MRI is by far the most important diagnostic tool for brain tumors, and for good reason. If you're even suspected of having a brain tumor, chances are good that you'll get at least one brain MRI. After diagnosis, MRI can be used to evaluate treatment efficacy. After treatment, MRI aids in surveillance, watching for progression, recurrence, or further complication of the original condition.
In retrospect, the fact that I would end up undergoing multiple brain MRIs should have come as no surprise. My ultimately successful attempt to find a cause for a funhouse of symptoms led my doctors to schedule a brain MRI. My later attempt to expedite it landed me in the ER. This quickly led to brain surgery. At every step, brain MRI was there. To date, I count six MRIs that have been performed on my brain. Five took place in 2023, after the appearance of symptoms that brought me into the ER. A sixth brain MRI took place several years earlier for an unrelated condition.
If I had to condense the experience of getting a brain MRI into a single emotion, it would be fear. I've experienced two kinds. The first comes from imagining what happens after the procedure. Brain MRIs don't get ordered at the drop of a hat. They're expensive, and there's enormous demand for imaging time. Every MRI procedure therefore carries a much higher than zero probability of scary stuff creeping out the other end. The second kind of fear stems from what happens during the procedure. I can't do much here to allay the fear that comes from not knowing what happens after the MRI, but I can do something to allay fears due to not knowing what happens during one.
Preparation for my brain MRIs has tended to start several days before the actual scan. The staff typically forward a set of "Visit Instructions." All of them relate to the high magnetic field strength, typically 1 Tesla or more, I'll soon be exposed to. According to Popular Mechanics, that's roughly equivalent to 200,000 refridgerator magnets worth! Metal accessories such as jewelry, magnetic clip-on eyelashes (really?), rings, and piercings, are not to be worn. This was easy to understand. During my time as a synthetic organic chemist I'd performed hundreds of nuclear magnetic resonance (NMR) studies. And I'd heard the stories about metal object left too close to an activated magnet. Leaving my wallet (due to magnetic stripes), and metal objects such as keys well out of range of the magnetic field was standard practice. The MRI facility I went to had a long list of questions, mainly relating to jewelry and implants, that needed to be answered before a scan would start.
More surprising were the restrictions around clothing and skin treatments. It turns out that some consumer-grade fabrics heat up in the presence of strong magnetic fields. The effect is large enough to cause serious skin burns. For this reason, I've always been told that I won't be wearing any of my own clothes. The only "clothing" I've been allowed to wear is a hospital-issue gown and anti-slip socks. To this day I haven't figured out how to properly close the gown. Fortunately, I've long since stopped caring. Similarly, some makeups and skin lotions can also heat up in magnetic fields, which would be a serious problem. As a result, I've been discouraged from applying anything to the skin before a scan. It turns out that even some kinds of tattoos can heat up under the strong magnetic fields in an MRI.
All of my brain MRIs have used a "contrast agent," typically Gadobuterol (Gadovist). Gadovist is administered intravenously, which adds a layer of anxiety and/or discomfort not present in contrast-free MRIs. During my first MRI many years ago, contrast was injected by popping me out of the unit mid-procedure, injecting, then popping me back in. More recently, I've been routinely fitted with an IV port. This port is then connected to the MRI unit, which injected contrast agent as needed. As the inside of my right arm accumulated needle damage due to repeated injections, ports, and blood draws, it became ever more difficult to insert the needle for the contrast agent port. As a result, one time the needle was inserted into my hand. I've always been fitted with the IV port before entering the room housing the MRI unit itself. This procedure can take anywhere from a minute or less to ten minutes.
The purpose of contrast agent is to detect leaks in the blood-brain barrier (BBB). This barrier protects the brain from a wide range of potentially harmful materials carried by the blood, including bacteria, viruses, proteins, and a wide range of small molecules. It also turns out that the human BBB is in its healthy state impervious to Gadovist.
Gadovist contains gadolinium, a rare earth element. Like certain forms of iron and indeed other rare rare earth elements, gadolinium exhibits paramagnetism. This paramagnetism means that tissue exposed to Gadovist has a brighter (higher) MRI signal than it would otherwise. This is the origin of the contrast effect.
It's this combination of properties, inability to cross the BBB and signal enhancement, that allows Gadovist to serve as a kind of BBB leak detector. Gadovist will be mostly absent in healthy brain tissue because the BBB prevents entry. But in brain tissue that's been damaged through a lesion of some kind, Gadovist can enter, resulting in a characteristic brightening or ("enhancement"). In other words, healthy tissue tends to look the same in MRI regardless of whether contrast has been administered. Damaged brain tissue, on the other hand, tends to become brighter after the injection of contrast.
In addition to this leak-detection mode, Gadavist can also pinpoint the location of tissues having abnormally high concentrations of blood vessels ("vascularization"). This is a hallmark of glioblastomas, for example.
In my more recent brain MRIs, contrast agent was administered during image acquisition itself. During injection, the sensation was cold, as if alcohol had spilled on the skin. In fact, this was my first thought as the MRI unit injected contrast agent during one session. I expected to find a mess of contrast agent and possibly blood due to the needle having slipped out. Instead, it was merely the low temperature of what was injected. Sometimes, the injection of Gadovist resulted in the vague taste of metal.
Inside the Tube
I'm not claustrophobic by any stretch, but do freely admit to feeling uncomfortable at times in an MRI unit. Imagine being inserted into an eight-foot long tube whose diameter is roughly 1.5 times the width of your body, head first. The boundary of your enclosure might be as close as a few inches beyond your nose. Then imagine being left in that state for up to 45 minutes. Also imagine being told that the slightest movement on your part could prolong the ordeal even further.
The barrage of loud, electronic sounds, often reminiscent of EDM, is not unique to brain MRIs. I've always been offered ear plugs, which I gladly accept. I did find it odd that one of my brain MRIs used a sequence that sounded suspiciously similar to the synthesizer intro in Peter Schilling's Major Tom.
What I found unique to brain MRIs is the extent to which my head was forcibly immobilized and encased. Prior to being inserted into the tube, I was asked to lie face-up on the unit's sliding table, while placing my head into a concave headrest. Below the headrest were two shoulder rests. I was then asked to slide myself up until my head touched the top of the headrest and my shoulders made contact with the shoulder rest. On either side of my head were vertical plates. Between each plate and the ear closest to it was inserted a foam cushion (over the earplugs).
In this way, my head was isolated from motion in all directions, except possibly up-down. However, that motion was highly unlikely due to my body position.
Next, a grill-like "coil" was lowered into place over my head. The bars of the grid couldn't have been more than a few of inches from my nose. The coil plays an integral part in signal detection for brain MRIs. As far as I know, it's not optional.
This additional gear has the effect of increasing the discomfort and/or anxiety of being unable to move, touch my face to scratch an itch or tickle, change position, or extract myself directly from the unit. I try to make sure that my final state is one I can maintain for 45 minutes. On one occasion, this didn't work because my head was jammed too tightly into the headrest. I decided to stick it out anyway because there was no way I was going to prolong the procedure any longer than necessary.
Prior to being inserted into the tube, I've been given a squeeze bulb, typically placed into my left hand. I've never had a good look at it, but it seems to be similar to the squeeze bulb used in blood pressure meters. I'm always told that if I feel the need to come out for any reason, I can squeeze the bulb. So far, I haven't had to do so.
I've been offered a choice of music during only one brain MRI. It's far from clear how this would work. It's so incredibly loud inside the tube that any music played must be blaring at uncomfortable levels. Regardless, I declined the offer. Fortunately, EDM is Ok with me.
Just prior to this year's round of brain MRIs, a link on Mastodon (related to my favorite programming language of all things) coincidentally guided me toward the audiobook version of Practical Zen by Julian Daizan Skinner. I found the breathing technique described there especially useful for dealing with the discomfort caused by the long times, closely confined space, sometimes jarring noises, and acute immobility required by brain MRIs. From what I gather, deliberate breathing through the belly, and counted breathing in particular, is a basic skill taught in many mediation courses. Either way, I've found it very useful, especially when combined with keeping my eyes closed.
There's no way to sugar coat it: getting a brain MRI is no fun at all. Fortunately, repetition, experience, and some simple techniques have alleviated the worst aspects of it for me. Even so, I have experienced one variant of brain MRI that's worse by a mile. The next article will describe it in detail.