Since X-ray has been used in the medical field, now it spread to all walks of life (casting, automotive, electronics manufacturing, etc.), all aspects of industrial X-ray products, especially imaging components, are slowly spreading from the medical field.
The image intensifier was born in the 1950s and is a great product. His appearance has ended the history of fluorescent screen imaging. We no longer need a lot of high-intensity X-rays to image the screen. It drastically reduced the dose of X-ray fluoroscopy, and the convenience of the doctor’s operation was greatly improved, and patients and doctors were given better protection.
Similarly, with the development of technology, image intensifiers gradually entered the old age, and the replaced fate has long been arranged. With the breakthrough of various dynamic imaging technologies, image intensifier imaging technology has gradually been eliminated.
Today, I don’t want to cherish the image intensifier. I only work with you to analyze why the image intensifier has been eliminated. I think there are several main reasons:
First: the imaging area is small.
Let’s take a look at industrial products. The image on the left is the image of the shadow-increasing test. Only a small part can be seen. On the right is a 17-inch large flat-panel detector. One picture can take a complete product. In theory, the size of the object is smaller than the shadow and the effective area of the flat panel detector. A picture can take a complete product.
Let’s take a look at the medical X-ray machine. As you can see in the picture below, the image on the left is an image of the whole digestive tract. It can only see part of the target position in one image. On the right is the current mainstream large-size flat-panel detector imaging, which can see the entire digestive tract in one image, which makes it easier to observe and diagnose.
The small size of the image area is a very important reason for the limited development of image intensifiers. Then, can we increase the image intensifier size? In fact, from the working principle of the image intensifier, as the imaging area increases, the volume of the entire image intensifier increases greatly, and eventually, it can not be used in the whole machine. Therefore, the largest image intensifier can only reach 12 inches. And normally industrial image intensifier is 2/4inch.
Second, easy to be distorted
Image intensifiers, due to their working principle, they are prone to distortion. There are two main types of distortion: one is circular equalization geometric distortion; the other is asymmetry, commonly referred to as S distortion.
The reason for geometric distortion is, to project an X-ray image onto a surface, an object on the entrance plane produces an image at the edge of the input screen, which is larger than the image produced in the middle. This distortion is related to the geometry of the input screen and the X-ray source position, so it is called geometric distortion. A lens with negative distortion will partially compensate for the positive distortion caused by the curvature of the input screen, thus reducing the overall distortion of the output image, but the distortion phenomenon cannot be avoided.
Another type of distortion is called S-distortion, because of the S-shaped image that is characteristic of linear objects, which is caused by the interference of the stray magnetic field caused by the Earth’s magnetic field or surrounding equipment.
Because of the distortion of the image intensifier (as shown in the figure below), there is a serious interference with the X-ray image inspection results. It is easy to misjudge the defects in the industry, and it is easy to lead to missed diagnosis and misdiagnosis in medical treatment.
Third, low contrast
At present, the dynamic range of mainstream X-ray imaging is 14 or 16 bits, while the image intensifier‘s dynamic range is 10 bits. In other words, the current dynamic range of mainstream dynamic imaging products is 16 or 32 times the image intensifier.
The dynamic range is different, resulting in the same result as shown below. The dynamic range on the left is significantly different from the comparison on the right, so the image’s fineness and color are quite different.
Below is the industrial image intensifier image. The dynamic range of 10 bits, some parts of the product with similar density/thickness, the color will be more similar and no clear outline can be seen. The 16-bit flat-panel detector can distinguish the color in black and white grayscale more carefully. Compared with the 10-bit image intensifier, the gray level is 64 times more, which makes the inner contour of the imaged product clearer and avoids misjudgment.
Below is the image of the medical image intensifier. The dynamic range of 10 bits, in the observation of lesions with small differences in image density, especially in exudative and diffuse imaging pathological changes such as early lung changes in SARS, there is no way to diagnose it, which can lead to missed diagnosis and misdiagnosis.