As picture archiving and communicattion systems (PACS) technology has matured, radiologists have discovered that reading images on screen offers many advantages. With digital access, as well as image enhancement and manipulation tools, soft-copy images aid in determining accurate diagnoses.
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
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
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."