Two of my roles are rather heavy on acronyms: being a space engineer and a cancer patient. NASA (itself an acronym, of course) is renowned for being fond of TLAs (three-letter acronyms). Sometimes this makes sense, as it can shorten long, tech­nical terms to manage­able length. However, some­times it actually has the opposite effect; for example, the acronym for the two-syllable word "pilot" is the three-syllable PLT.

In the cancer area, terms can again be quite con­voluted, so acronyms can help to simplify things. For instance, many of the treat­ments for multiple myeloma are made up of combinations of several separate drugs, and it is much simpler to refer to, for instance, VRD than to Velcade-Revlimid-dexamethasone.

In both fields, people sometimes forget, or do not all agree on, what any given acronym actually stands for. In the cancer field, CR is sometimes thought of as com­plete response, and sometimes as com­plete re­mission. Complete re­mission sounds better, with its connotation of being virtually a “cure,” but com­plete response (to a treatment) is presumably more accurate.

Similarly, in the space arena, an example of ambiguity is the RPM “back-flip” that later Space Shuttle flights performed when approaching the International Space Station. The RPM allowed the station astronauts to inspect the underside of the Shuttle for damage to the tiles. This maneuver is sometimes said to be short for rendezvous pitch maneuver, and sometimes R-bar pitch maneuver; nobody seems to be sure.

The reason I started thinking about acronyms lately is that I have just had a positron emission tomography (PET) scan. It wasn’t scheduled because I am having any problems that we had to delve into; my health seems to be very stable right now, with good blood test results (IgA and kappa light chains). My Revlimid-dexa­meth­a­sone treat­ment dosage has even been cut back a bit over the past year or so as a result. Rather, the scan was because my oncologist would prefer that I have an X-ray “skeletal survey” every year, but I have been digging in my heels, as they never seem to raise anything in my case apart from false alarms.

For instance, the last time I had one some years ago, it appeared to show myeloma coming back in a lower vertebra. However, a follow-up magnetic resonance imaging (MRI) scan showed that this was just arthritis. (After worrying mightily while waiting for the results of this MRI, I remember phoning my wife to excitedly announce “I have arthritis!”.) So, since my doctor really wanted me to have some sort of scan this year, and I wasn’t a big fan of X-rays, we “compromised” on a PET scan.

As an engineer, it might be assumed that I would have studied in detail all the various tests that we go through. However, I hadn’t researched PET scans until recently. It therefore only then occurred to me that the P in PET stands for positron, or the anti-matter equivalent of the electron. This is pretty futuristic stuff! I tend to think of anti-matter as something that, since it is destroyed so readily by “regular” matter, can only occur in very exotic environments like neutron stars. Instead, it turns out that it is the basis for this type of somewhat common medical test.

In a PET scan, the patient is injected with a radioactive glucose analog that has a very short half-life. The analog is taken up by parts of the body with signif­i­cant metabolic activity (for instance, cancer sites) and produces positrons that annihilate with electrons, causing gamma rays to be emitted. These are then used, in a sophisticated computerized imaging (tomography) system, to produce images of the activity. After my scan, the technician recommended that I not visit any federal facilities that afternoon, as I would be mildly radioactive and so might set off a Geiger counter! We don’t actually have Geiger counters at the entrance to NASA, but it seemed like a good excuse to take the afternoon off work.

I was quite excited at the idea of using all these exotic objects (radioactivity, positrons, gamma rays) to produce such useful images. How­ever, the acronym PET is perhaps a shade heart-warming for something that involves matter-antimatter annihilation.

In similar fashion, there are stories that, many years ago, the military was interested in flying a space station to carry out reconnaissance. They considered calling it the manned orbital module, as no congressional budget committee could ever say no to MOM. Despite this plan, though, it somehow never materialized.

A contrasting case is MRI: the original name for this type of imaging was nuclear magnetic resonance (NMR), even though it uses no radioactivity. Rather, the “nuclear” in the name referred to the nuclei of atoms in the body that are set resonating by the applied magnetic fields. It was eventually decided that this name gave people the wrong impression, so it was changed to the less alarming magnetic resonance imaging.

I had expected that my PET scan would show pockets of myeloma in some bones somewhere, and won­dered how that would make me feel about those areas of my body. Instead, though, it didn’t appear to show any signs of myeloma at all.

Of course, being such a sensitive test, it did end up finding something else to investigate, but it is unrelated to myeloma. There’s always something to deal with when it comes to the aging human body.