The Digital Image by Ashanti Belfon

The difference between Analog and Digital Images.

00076527_1 — 2024-09-21 01:30:09 UTC

~ I found this difference very interesting, and the comparisons to clocks made it effortlessly understandable.

Analog images capture signals as smooth, continuous data, similar to a watch with hands that can show any time.
Digital images are limited to a finite number of values, like a digital watch that can only show specific times. They break the signal into small, individual units (pixels) and store them as numbers, making it easier to process, analyze, and manipulate the image with computers. (Hutchison, 2024)

How does this apply to Radiography?

00076527_1 — 2024-09-21 01:59:12 UTC

Radiographic images are typically analog in nature. This means they capture a continuous range of information, like the shades of gray in an X-ray.
However, modern medical imaging systems often convert these analog images into digital format for processing, storage, and transmission. (Hutchison, 2024)

Pixel size, Matrix size and Field of view.

00076527_1 — 2024-09-21 02:34:42 UTC

~ This portion was fascinating and easy for me to digest.

Pixels are the smallest units that make up a digital image. They are like tiny dots that form a grid or pattern. The more pixels an image has, the more detailed it is.
A matrix is a grid or array of pixels. It defines the size and resolution of an image. A larger matrix means more pixels, leading to a higher image quality.
FOV (Field of View) is the area of the patient's anatomy that is captured in an image. (Abdulla, 2021)

Pixel size and Image Quality

00076527_1 — 2024-09-21 11:18:47 UTC

~ I was a bit confused as to why smaller pixels would improve details.

From research, I found that if a pixel is too large, many details would be "stuffed" into the single pixel. This then appears "stretched" or distorted. While with smaller pixels, details do not have to be shared and can be demonstrated with higher quality.
Additionally, as seen in the image above, when objects are located in the same pixels or ones close by, they merge/blend together since there is no pixel gap between the objects for them to be interpreted individually. (Princeton Intruments, 2022)

How they're all connected.

00076527_1 — 2024-09-21 12:04:36 UTC

~ Understanding the relationship between Pixel size, Matrix size and FOV seemed very important.

FOV and Pixels: A change in FOV directly affects pixel size.
Matrix and Pixels: A change in matrix size directly affects pixel size.
FOV and Matrix: A change in FOV can indirectly influence matrix size, but the relationship is less direct.

Spatial VS Contrast resolution

00076527_1 — 2024-09-21 15:03:29 UTC

~ Knowing the difference between the two is essential and so I created a table for comparison.

Conclusion

00076527_1 — 2024-09-21 15:15:10 UTC

~ In summary, the reading emphasised the key components of digital images in medical imaging, which are crucial as they directly influence image quality, resolution, and thus the ability to accurately diagnose and treat patients.

References

00076527_1 — 2024-09-21 15:16:03 UTC

Abdulla, S. (2021, October 10). Digital radiography - Radiology Cafe. Radiology Cafe. https://www.radiologycafe.com/frcr-physics-notes/x-ray-imaging/digital-radiography/#:~:text=A%20look%2Dup%2Dtable%20(,displayed%20contrast%20of%20the%20image.
Hutchison, C. (2024). Analog X-Ray vs. Automated Digital X-Ray: What’s the Difference? https://www.mavenimaging.com/blog/analog-x-ray-vs-automated-digital-x-ray-what-is-the-difference#:~:text=Conventional%20radiography%20is%20another%20term,manipulation%20and%20enhancing%20diagnostic%20capabilities.
Princeton Instruments. (2022, February 7). Pixel Size and Camera resolution. Teledyne Princeton Instruments. https://www.princetoninstruments.com/learn/camera-fundamentals/pixel-size-and-camera-resolution#:~:text=If%20the%20distance%20between%20the,as%20shown%20in%20Figure%202.