Direct Digital X-Ray

Digital Radiography (DR) was demonstrated at the Radiological Society of North America’s (RSNA) annual meeting as early as 1996, and now it is finally here in a big way. We have waited patiently (or not) these 10 years for manufacturers to make digital imaging truly available and attainable. Now, the technology is becoming ubiquitous, both as nomenclature and as a deliverable product.

In 1998, the first DR general radiology units—simple units with fixed geometry and limited applications—cost $350,000 to $450,000. In 2005, the cost ranged from around $199,999 for a simple manually articulated c-arm to $450,000 for models with robotic “follow me” technology. With these advanced electronic positioners, the ceiling-mounted tube automatically follows the detector plate, adjusts focal distance, and opposes the detector at 90°. These units can also provide electronic tomographic coupling.

Some facilities have taken the position, “If it ain’t broke, don’t fix it,” and continue to use their film-based equipment, and the required darkrooms, as long as it keeps working. Other facilities have used computed radiography (CR) as a bridge to digital acquisition and storage, and have eliminated the darkroom and film costs. When the CR equipment is depreciated at these facilities, it will probably be replaced with DR equipment.

The most progressive facilities are buying digital systems to improve efficiency and reduce the total number of x-ray rooms and staff required. The cost of staffing two CR-based x-ray rooms, along with the cost of maintaining both the x-ray and the CR equipment, makes replacing two conventional x-ray rooms with a single digital room a very budget-friendly choice.

Installed systems have proven their efficiency by delivering images in 3–6 seconds after exposure. Room-turnover rates can improve from five to six exams per hour with film or CR equipment, to 10–15 exams with DR equipment. Patient recalls for repeat exams can almost be eliminated by reviewing images before subjects leave the exam room, and by completing any subsequent exposures immediately.

Mountings for the x-ray-tube imaging system range from the simple c-arm to the more conventional pedestal and ceiling-rail mounts. Mountings for the detector plate range from a single plate on a c-arm, pedestal, or undertable, to dual plates with one undertable and another mounted on a pedestal or from a ceiling rail. Digital detectors have even made their way to portable x-ray, including a model with a digital-detector plate and wireless transmission to a picture archiving and communication system (PACS).

The detector technologies competing to establish themselves as the gold standard include charge coupled devices (CCD), camera chips, amorphous silicon plates, and amorphous selenium plates. The jury is still out on which will become the de facto detector, as each of the three technologies brings its own unique set of advantages. For the moment, it seems that CCD is in the driver’s seat in terms of pricing, as its initial acquisition cost is lowest and the cost of replacing CCD chips is less than the cost of replacing silicon or selenium plates.

What does the implementation of DR equipment mean to the biomed department? Radiology equipment is conforming with the rest of what you already do. There are more and more electronic components, and consequently fewer and fewer photographic and mechanical technologies, for you to deal with. Sure, you will still want to receive manufacturers’ training and certification, but that training will be more consistent with the training you receive for other technologies, such as patient monitoring. Bringing electronics into the standard x-ray room also brings online diagnostics support from the manufacturer. Using the manufacturer’s remote online support, biomed service engineers can very effectively provide the first level of response to keep DR systems up and running.

After we have captured the images digitally, the next thing we will need to learn is how to make them flow through PACS and appear as a component of the electronic medical/health care record on the bedside patient monitor. That will be demonstrated at the Health Care Information and Management Systems Society meeting in San Diego, February 12–16, 2006. 24x7

Ric Heerwald is principal at Planning Resources, an equipment- planning consulting practice located in Richardson, Tex.