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Digital radiography is an extension of radiography,

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especially from past 20 years, we've moved from film screen

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radiography to digital radiography.

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The next few slides, I want to talk about the fundamental

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physics principle regarding digital radiography.

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Why did we adopt digital radiography?

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Here is an example showing the advantage of

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digital versus the analog. As you can see here, the

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film screen system has a limited dynamic range.

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It acts the shape of a S curve, whereas

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with a digital system, you have a wide dynamic range,

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which means even with a low radiation exposure to the

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image can be salvaged by adjusting the

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contrast and the brightness on the digital image.

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Like we all do with our photo images we take on our iPhone or

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any cameras, we can adjust the brightness and the

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contrast. That is not possible with the film screen.

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With the earlier days when we used the film screen rolls on the camera,

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what you take the shot is that's it, we can't manipulate.

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With the digital, we can manipulate.

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So further explaining or exploring what the different type

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of digital acquisition is possible, this particular

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slide will tell you an overlay of the picture of the

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comparison between direct versus indirect capture

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within the digital. So

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if you look at the X-ray image capture now done,

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that can be observed either captured by an analog

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system. When you say analog system, that is the film screen

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system,

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and if you also can capture on a digital detector.

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Now, the digital detection can be done in a multiple

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ways, and that also has introduced multiple

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pathways to digital radiography. One of the

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pathways, indirect digital, and that it

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implies computed radiography plate.

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This is almost like the film screen system, which

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means the radiography room, which had a X-rays

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tube and a film screen cassette capability, can be

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quickly converted into digital because the CR plate came out with

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the same size as the film screen cassette.

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So instead of a film screen cassette, you can insert a CR plate and

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the whole acquisition mode will become digital acquisition.

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But the physics principle behind is indirect digital.

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Then there is also called as direct digital.

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This direct digital implies the whole radiography room has to be

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changed, the X-ray tube, and the detector all has to be updated

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to accommodate the digital radiography.

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Under the direct digital, there are two different pathways.

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One is called indirect capture, the other one is direct capture.

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I'm going to walk through these three mechanism, which is very

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important for understanding digital radiography.