Hi, everyone:
I asked Dr. Chang about the apparent increase in the AP measurement of my AN over the last 17 months. (The AP -- or antero-posterior --measurement is the second of the three listed in my signature below.) Although it only increased from 12 to 13 mm over the last year (which is not significant, given the 2mm margin of error inherent in MRIs), the measurement was 10 mm seventeen months ago -- an apparent increase of 3 mm since. Was this swelling or regrowth, I wondered?
Neither, it turns out. Dr. Chang took another look at my films. He had measured my AP dimension obliquely (at an angle) in my latest MRI but at a perpendicular vector in the one taken in June, 2009. An apples-to-oranges comparison. When he re-measured my AP dimension on the current films along a perpendicular vector, it measured 11 mm -- only 1 mm greater than the 10 mm measured in June, 2009, and technically insignificant. In plain English, when the measurements were taken at the same angle for both MRIs, and allowing for the margin of error, there was no change.
This reinforces what I and a number of other people on this forum have said before: the dimensions of your AN that your doctor cites are slightly arbitrary. That is, if the measurements are taken obliquely (as they often are), it is totally up to the guy taking the measurement as to what angle they will be taken at across the span of the tumor, easily resulting in a 2mm or higher variance from what someone else might measure using a different angle. (ANs are measured obliquely to include any lobes that jut out from what might otherwise be a symmetrical shape.)
The lesson here is to not take your AN measurements as absolute, exacting gospel. While they are probably the most accurate measurements you're going to get, know that there is some wiggle room. Because of the irregular dimensions many ANs have, we can't expect our doctors to remember what angle they measured across the span of your tumor a year (or two or three) ago. If you are competent in reading your own MRI and feel comfortable making your own measurements, by all means make them yourself and compare your measurements with what your doctor came up with. You'll get a better feel for how your AN's size is changing (if at all). And keep a record of the trend in size over the course of all your MRIs. It was my attention to this trend which led me to question my latest measurements and resulted in my getting a more consistent evaluation -- and greater peace of mind.
Best wishes to all,
TW
