PACs Systems and digital imaging

For the past 10 years the evolution of PACs systems have been impacting how medical equipment planners approached the planning of hospitals. These changes started with the shift away from designated dark rooms for x-ray film processing. While that space was reclaimed into the department, additional devices have filled that footprint. Image plate readers and laser printers are able to produce hard copy x-ray films and share these images in a digital format with others without the need for dedicated darkrooms. While the overall space requirement of the equipment has not been reduced, its ability to be in an open lighted area has certainly freed-up space that would otherwise have been dedicated to the darkroom. A healthcare architect should look to a medical equipment planner for insight into trends and technologies that will impact the space requirements of each project. Even if a medical equipment planning consultant is not on-board the project yet, it is a good idea to have firm on retainer to ask questions during the initial space planning and schematic design phases.

To understand the shift from traditional x-ray film to a hospital PACs system, try thinking of a digital camera versus a traditional film camera. The benefit of having your image in a digitized format allows you to share it via the web or other computer network quickly and easily. It is important to note that the PACs system ( Picture Archival and Communication) is a system, not a specific device. There are several components, each having an impact on the cost and efficiency of the overall system.

The goal of digital imaging is to offer much faster access to the images. This speed is represented in 2 ways, first in the acquisition of the image and second, in the sharing of the image.

Step 1 is image acquisition. For this there are 3 possibilities. First, conventional film. Second, CR or computer radiography and third, DR or direct digital radiography.

The analogy of a film camera versus a digital camera is easy for most of us to imagine. In the tradition process, film had to be developed before the image could be seen. In CR, the x-ray image is acquired on a plate and then processed in a "Plate Reader". There is only a slight speed advantage between traditional film processing and CR. Here is a rather fun video that compares traditional film processing to the CR Plate reader method.




You can see from the video that the CR is slightly faster. This method of digitizing the image still requires the plate (The digital imaging version of a memory card) to be inserted into a machine (Plate Reader) to be viewed on a computer screen. By contrast DR, or direct digital radiography, offers instantaneous access to the image. As the x-ray is taken, the image is captured and displayed directly from the x-ray device. In DR, there is no additional step of running a plate though a reader.

An x-ray tech must view the image before the patient can be excused (Usually). This allows them to confirm the x-ray quality was good (Patient position & exposure). With CR, the image is delivered to a monitor after it is passed through a reader. In DR, the image display is instantaneous. This allows the technician to know immediately if the x-ray taken was of sufficient quality to allow the film to be "read" by a radiologist. The patient can be excused and the room prepared for the next patient.

After the acquisition phase, the sharing/distribution/communication of the image will benefit greatly from the digital version of both CR and DR. Rather than needing to hand deliver a developed x-ray film back to the radiologist or tech, the images are available on-screen. This is of tremendous benefit when the referring physician, radiologist, and imaging tech all need copies.

A hard copy x-ray film can be passed though a scanner to become digitized. Today this is common for retrieving old patient x-rays. Typically the x-rays are kept on file for 7 years if an adult and until the age of 21 if a minor. That means there are a lot of hard copy films in storage. Because many of these films (OK, most) are never going to be pulled, it would be a wasteful exercise to convert all of them to digital.

What typically happens is a request to retrieve an old x-ray film is made, the film is pulled and scanned into a digital file. This x-ray film is now a part of the PACs system and can be distributed accordingly. As old x-ray films are no longer required to be stored, they are destroyed and the storage space can be converted to other uses.

So to recap:

Traditional x-ray images were created in film, the film was developed, and the hard copy film was available to be hand delivered or duplicated as needed.

CR, or computed radiography, allowed the x-ray image to be stored on a "Plate" and read into a digital file on the PACs network. The CR system still required the plate to be manually loaded into the device, creating a lag time between the time of the x-ray and when the plate was transported and loaded into the reader.

DR, or direct digital radiography, allows the image to be captured into the PACs system and visible to the tech, radiologist or doctor at the moment the x-ray is taken. This greatly streamlines the process.

Both CR and DR allow the image to be sent via electronic means. The limiting factors are access to a computer and a monitor with sufficient resolution. In most cases, the monitor resolution is only a factor for the radiologist who is looking for very subtle variations, such a cancer screening in mammograms, etc. A broken bone will appear easily on the monitor you are using to view this blog.

The added benefit of PACs is the reduced need for storage of hard copy x-rays. The existing stores of x-ray film are being purged a little more each year as the required holding period for the films expires.

The cost of the technology to acquire, store and share digital x-rays is high as compared to the traditional methods. This meant that the technology was implemented only in the areas where it could be cost justified. The imaging department, ER and ICU were about the only place you might find a PACs viewing monitor or plate reader. Today, the cost of the systems have come down and the original investment in the technology has allowed for a small incremental investment to move the technology into other departments and even off-site locations.

The traditional x-ray viewbox (Illuminator) will eventually be phased out in much the same way as the darkroom has been. As a medical equipment planner, the important task is to understand the clients need at building occupancy, but also in the future. Making sure that there is a clear migration path for PACs stations to replace the x-ray viewboxes is just one example of where medical equipment planning makes a project more efficient. An architect has a tremendous volume of codes, regulations and client expectations for simply designing the 4 walls, floor and ceiling or each room. The medical equipment planners insight into how technology changes will impact the work flow and space requirements is of critical importance. When selecting your medical equipment planner, make certain they are involved early with the architectural design team.