I had the opportunity to take a ride in a CT scanner yesterday. It was my first such experience. It’s a great opportunity to pick up a few milliSieverts if you find yourself short in the ionizing radiation department. The particular device I refer to spins a helical beam of x-rays through you as the platform moves you through the big donut with its rotating source and detector.  Through the magic of the integrated circuit and millions of lines of software code the computer reconstructs images based on extinction of the x-ray beam as it careens through your tissues.

During this wierd little Roentgen ride I had a peculiar experience. After the iodinated tracer injection the radiologista trots around the shielded wall, clicks “go” and the sequence takes off. As the beam was scanning from head to chest I had the distinct sensation of a horizontal thin blue line in my visual field for just a beat. Because my eyelids were closed I was not seeing a focused image through the lenses of my eyes. Against the backdrop of latent images slowly fading from consciousness there appeared the line. I was not thinking about this at the time- I was focused on obeying the breathing instructions.

My theory is that the visual stimulus was the result of the x-ray beam inducing a bit of fluorescence acreoss the width of my retina.  There are plenty of pigment molecules in the retina as well as the tracer compound coursing through the retinal vasculature.

Question- Has anyone else had or heard of such a phenomenon?

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