AJR 2002; 179:575-577
© American Roentgen Ray Society
Review and Interpretation of MR Imaging Studies with PACS: Creating Uniform Series Descriptors for Radiologists and Referring Physicians
Lawrence H. Schwartz1,2,
Peter Kijewski1,2,3,
Kate Lynch1,
Eric Lis1,2 and
David M. Panicek1,2
1 Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York
Ave., New York, NY 10021.
2 Department of Radiology, Weill Medical College of Cornell University, New
York, NY.
3 Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New
York, NY 10021.
Received September 17, 2001;
accepted after revision February 21, 2002.
Address correspondence to L. H. Schwartz.
Abstract
OBJECTIVE. We sought to identify a limited set of standardized
descriptors for various MR image series on a picture archiving and
communications system (PACS) and to apply these descriptors to both existing
and newly acquired MR images.
CONCLUSION. Of the 47,028 MR image series in our PACS, approximately
2500 had been assigned unique descriptors, and nearly 82% of the descriptors
had a frequency of appearance of less than 5%. We reduced the number of
descriptors to 146 without loss of essential information. Use of standardized
descriptors may facilitate identification of various MR image series.
Introduction
The interpretation of MR images on a picture archiving and communications
system (PACS) presents specific logistic challenges because of the various
anatomic planes and pulse sequences in which the multiple images are obtained,
often before and after administration of contrast materials. The subset of
those images obtained with identical imaging parameters (e.g., sagittal
T1-weighted fat-suppressed gradient-echo images obtained after IV gadolinium
administration) constitutes an image series in a PACS. The concept of the
image series is well understood by most radiologists but not by many referring
physicians. Referring physicians who use PACS need to navigate through
multiple image series to view an entire MR imaging study. Even if optimized
default display arrangements of images on PACS are used
[1], switching among various
image series is often necessary; this process may be confusing and more
challenging than using films, especially if a wide range of descriptive labels
is used to name the various image series in the PACS.
To facilitate the manipulation of various image series by both radiologists
and nonradiologist physicians, we designed a standardized list of relevant MR
image series descriptors that could be easily understood. We then converted
the existing MR image series descriptors in our PACS to this standardized
nomenclature. Our standard protocols in the MR imaging scanners also were
updated to reflect this list.
Materials and Methods
We determined the number and frequency of appearance of all unique image
series descriptors from the 47,028 MR image series that had been transferred
from the MR imaging console to our PACS (PathSpeed, version 7.12; General
Electric Medical Systems, Milwaukee, WI) at the time of image acquisition. The
image series descriptors used in the existing standard MR imaging protocols
were also analyzed. A subset of standardized image series descriptors was
subsequently created, and the image series descriptors for all existing MR
imaging studies in our PACS were converted to these standardized descriptors.
For example, the terms "T1 axial," "axial
T1-weighted," "T1 ax," "ax T1," and "T1
spin-echo axial" were all changed to "axial T1." These
standardized image series descriptors also were entered at the MR imaging
console into the appropriate database field and then were mapped to the
appropriate DICOM (Digital Imaging and COmmunications in Medicine) database
elements so that all subsequent MR imaging examinations sent to the PACS would
contain only these standardized image series descriptors.
Results
Of the 47,028 MR image series present in our PACS, 1977 (4.2%) did not
contain a series descriptor: There were 2544 unique series descriptors, of
which 2077 (81.6%) had a frequency of appearance of less than 5%. The five
most commonly used series descriptors occurred in only 20% (9436/47,028) of
the series.
We defined 146 standardized series descriptors to replace the existing 2544
unique series descriptors in PACS—a 94.3% reduction in the number of
series descriptors. After conversion to the standardized nomenclature, the
five most frequent series descriptors, used in 40.7% (19,148/47,028) of the
series, were "axial T1," "localizer," "axial
T2," "sagittal T1," and "axial T1 post." Our
typical naming convention for series descriptors was to select two or three
words beginning with the plane of acquisition, the tissue weighting, and
sometimes a descriptive term related to contrast administration, special
location, or other MR imaging parameter, such as fat suppression.
Discussion
Although a PACS can facilitate information flow within a health care
enterprise [2,
3], inefficiencies can result
from suboptimal implementation of various processes within a given PACS system
[3,
4]. After our PACS had been
operational for approximately 1 year, we found that a plethora of image series
descriptors for MR imaging examinations had been recorded, having been created
by the various technologists performing those examinations. Although
radiologists could generally decipher the meaning of most of those
descriptors, some (e.g., FMPSGR [fast multiplanar spoiled gradient-recall],
FLASH [fast low-angle shot], FISP [fast imaging with steady-state free
precession], and SSFSE [single-shot fast spin-echo] among others) remained
obscure. Nonradiologists physicians also reported difficulty in navigating
through multiple MR image series, and some physicians were unfamiliar with the
more technical descriptions used in various image series descriptors.
In designing standardized image series descriptors, a balance needs to be
reached between providing sufficient technical detail and maintaining
simplicity. For example, radiologists who are involved in MR imaging better
understand the implications of pulse sequence names (e.g., single-shot fast
spin-echo or gradient-echo) than do most nonradiologist physicians. Therefore,
we chose to exclude most pulse sequence names from the descriptors (with STIR
[short tau inversion recovery] being one exception). Instead, more generic
phrases such as "T2-weighted" or "opposed-phase" were
used. Similarly, some image series descriptors were based on the specific use
of a sequence to image a certain body part, such as "coronal MRCP"
(MR cholangiopancreatography), rather than "coronal T2-weighted
SSFSE" (Fig. 1). Of
course, all the technical parameters involved in producing the images (such as
TR, TE, and flip angle) still need to be available to the radiologists (and
other interested physicians) elsewhere in the PACS, even though they are not
currently part of the image series descriptor in our PACS. (In an earlier
version of the PACS, the image series descriptors had consisted of a confusing
concatenation of technical parameters, including TR, TE, flip angle, imaging
plane, and pulse sequence.)
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Fig. 1. —Single-monitor PACS display shows four different MR images
from four different series of one examination in 81-year-old man with cystic
pancreatic mass diagnosed as adenocarcinoma. Entire list of available series
of images from this patient's examination is also displayed. User may display
one or more available series by highlighting it on list. Note that a check
mark precedes name of each series displayed on monitor.
|
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In some cases, the same pulse sequence had more than one image series
descriptor, which was based only on the region being scanned. For example, an
SSFSE pulse sequence might have been labeled as "coronal MRCP" if
it had been performed to evaluate the liver and biliary tree, but
"coronal MR urogram" if it had been performed to evaluate the
urinary tract. These specific image series descriptors are readily
identifiable by referring physicians who treat conditions of the biliary tree
and urinary tract, respectively, without the use of confusing MR imaging
jargon.
As new pulse sequences are introduced or new protocols are designed, we
will incorporate any additional series descriptors to maintain consistency
with our naming scheme. Similarly, although standardized series descriptors
are written into all standard protocols in the MR scanners, occasionally a
nonstandard sequence is manually entered into the scanner. To address that
circumstance, our MR imaging technologists are made aware that they should
select a descriptor for that series only from the standardized list. Different
manufacturers use different series descriptors for similar pulse sequences,
thereby potentially complicating the naming of series descriptors. Although
our institution has MR equipment from only one manufacturer, we chose series
descriptors that are generic and could be applied to other manufacturers'
equipment as well.
Besides facilitating physician review of MR imaging examinations on a PACS,
standardized image series descriptors also are critical for implementing
standardized default display protocols
[1]. For example, a user of our
PACS can set the default display for MR images of the liver so that the
unenhanced axial in-phase gradient-echo image series will always appear in the
upper left portion of the PACS monitor and the axial fast spin-echo
fat-saturated T2-weighted images in the upper right. For this proper placement
to occur automatically, the image series must have appropriate series
descriptors attached to them to allow their accurate recognition by the
PACS.
This process of developing and implementing standardized MR image series
descriptors should be readily applicable to any PACS system. It could also be
used for other imaging modalities; for example, it could be used to label the
various phases of multiphase CT of the liver or the different phases of a
triple-phase bone scan.
We were able to reduce the number of image series descriptors by more than
94%, leaving only 146 unique descriptors. Because most of the descriptors
include specification of the imaging plane (such as axial, coronal, or
sagittal), the number of unique descriptors after specification of plane is
fewer than 50. This smaller range of image series descriptors will be less
confusing to all who must navigate through the multiple image series in a
typical MR imaging examination. These descriptors can be thought of as the
electronic equivalent of the small paper labels identifying the image series
that some facilities attach to each sheet of an MR imaging examination.
Moreover, the set of standardized descriptors facilitates implementation of
default display protocols on the PACS.
Further work is needed to assess the effect of a reduction in series
descriptors on diagnostic performance of radiologists and referring
clinicians. Certain user preferences may emerge as the effect of uniform
series descriptors is analyzed and the impact on physician efficiency is
assessed.
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Abstract
Introduction
