a few pixels), so how about giving you the ability to zoom in on the area of interest while still within the same ruler tool? I think this would work quite well. Who's going to be the first to implement it???

I'm going to ignore the angle tool. Most systems let you draw two lines in some fashion and then give the angle between them, useful for Cobb angle measurement. Amicas plans to implement this on the next release of LightBeam. I can't say I've noticed its absence.

The ellipse serves many purposes, mainly highlighting an area or giving the average density within that area. Once you get beyond the toggle mentality, I prefer Agfa's approach. Left-click for the center of the ellipse, left-click-and-drag for one axis, and again for the second. Until the tool is dropped with a right-click, the ellipse can be rotated and resized to your heart's content. The ellipse grows from the center, not an edge, which turns out to be more intuitive.

Any votes for my next tool-ish remarks?


Anonymous said...

Have you ever seen the ability to, once in measurement mode, make two clicks? The first on the starting point and the second on the end point. Then, your line and measurement appear. I forget where I saw it, but it seemed to be really easy. Same way for angles - 4 clicks and your angle appears. No dragging, and it is really fast and accurate. While in this mode you could still zoom as well. On the line itself appears a very small, non obstructive label referencing the measurement that appears in an organized manner off the image.

Dalai said...

What you describe is more or less how ScImage does it. While I like the final output it produces, this is the the ruler approach that can leave you hanging.... After the first click, the measurement line just flops and flails around until you click it somewhere. I prefer the Click-and-Drag thing personally.

Anonymous said...

What "Anonymous" describes might be found in several environments I have not personally worked with, but it is basically the method Sectra uses. Having worked with Agfa and a couple of other systems, including one with the click-and-drag measuring method, I personally prefer the one Sectra uses; less user input necessary. Zooming is, by the way, actually possible in Sectra PACS, while you struggle with your aiming for an accurate measurement. I agree it is really very useful.