Transcription
We've spent some time now looking at the cathode and the anode, which are by far and away the most important structures within the X-ray tube when it comes to our X-ray physics module.
Now, in many exams, especially countries which write short answer question exams, the X-ray tube labeling, the components, and naming the structure and function of those components is a really common question that comes up. So, I just want to spend a moment here labeling the structures that we haven't talked about within the X-ray tube.
So, we know our cathode here. We know our electron beam with our filament on the cathode, our actual focal spots, our anode here. This is our anode stem, and our anode rotates using these stator rotors or stator motors that use electromagnetic induction in order to rotate that anode.
The anode and the cathode lie within a glass envelope. You can see by this blue structure that surrounds the cathode and the anode, this is a glass envelope which has a vacuum inside. There is no air within this glass envelope, and that allows our electrons to pass towards our anode unobstructed. We don't want those electrons to interact with any other atoms or molecules prior to striking the anode. We want all of that energy to be deposited into our actual focal spots on the anode.
Now, X-rays are produced at this actual focal spot, and they will exit the X-ray tube through an X-ray window here. This X-ray window is generally made up of aluminum or beryllium, and it filters out some of the lower energy X-rays that are going to contribute to our patient dose but not to our image.
X-ray production is what is known as isotropic. When we produce an X-ray within the anode, those X-rays can spread out in 360 degrees. There's no organized manner in which those X-rays are released from the anode. So, X-rays can go in 360 degrees in all directions, and this window only allows this specific part of that isotropic X-ray release to be released towards our patient.
The rest of the tube housing is made up of a highly attenuating material, which is normally lead, that prevents any X-rays from spreading out away from our patients, exposing staff or other patients that aren't getting the X-ray. We don't want those X-rays to reach anyone else. We only want this very specific beam of X-rays to head out towards our patient.
Then we can see that there is this conducting oil that surrounds this glass envelope. The conducting oil moves around within the X-ray tube, transferring heat away from our anode and towards our tube housing.
We then have power supply to our X-ray machine that has multiple functions. The first, we run current through our filament and create electrons through the process of thermionic emission. Secondly, we want to provide a tube potential, a voltage difference between our cathode and our anode, that accelerates those electrons towards our anode. We also have a power supply that goes to these stator motors that controls the rotation of the anode, that allows the anode to deal with all that heat buildup. So, those are the major components within the X-ray tube.
Now, we're going to go and look at the X-ray beam geometry, actually look at the X-rays that exit the machine and how changing our anode angle will affect that X-ray beam geometry. After that, we'll head and look at our X-ray circuits and see how we go about actually powering this X-ray tube, and then we will move on looking at the bremsstrahlung and characteristic X-ray production at the anode. So, I'll see you all in the next talk. Goodbye everybody.