The Evolution of Radiography: from Analog to Digital Systems

For the better part of the 20th century, film or screen radiology was the prevailing method to produce x-ray images. This analog system was able to provide physicians with a hard-copy image, which they could hold up against light to view and diagnose x-ray images. With the advent of digital systems, patient images would become available almost instantaneously anywhere in the care facility or around the globe.

Computed radiography (CR) and digital radiography (DR) are not always perfect. This paper hopes to explain how analog systems came to be and how their modern counterparts have emerged as the future of radiography.

In the early days of radiology, glass photographic plates were used to produce images. World War I ensured that glass imported from Belgium came to a halt, creating a glass shortage in the United States. The government hired George Eastman, founder of Eastman Kodak Company, to produce photographic film to replace the antiquated glass plates.

The early benefit, naturally, was that physicians were able to view a hard copy of an x-ray image against the light. This allowed them to properly diagnose an image and present the processed x-ray film to the patient for evaluation.

Analog systems are now a rarity. The advent of computers, high-definition monitors, and networks has allowed CR and DR to supplant their analog brethren. As practices switched from analog to digital, they met some obstacles. According to a 2006 study published in the British Business Journal, the initial cost of the systems was an early deterrent for many practices making the switch. Expensive monitors with network connections and software capabilities were required to view the radiographic images.

The new technology also required new skills. The BMJ article noted that physicians and technologists had to adapt to viewing images on a screen. There’s also the case of overexposure. In an analog system, the image would turn dark if the patient was overexposed. DR systems can automatically change the image, showing a well-taken image even if the patient is overexposed.

Even with those disadvantages that the digital era has brought to radiology, many studies show the advantages that digital systems pose. According to a 2000 article by Katherine Andriole published in the Journal of Digital Imaging, patient throughput is one of the industry's biggest selling points. Patient throughput in their study noted that offices using analog systems saw 8.2 patients per day, while when CR is used, 9.2 patients walk across. An average of 10.7 patients are taken care of in offices using the DR system. The BMJ article adds that several US hospitals saw as much as an 82% increase in patient throughput.

One main reason patient throughput is affected so much is because of the time it takes for an image to be processed. According to Andriole, analog systems average about 29.2 minutes for an image to become available for viewing. CR systems have an image availability of 6.7 minutes, compared to 5.7 minutes for DR systems. The improved time in image availability goes up by 80% when discussing DR for film or screen.

In May 2000, Doreen Dackiewicz noted that 67% of patients had a better office visit when using a digital system. The fact that they didn’t have to wait at the doctor’s office so long is the biggest reason for their satisfaction.

The cost of buying digital equipment scares off some physicians. Andriole notes the price difference between CR and DR systems. She concludes that CR systems come out to $95,000, while DR systems run $395,000—a $300,000 difference per room. However, Andriole considers her patient throughput. For CR systems, if you take the 9.2 patients per hour, multiply by 8 hours per work day, and multiple that by 250 work days per year at $200 per exam, the office stands to make $3.68 million per year. For the 10.7 patients per hour if you were using DR, the office would make $4.28 million per year. That’s a difference of around $600,000 between the two systems. Considering the DR system was valued at $300,000 more than the CR system, the DR system is more cost-effective if you have a higher patient volume.

Andriole also noted that what technologists say matters. In a survey of 15 experienced technologists, she wrote in the Journal of Digital Imaging that all participating technologists unanimously favored the DR systems as "much better" than the analog systems and higher than CR.

Film and screen analog systems served their purposes after World War I.Technology has made it more convenient for digital systems to replace antiquated analog systems. Physicians can access images instantaneously from around the world. CR systems were a great way to bridge the gap between the analog and DR systems. But as novel an idea as DR systems are now, it’s only a matter of time before they too become obsolete.

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