Radiology in Small Doses: The Benefits of DR versus CR

If science fiction were fact, most modern ailments could be diagnosed and cured by simply waving a hand scanner over the affected body part. The truth is that while we’re not there yet, we’ve already come a long way from the scalpel-intense exploratory surgeries of the past, thanks to the modern X-ray.

Today, X-rays are used to screen for, diagnose, and treat all kinds of medical conditions almost anywhere on the body - from identifying heart disease to destroying cancerous tumors. And as a result of this widespread use, nearly 35% of all radiation exposure in the U.S. now is due to medical X-rays - up from about 11% in the 1980s, according to the National Council on Radiation Protection and Measurements. That’s an increase of almost 500% over three decades.

While the risks are well understood and overwhelmingly outweighed by the benefits, reducing radiation exposure remains a key goal of everyone involved in the X-ray device and health care industry. As a result, technological innovations are giving us a massive dose of relief by maximizing imaging efficiency, while minimizing exposure.

Computer radiology (CR) images have been available for more than two decades in the form of detectors based on photo-stimulated luminescence screen cassettes. The screen cassette converts the X-ray data into digital recordings and has widely replaced the traditional X-ray film cassettes of the past.

So rapid has been the development of digital imaging, that by the early 2000s, a “digital revolution” was taking place with the advent of digital radiography (DR) systems - active matrix flat panels consisting of a detection layer deposited over an active matrix array (AMA) of thin film transistors. These flat panel devices can instantly display a higher image quality than most CR systems, and have notably improved workflow as more images can be taken and processed in the same amount of time.[[{"type":"media","view_mode":"media_crop","fid":"30158","attributes":{"alt":"Richard Colbeth, Varian Medical Systems","class":"media-image media-image-right","id":"media_crop_2872180496555","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"3149","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 153px; width: 160px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"Richard Colbeth, Varian Medical Systems","typeof":"foaf:Image"}}]]

Most significant, however, is that DR has at least twice (2X) the dose efficiency of CR or traditional film. Indeed, studies have shown that DR can be up to three times (3X) more efficient, depending on the type of DR used. To clarify, there are two different types of DR - one based on Gadolinium Oxy Sulfide (GOS) and the other based on Cesium Iodide (CsI). While GOS tends to be less expensive, it is also less dose-efficient. GOS still has, however, a detective quantum efficiency (DQE) of 35%, which is better than the DQE of CR at 25%.

In further comparison, DR with CsI is two to three times more efficient than CR, with a DQE of 70%. This means that clinicians benefit from the same image quality for the dose, while at the same time, the process is more efficient; the speed of film is fast enough to expose quickly and avoid blurring due to patient motion. Ultimately this all results in lower doses to the patient and less exposure risk to the technician.

While we’re not yet at the point of science fiction films with starship captains saving crew by waving flashing devices over lifeless bodies, DR brings physicians and radiology technicians further towards the important goals of improving the speed, accuracy and efficiency of patient diagnosis and treatment. As we increasingly depend on the benefits of X-ray technology, DR helps decrease the long-term risks of something we humans are still sensitive to - radiation exposure.