“Dr. Mike’s” analysis of the sphere x-ray

“Dr. Mike” is a physician specializing in Diagnostic Radiology. Without knowing the entire story of the Betz Sphere, we had him take a look at our images and give his opinion about the radiological characteristics of the image, as well as explaining how X-rays work on various material and what we might be looking at. Keep in mind, his specialty is with diagnosing human bone and tissue and not metallurgical X-rays, but we found his insights interesting. All images on this page are Copyright 2019 Astonishing Legends, LLC, All Rights Reserved. Please do not copy or distribute without permission.

“Dr. Mike’s” Comments:

1. The basic process of radiographic image production: A source emits an x-ray photon. When that x-ray hits film, it exposes it, turning it black. Areas not hit by x-rays remain white.

2. Your print is an inverse, like a print of a negative, so the opposite is the case. In other words, most of the photons have hit the film in the white areas, less in the black.

3. An x-ray photon has energy measured in kV. Normal diagnostic x-ray energy is 20-120 kV. For your print – or in the case of your print, they used 300 kV to penetrate the steel nickel.

4. Whether an x-ray photon gets blocked by an object depends on these factors: the object's density (metals are densest, noble gases less dense), its atomic number (higher means more electrons to interact with the x-ray), the thickness of the object parallel to the x-ray path (a long rod oriented in the direction of the x-ray beam has a higher chance of absorbing or scattering the x-ray) and the energy of the x-ray.

5. Because of the steel/nickel shell, most of the lower energy x-rays will be removed before passing into the interior of the sphere, a process called "beam hardening." Only higher energy photons will remain. The higher energy photons have a greater chance of passing through a material without being absorbed. This means that thinner, less dense, lower atomic number objects are less likely to be detected inside the metal container.

6. And so, because the small spheres inside are optically denser than the surrounding, Dr. Harder assumed that they had a much higher anatomic number than iron and nickel, which make up the shell.

7. However, You can see blood vessels inside of the lung on chest x-rays (radiographs), and they appear optically denser than the ribs, especially the ribs on the far side of the detector/film. So what is essentially water (pulmonary vessels) shows up optically denser than calcium (bone). I'm not sure of the physics behind this, but I think this is because the pulmonary blood vessels are surrounded by air and the high contrast between air in the lungs and the adjacent blood vessels makes them visible. You can't see the blood vessels surrounded by other tissues in the chest wall or mediastinum. In other words, the small spheres inside are visible because they are surrounded by air, and can be made of any material that does a decent job of stopping some of the x-rays (probably not wood or plastic).

8. There is only one view of the object. In radiology, we say that "one view is no view." This is because you are taking a 3D object and displaying it on a 2D surface. The spots inside the object may be flat, spheres, or long rods parallel to the x-ray beam. Their location is also not clear. They can be anywhere from the x-ray source housing, surface of the object, interior of the object, far surface, x-ray intensifier screen, x-ray film. The copying process could create them.

9. Objects closer to the film will have sharper margins. Think of your hand making a shadow puppet. As it gets closer to the wall, the edges are sharper. The small lesions inside the object are sharper (especially the round ones), suggesting they are closer to the film.

10. The margins of the sphere are not sharp. Usually, a metal object will have a very abrupt margin with the air. Instead, we see a wide donut of fuzzy gray. I think this is because the x-ray source was placed very close to the object and diffused the shadow, like in the hand puppet example.

11. The three focal "lesions" projected in the center of the sphere. As a guess, I think these are likely surrounded by air inside the object or an artifact on the film or created while developing the film. They have some characteristics of a liquid. The smaller round lesion has a short tail, like a drop that has moved a short distance. The larger angular lesion has smaller round, "droplet-like," densities next two it like you would see in a splatter. Maybe these are two drops that were hanging on the inside surface like a stalagmite, that cooled down, and a third one had dropped to the other side of the sphere making a splatter. I think they may be made of the same or similar material as the sphere shell. If they are on an opposite inner sphere, this might explain why the smaller dots (closer to the film) have a sharper margin than the angular lesion.

12. There are a lot of artifacts on the print. You can't see one side of the sphere, there are "wrinkle" artifacts, and there is quite a bit of noise.

13. There is a thin black line heading down from the largest, angulated lesion, in the 5 o'clock position. Is this a thin metal seam, artifact or?

[A dried, liquid residue pattern in the bottom of a glass] got me to thinking that the larger "lesion" may represent a liquid splatter.

Scott had followup questions for Dr. Mike:

SCOTT: "I have questions about point number 10 on his document. If this is a 300 kV X-ray, wouldn’t that explain the margins of the sphere not being visible? Because the 150 kV wouldn’t penetrate? … also is there any way to calculate density based on the idea that at 300 kV the metal of the sphere is invisible so whatever is creating the 3 spherules inside must be denser?"

We then sent Dr. Mike “Negative” and contrast-enhanced versions of the of the original X-ray image. Here is his reply:

Halos: Regarding the curvilinear density at the margin of the sphere, at 7 o'clock with the nearby blotchy density. The blotchy density is an artifact, similar to ones in the left upper side of the image-see roller artifact image. This may be due to something on rollers as the film is fed through the developing machine. They are artifacts b/c they are outside the sphere. The halo itself, I don't know what it is. Sometimes if the film is bent before being developed with a thumb, you can get a crease like that. It is different than the paper wrinkle artifacts in the upper right quadrant. It could be something else.

I don't see halos around the small round lesions. You can have a visual phenomenon called a Mach Band which is how your brain accentuates the deferences in luminosity at the margins of an object, which would create a darker area immediately next to a lighter object. I don't know if that is what they are seeing.

I think you are right in part about the 300 kV making the margins not visible. I was trying to explain why there is a target appearance (see target image) to the large sphere and thought maybe it was because the shadow of the rim was blurred because the source is so close. If you see an eggshell calcification in radiology, it appears as a thin white line at the margin of a round, gray circle, because fewer x-rays penetrate the sides of a sphere. We don't see that line here, but maybe it is blurred. I think maybe the more interesting point here is that for some reason there is slightly increased density in the center that isn't explained well by the metal shell (marked in green). Does this mean there is more homogeneous material inside? I don't know if refraction could give you this appearance?

The metal shell of the sphere is visible; it is the entire gray circle

There is no way to calculate the density of the inner spheres based on the optical density in the image. The optical density (what you see as darker) is a function of the sensitivity of the film, the thickness and type of x-ray intensifier screen used, the number of x-rays hitting the film cassette. The number of x-rays hitting the film cassette is determined by the density of the object, the atomic number of the object and the thickness of the object. We can't even compare it to the density of the shell because it is in a different environment. You can't say it is denser than the shell because it is surrounded by air or gel. See the x-ray image comparing a water density smaller vessel in the yellow circle which is denser (whiter) than the density of two overlapping calcified ribs in the pink circle. I suspect it is about the same density as the shell. It's not wood, not plastic. It could be denser than the shell, but can't tell.