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  • Michael Francis Ayapana

Film, Computed Radiography (CR), or Direct Digital Radiography (DR)? Which modality is the best?

Updated: Apr 21, 2021

Have you ever been to a radiology clinic for your X-ray? If yes, then you’re certainly aware of X-ray films. Generally, X-ray films are used to capture the medical imaging of your skeletal structure.

Now, radiography is shifting from film to digital radiography. Computed Radiography (CR) and Direct Digital Radiography (DR) are the two available choices for Digital Radiography systems.

Let’s talk about each one of them to find which modality is the best.

Chest X-ray Film Image
Chest X-ray Film Image

Film Radiography

Like several film mediums, radiography also started its journey in the same way as photography and videography. The screen films were used to show imagery before photography and videography moved to digital. In order to produce a film radiograph, radiologic technologists will place an X-ray film inside a cassette containing intensifying screens. After exposure to an X-ray beam, the cassette will be brought inside a dark room for processing. Processing could be manual or automatic. Manual processing uses a developing tank while automatic film processors are used for automatic processing. After developing the image, the wet film will have to be dried. Due to this complicated and inefficient procedure radiography is gradually shifting away and moving towards digital.

Most practitioners and medical imaging centers are still using film radiography because it’s serving them. For clinics and radiology centers, film radiography is still functional, and they’re not yet willing to make a shift. However, they have to shift away when the demand for digital radiography increases, and people start to prefer it.

Eventually, digital radiography will be much more efficient and cost-effective – in fact, it still is. The cost-effectiveness of digital radiography comes in the form of saving cost on films and solutions purchase. Films, solutions and other dark room equipment are required to produce radiographs. However, digital radiography doesn’t require these, and you save a huge amount of money especially in the long run.

Computed Radiography (CR)

FireCR Computed Radiography System
FireCR Computed Radiography System

When it comes to using a digital system for radiography, medical facilities have two choices in the form of Computed Radiography (CR) & Direct Digital Radiography (DR). The major difference between conventional X-ray is that Computed Radiography (CR) replaces the film and intensifying screen with Computed Radiography (CR) cassettes containing photo-stimulated luminescence screens.

A Computed Radiography (CR) system works on digital image acquisition and processing principles. Computed Radiography (CR) cassettes are exposed to X-ray beam the same way as regular X-ray film. The cassette will then be inserted in a Computed Radiography (CR) reader wherein advanced laser and optical technology scans the stored X-ray radiation. This will result to emission of light from the phosphor screen that will be fed into a photo-multiplier. The next step would be conversion of the received signal from analog to digital. The resulting digital image can then be processed, displayed, archived, and exported by using the CR workstation.

Computed Radiography (CR) provides key benefits over film radiography. Computed Radiography (CR) system lets the radiologic technologist do post processing on the acquired digital image. This includes zooming, cropping, adjusting of brightness & contrast and even placing annotations and markers. You can print the digital images on film printers, or send them to the radiologist by using a teleradiology system.

Clinics shifting from film radiography to digital may consider Computed Radiography (CR). The cost of setting up a Computed Radiography (CR) system is much less than a Direct Digital Radiography (DR) system. Another advantage is that multiple cassettes can be used on one CR scanner, meaning, simultaneous X-ray scans can be performed. This could be done in a DR system but the cost will be much higher because you will need to purchase another flat panel detector (FPD) to achieve the same volume of patient.

With some upsides, it comes with some downsides as well. The PSPs used in Computed Radiography (CR) systems have a limited lifespan. Some manufacturers can only guarantee good quality images for up to 30,000 to 60,000 scans. Computed Radiography (CR) systems being highly mechanical is another key issue that needs to be addressed because the gears, belts, stage, laser steering, fiber and eraser assemblies can be susceptible to wear and tear.

Direct Digital Radiography (DR)

Vieworks Digital Radiography System
Vieworks Digital Radiography System

Direct Digital Radiography (DR) is the latest technology and the best of all. A Digital Radiography (DR) system is the epitome of digital radiography. It uses a flat panel detector (FPD) to pick up the X-ray radiation and a workstation to process the image. The entire process of converting the X-ray radiation into a digital image would only take around 5 to 10 seconds – A big advantage over film and computed radiography (CR).

Direct Digital Radiography (DR) produces better quality and sharper images than Computed Radiography (CR) and film as well. This lets you scan more patients in less time. If the workload is huge, like when doing annual medical examinations (AME) for a company, then Direct Digital Radiography (DR) is an ideal choice because it enables you to cater up to 100 patients an hour. The patients need to spend less time waiting for their turn, which improves the overall experience.

Direct Digital Radiography (DR) makes a substantial difference with less radiation exposure. According to DQE (Detective Quantum Efficiency), the X-ray detection efficiency of Digital Radiography (DR) systems is about 65%, whereas Computed Radiography (CR) systems have only 30%. DQE measures the efficiency of x-ray detection of a radiography system.

Direct Digital Radiography (DR) holds the best image acquisition & processing capabilities among the three radiography systems. It takes less than a minute between exposure to radiation and image acquisition. Digital Radiography (DR) systems are portable, and some of the systems have wireless DR detectors. Reliability of DR is also the best. Some brands offer shock proof, water proof and dust proof models.

One major issue with the older version of Direct Digital Radiography (DR) is the use of CCD technology. CCD (Charged Coupled Device), unlike FPD (Flat Panel Detectors) has a bigger form factor and heavier weight. It also produces lower quality images than FPD DRs. Another downside is cost-related. You need to make heavy investments to set up a Direct Digital Radiography (DR) system in your medical facility. The upfront cost is huge, which makes Direct Digital Radiography (DR) systems a “not-so-ideal” investment for medical facilities with fewer patients.

Which modality is the best?

There’s no right or wrong answer in this case. The ultimate deciding factor comes down to your needs and budget. Technically speaking, there’s no doubt that Digital Radiography (DR) is the epitome of high-quality radiography.

If you’re operating a small clinic and only caters a few number of patients, your existing conventional film radiography system is ideal. For imaging clinics, Computed Radiography (CR) is a smart choice because of efficiency and cost-effectiveness.

Digital Radiography (DR) is so far the best modality in the context of efficiency, durability and quality of images. Digital Radiography (DR) systems are the best choice for hospitals with outpatient facilities and also industrial clinics providing pre-employment medical examination (PME) and annual medical examination (AME) services. Given that the patient throughput is huge, quick ROI is guaranteed. Direct Digital Radiography (DR) is much less labor-intensive and efficient than film radiography & Computed Radiography (CR).

Want to see how these different image processing techniques work in radiography? Watch the following videos:

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