DOI:10.2214/AJR.06.0886
AJR 2007; 188:966-969
© American Roentgen Ray Society
Impact of 3D Sonography on Workroom Time Efficiency
Jeffrey Hagel1 and
Simon G. Bicknell2
1 Department of Radiology, University of British Columbia, Rm. 335-0950, West
10th Ave., Vancouver, BC, Canada V5Z 1M9.
2 Department of Radiology, Lions Gate Hospital, Vancouver, BC, Canada.
Received July 6, 2006;
accepted after revision October 4, 2006.
Address correspondence to S. G. Bicknell
(sbicknel{at}interchange.ubc.ca).
Abstract
OBJECTIVE. The purpose of this study was to determine the effect on
workroom time efficiency of the 3D sonographic technique compared with the 2D
technique in examinations of the kidney, shoulder, small parts (thyroid,
testes, Achilles tendon, other superficial structures), and female pelvic
organs in a community hospital.
SUBJECTS AND METHODS. A random sample of 23 patients underwent
consecutive 3D sonographic examinations on a single day. Another random sample
of 40 patients underwent consecutive traditional 2D sonographic examinations
the next day. Both cohorts included a mixture of patients who underwent
shoulder, renal, small-parts, and pelvic scans. The 3D shoulder examinations
were followed by direct examination by a radiologist using the traditional 2D
technique to confirm the diagnostic accuracy of the 3D technique. The mean
times that patients were in the sonography room for 2D and for 3D sonography
were recorded and compared by use of a two-sample Student's t
test.
RESULTS. The mean time per examination for the 3D cohort was 11.48
± 3.55 minutes (SD). The mean time per examination for the 2D cohort
was 25.30 ± 11.64 minutes. Results of a two-sample Student's t
test showed the times for the two groups were statistically different
(p < 0.001). No diagnoses made with 3D shoulder sonographic
findings were changed when the shoulders were reevaluated directly by
radiologists using conventional 2D sonography.
CONCLUSION. This study showed significantly better workroom time
efficiency with use of 3D sonography than with traditional 2D sonography in
pelvic, renal, small-parts, and shoulder examinations in a community hospital.
These findings suggest that in the correct clinical setting, adopting 3D
scanning protocols may greatly improve patient throughput.
Keywords: musculoskeletal imaging • 3D sonography
Introduction
Three-dimensional volume sonography is a relatively new technology
that is finding its way into daily clinical practice. Numerous case reports
and studies with small numbers of subjects have shown the technique is an
effective adjunct to traditional 2D sonography in a variety of situations
[1-3].
However, results of studies by Benacerraf et al.
[4-6]
suggest that 3D sonography may be most useful as a standalone technique that
eliminates the need for time-consuming preparatory 2D sonography. These
studies have shown significant improvement in workplace efficiency when 3D
sonography is used in obstetric screening and transvaginal gynecologic
studies. To our knowledge, no studies published to date have documented
similar improvement in workplace efficiency with use of the 3D technique in
sonographic examinations of other anatomic regions. Neither, to our knowledge,
have studies been performed in a community hospital to confirm that 3D
sonography improves workplace efficiency in this clinical setting. The purpose
of our study was to compare the sonography workroom time efficiency of the 3D
technique with that of the 2D technique in renal, shoulder, small-parts
(thyroid, testes, Achilles tendon, other superficial structures), and female
pelvic examinations in a community hospital.
Subjects and Methods
Patients
A random sample of 23 patients underwent consecutive 3D sonographic
examinations on a single day. Pelvic, renal, small-parts, and shoulder scans
for a variety of indications were included with no selection criteria. No
vascular (venous or arterial) work was included because we had not finalized
these protocols given the complex nature of including relevant color and
pulse-wave Doppler techniques in volume acquisitions. Four sonographers with
1-25 years of experience performed the 3D scans according to a predetermined
protocol (Table 1). Limited 2D
images were included in the protocols to avoid more time-consuming
measurements on the 3D workstation. These 2D images included
anteroposterior-transverse and sagittal dimensions of the major organs
analyzed. Except for those undergoing shoulder scans, the patients were
discharged immediately after the examination and before review by a
radiologist. The time from the patient's entrance into the sonography room to
exit from the room was measured.
Another random sample of 40 patients underwent consecutive traditional 2D
sonographic examinations on a second single day. Pelvic, renal, small-parts,
and shoulder imaging with no selection criteria were included. A traditional
set of 2D images was obtained by the sonographers. The sonographers then
awaited review with one of four radiologists. Examinations on both days were
performed with Logiq 9 (GE Healthcare) machines. Linear 5- to 12-MHz
transducers were used for the shoulder and small-parts examinations. Convex 2-
to 5-MHz transducers were used for the renal and pelvic examinations.
Institutional review board approval was not obtained or needed for this
prospective study, but Declaration of Helsinki principles were followed.
Sonographic Interpretation
The 3D scans were reviewed by one of four general radiologists with 4-30
years of sonographic experience, each of whom had undergone a 2-hour tutorial
on use of the 3D workstation. Each 3D shoulder sonographic examination was
followed by a traditional 2D examination by one of the four radiologists for
confirmation of diagnostic accuracy. This additional time was not measured.
The scans were reviewed on a dedicated PACS with use of a dedicated 3D
workstation (Logiqworks, GE Healthcare) as required. The time to review the
studies and dictate the report was recorded. A subjective evaluation of
sonographer satisfaction with the 3D sonographic technique was logged.
Radiologists reviewed the primary 2D images and decided whether they needed to
scan the patient themselves or request additional imaging by a sonographer.
Once the examination was complete, the patient was discharged, and the time
from patient entrance to exit was recorded.
Statistical Analysis
Normality of the 2D and 3D cohorts was tested with the Anderson-Darling
normality test. Equality of variance between the 2D and 3D groups was tested
with the F test. The mean times patients were in the sonography room
were compared for the two cohorts by use of a two-sample Student's t
test. Statistical significance was considered p < 0.05.
Results
The 3D cohort included the mixture of study types shown in
Table 2. The mean time per
patient in the sonography workroom for the 3D group was 11.48 ± 3.55
minutes (SD) (Fig. 1A). In
addition, the mean time for review of the 3D volume set and dictation of the
report by one of four general radiologists was 67 seconds. In no cases did the
radiologist consider the organ or region in question incompletely imaged. In
no case was it necessary to call the patient back for additional direct
evaluation by a radiologist. The diagnosis initially made after review of the
3D volume set from the shoulder examinations was not changed in any case when
the patient was later directly examined by a radiologist in the traditional 2D
manner.
The 2D cohort included the mixture of study types shown in
Table 3. The mean time per
patient in the sonography workroom for the 2D group was 25.30 ± 11.64
minutes (Fig. 1B). Therefore,
3D scanning resulted in a net time savings of 13.82 minutes per patient, only
45.4% of the time taken for traditional 2D sonography. The technologists
reported a high level of satisfaction with the 3D scanning method
(Fig. 2).
Normality of the 2D and 3D cohorts was verified with the Anderson-Darling
test (p <0.05), and equality of variances was confirmed with the
F test (p < 0.05). Comparison of the mean time per
patient for the 2D group (25.30 minutes) and that for the 3D group (11.48
minutes) by use of a two-sample Student's t test showed a
statistically significant difference (p <0.001).
Discussion
Three-dimensional sonography is a technology that involves acquisition of
sonographic volumes as opposed to the single tomographic slices traditionally
viewed on 2D sonography. This volume set can be displayed as a sweep through
the volume in the same plane as the original acquisition. In addition, it can
be displayed as surface-rendered, maximum rendered, and multiplanar images
reconstructed in any plane desired. Current reconstructed images have lower
spatial resolution than in-plane images (Figs.
3A,
3B,
3C and
4A,
4B,
4C), but as the technology
continues to advance and matrix probes become available, this weakness will
likely be resolved [5].
Three-dimensional sonography has been shown to be a useful adjunct to 2D
imaging in areas such as obstetric, gynecologic, abdominal intervention, and
abdominal sonography
[1-3].
View larger version (116K):
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Fig. 3A —35-year-old woman with medullary nephrocalcinosis secondary to
medullary sponge kidney with mild right hydronephrosis. Comparison of spatial
resolutions. Sagittal 2D sonographic scan obtained as static image with
conventional technique.
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Fig. 3B —35-year-old woman with medullary nephrocalcinosis secondary to
medullary sponge kidney with mild right hydronephrosis. Comparison of spatial
resolutions. Sagittal 2D sonographic scan obtained from sagittally obtained
volume.
|
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Fig. 3C —35-year-old woman with medullary nephrocalcinosis secondary to
medullary sponge kidney with mild right hydronephrosis. Comparison of spatial
resolutions. Sonographic scan obtained with sagittal reformatting from
transversely acquired volume.
|
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Fig. 4A —55-year-old man with acute full-thickness tear of supraspinatus
tendon. Comparison of spatial resolution. Sagittal oblique sonographic image
of left shoulder obtained with conventional 2D technique shows tear (white
arrows).
|
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Fig. 4B —55-year-old man with acute full-thickness tear of supraspinatus
tendon. Comparison of spatial resolution. Sagittal oblique sonographic image
from sagittally obtained volume shows tear (white arrows).
|
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Fig. 4C —55-year-old man with acute full-thickness tear of supraspinatus
tendon. Comparison of spatial resolution. Three-dimensional surface-rendered
image in transverse plane reconstructed from sagittally obtained volume shows
tear (white arrows). Black arrows indicate volume averaging through
humerus; asterisk indicates humeral head.
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On CT and MRI, cross-sectional and volume data are acquired, and in most
cases the patient is discharged before a radiologist reviews the images. The
advent of 3D sonogra- phy should allow a similar protocol for many types of
sonographic imaging and indications. This ability was tested in preliminary
studies by Benacerraf et al.
[4-6],
who found significant improvement in workplace efficiency when 3D technology
was implemented in obstetric screening and transvaginal examinations. Those
investigators found that the time to perform and interpret an obstetric
screening sonographic examination with their 3D method was less than one half
that required for the traditional 2D method
[4,
5]. They also found that 3D
transvaginal sonography and interpretation are significantly more time
efficient than traditional 2D sonography with equivalent accuracy between the
techniques [6]. Nelson et al.
[7] found that for pelvic,
abdominal, and obstetric scans it is feasible and accurate to acquire 3D
sonographic data at one site and review them offline at a second site. They
did not, however, report the time to acquire their 3D and 2D scans.
The results of our study suggest that 3D sonography may allow significant
improvement in workroom time efficiency when implemented for pelvic,
small-parts, renal, and shoulder scans. Our results show that a 3D sonographic
examination can be performed in 45.4% of the time required for an equivalent
traditional 2D sonographic examination. The actual scanning times for the two
techniques were similar. The 3D protocols took 11.5 minutes, and the
traditional approach took 13.6 minutes. The significant time savings occurred
after scanning. The 3D data set eliminated the need for sonographers to review
their images and await review with a radiologist. It also eliminated the need
for a radiologist to directly scan the patient. Elimination of these steps in
our 3D protocol resulted in a cumulative mean savings of 13.8 minutes per
case. Since the study, we have added an additional sagittal oblique volume for
shoulder studies but use the traditional 2D setup. Small partial-thickness
tears can be difficult to see with the lower-spatial-resolution 3D acquired
volume. Although the 2D volume cannot be reconstructed, the acquired plane of
resolution is better than the in-plane resolution of the 3D technique.
The four sonographers participating in this study preferred the 3D
protocols over traditional 2D technique
(Fig. 2). They also
subjectively believed that they were able to discharge patients in a more
timely manner and that in more complex cases they would be able to discharge
patients without waiting for radiologist review.
Potential weaknesses of this study were that because it was performed at a
single community hospital, the results may not apply to centers with other
patient populations. This factor is important because tertiary care hospitals
have patients with complex findings, and therefore the time savings may not be
as great as those in the community hospital. In addition, except in the
shoulder examinations, we did not confirm the 3D interpretations with
traditional 2D imaging, thus the accuracy of 3D technique was not fully
evaluated. In each case, however, the volume set included the entire region of
interest. Having viewed the entire area ourselves, we were subjectively more
confident in our 3D interpretation than we were in traditional review of
selected 2D images. Finally, current 3D reconstructions are made at dedicated
workstations specific to different manufacturers, thus departments with a
mixture of brands of equipment would need several dedicated workstations.
Although further investigation is needed, we believe our findings suggest
that use of 3D sonography can greatly improve workroom efficiency for a
variety of indications in community hospitals. At our institution, we continue
to use 3D protocols with significant time savings for pelvic, renal,
small-parts, and shoulder examinations. As we gain experience and confidence
with this technology, we continue to alter and refine our booking schedules
and increase patient throughput.
Acknowledgments
We thank Zahava Uddin for assistance with the statistical analysis.
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Abstract
Introduction
