Mr. Fillicelli is the Manager of Clinical Marketing for the Health Imaging Division of Eastman Kodak, Rochester, NY.

For years, film has been the gold standard for diagnosis. As picture archiving and communication systems (PACS) technology has matured, radiologists report that reading images on a monitor offers new capabilities that outweigh film's resolution advantage. These systems offer the convenience of digital access and image enhancement and manipulation tools. Interpreting images on a full-featured diagnostic workstation allows radiologists to render an accurate diagnosis with confidence.

Gregory D.N. Pearson, MD, is assistant professor of radiology at Columbia University and works in the thoracic radiology section of the Columbia Presbyterian Center of New York Presbyterian Hospital, New York, NY. He reports that digital workstations can provide specific information that is difficult or impossible to glean from a hard-copy image.

He cites a tool that allows him to measure density in Hounsfield units as an example. These density readings can be used to detect fat or diffuse calcification in a lung nodule, which indicates that it is benign. "Being able to precisely measure density provides me, and referring physicians I serve, with a higher level of confidence. There is a huge difference between 'indeterminate pulmonary nodule' and 'The density of the lesion indicates that it is benign.' Because the former diagnosis is not conclusive, the patient usually needs to be brought in for follow-up testing or even biopsy. Before PACS, we would have to do these measurements at the CT scanner or have the CT technologist transfer the images to a remote console. This would often cause patient delays."

Measuring the size of a lesion is also much easier. "An image can be blown up to full screen and digital calipers can be placed so that the workstation calculates the distance. When measuring on a hard-copy image, we would usually use a piece of paper to mark off the size of the lesion and then compare to a centimeter scale printed on the side of the film. For a small lesion printed with 20 images on a sheet, the width of the pencil line could easily add several millimeters. The digital technique is far more accurate and reproducible."

Digital tools can also help radiologists deal with images of different orientations. Radiologists can track suspicious anatomy by applying "scout lines" that allow the area to be located quickly on other views. "Sometimes you lose the area you are examining when you change from the sagittal to the coronal image, for example. If you can't localize a nodule, it's extremely difficult to diagnose," Dr. Pearson explains.

He recently applied this technique to a cardiac MRI image in which turbulent flow was noted in the right atrium. "By placing a scout line over the area and looking at other views, I was able to determine that the flow was not due to an atrial septal defect, but to inflow from a persistent left superior vena cava."

Preset windows handle density differences

Applying "windows" also allows radiologists to examine areas of an image with differing densities efficiently. "It's very convenient to be able to view CT images in lung, bone, and soft-tissue windows with standardized, preset parameters. The same image can be viewed in different windows simultaneously side-by-side. This technique allows me to quickly review each area of the anatomy at ideal levels of contrast," notes Dr. Pearson. "Window adjustments can also be made manually to better view light or dark regions of a chest film. It's far more useful than a bright light in improving contrast."

Interpreting studies on a diagnostic workstation offers other advantages as well. Ronald Fadell, MD, a neuroradiologist at Kettering Medical Center in Dayton, OH, is pleased with the cineloop feature and the ability to view side-by-side displays of current and comparative studies.

"The cineloop offers tremendous advantages when viewing small tumors and subtle anatomy in CT and MR studies. It allows me to fix my eyes on the area of interest, as the workstation scrolls through images. This technique can make a tremendous difference when I am trying to study tiny nodules in the lung, and for examinations of the brain and spine."

Comparative study provides advantages

Ready access to previous studies of the same and differing modalities is also a tremendous advantage, Dr. Fadell notes. "Comparison is one of the most valuable techniques in radiology. With digital imaging, these past studies are immediately accessible. Retrieving film studies is much more difficult and time consuming, and the studies are not always available."

Dr. Fadell frequently uses on-screen, side-by-side comparisons of current and previous studies to resolve challenging cases. "Scrolling through each study in a side-by-side comparison is a much more efficient and accurate method of following tiny nodules than looking at film studies on large display boxes," he says. "I can also verify that the settings are the same for each study on the workstation, whereas I can't make any adjustments to film images."

Adjusting exposure settings helps radiologists

Dr. Pearson notes that another tremendous advantage of digital imaging systems is the compensation algorithms that "correct" images that are over- and under-exposed.

"I attended a Grand Rounds presentation in which the speaker, Dr. Carl Raven of Duke University, highlighted how difficult it is for radiologists to take into account differences in imaging technique. For example, if we see a darker image, we tend to believe that a pulmonary edema is getting better--when it may just be a difference in exposure. Images that are corrected and consistent can greatly improve diagnostic accuracy."

One radiologist noted that not all diagnostic workstations are created equal. When Joel E. Janousek, MD, accepted a radiology position at Wilson Memorial Hospital in Sidney, OH, he immediately noticed a difference in the reading room. "The PACS workstations I used at my previous institution were very simple and easy to use, but they did not offer many of the features that optimize reading from soft copy," he notes. "I believe that a four-monitor diagnostic workstation, in combination with these enhanced features, provides me with tools that are critical to making an accurate and efficient diagnosis."

While PACS may offer convenience and efficiency, it is up to radiologists to evaluate and document the impact of digital imaging on patient care. Clinical studies are being conducted to measure the accuracy and sensitivity of diagnoses from soft copy compared with film images. Preliminary data indicate, and radiologists confirm, that full-featured diagnostic workstations provide excellent tools for rendering accurate diagnoses, in addition to the well-documented advantages offered by the digital storage and access of PACS.

The improvements in patient care that digital imaging and on-screen interpretation can offer are beginning to be documented. According to Dr. Charles Marn, radiologists working with PACS "have quickly come to recognize the relationship between high-speed communication, novel and convenient methods of image management and manipulation and the overall quality of care in our institutions." ¹