Thursday, October 5, 2017

Gadolinium Poisoning From MRIs - Why My Case Was Different

The WSJ article 'A Question For Anyone Getting An MRI' (Sept. 19, p A11) performed a public service by alerting readers to the dangers of gadolinium poisonings from MRIs.    This danger applies to any magnetic resonance imaging performed with a gadolinium-based contrast agent - called a GBCA.  As the article notes:

"This leaves metal deposits in the body's organs and tissues including the brain."

We are then informed that researchers are "exploring whether the agent harms patients"

But already we learn. (ibid.):

"Some patients with healthy kidneys are reporting getting sick from the dye and are pressing for more research and warnings to the public. Doctors for years cautioned patients with serious kidney problems about getting MRIs that use Gadolinium because their kidneys can't always fully flush out the metal toxins."

Indeed, earlier in September, an FDA Advisory Board voted 13 to 1 in favor of adding a warning on labels, that gadolinium can be retained in organs, including the brain and kidneys.   We also learned that certain types of agents - called linear GBCAs - have a greater retention than others such as macrocyclic GBCAs.   Given this,  there is definitely a  need to regulate such MRI contrast dye use- including restrictions for pregnant women and children.

More details (ibid.):

"Gadolinium is a metal dye injected into the veins to help radiologists better read an MRI scan. The dye is used, experts estimate, in as many as half the millions of MRIs performed annually in the U.S. - generally for scans that are looking for tumors, severe inflammation or blood vessels. Doctors say the dye makes it possible to detect and diagnose more detail.  MRIs looking at bone and joint issues don't need a contrast agent for doctors to make a diagnosis."

Neither, evidently, do MRIs for detecting prostate cancer, such as the MRI I received back in June last year.

As I noted then,  MRI technology has proceeded so markedly in the last ten years (due to what is called faster development of "echoplanar surfaces" - or MRI image slices) that the latest machines can now actually find and grade carcinomas that occur there.  The key has been the development of  more powerful 1.5- and 3-Tesla scanners where Tesla refers to the magnetic field strength. (1 T = 10,000 Gauss). The machine that scanned my pelvic region was 3T or fifteen times greater than the magnetic field of the most powerful sunspots. This strength of magnetic field required no "dye" or contrast to detect tumors in the gland.

The key basis then was a quantum leap in signal to noise ratio (or "SNR") with the SNR increasing with magnetic field strength. Thus, the 3T (and 1.5T) machines  are ideally suited to the task of scanning for prostate lesions in the pelvic area.

According to one radiology website:

"Current receiver coil technology includes pelvic phased-array coils with or without the addition of an endorectal coil. The endorectal coil adds approximately an order of magnitude to the available SNR  and also allows for the use of small fields-of-view (FOV) for some critical applications"

In other words, the radiologists conducting the exam seek ever greater enhancement of SNR by use or coils (pelvic phased and endorectal) by using ancillary devices that play the same role as a radio receiver or antenna. The pelvic array coil - which was used on me  was somewhat like one of those protective pads dentists put on you when taking dental x-rays except these are filled with coils to  receive radio frequency inputs from the MRI.  In the MRI case it is fitted snugly around your waist before you go into the machine.

The endorectal coil is actually a thin wire inserted inside a balloon filled with 50 ml of air to fix the coil to the prostate for better reception of the radio frequency waves and superior SNR. However, much of the literature so far disputes these ERCs improve imaging that much over what an external pelvic coil delivers.

In my case,, only the outer pelvic array coil was used not the ERC.  But this was good enough to detect and give a preliminary diagnosis.

If you're planning on getting an MRI soon it would be well to investigate exactly what kind it will be and especially if a gadolinium contrast dye will be needed.  Also, inquire of your primary doc if you are an at risk candidate for this type of MRI.

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