Ultrasound imaging has the advantages of being a real-time, multiplanar, nonionizing radiation imaging technique. However, the technique is limited by operator dependence [1, 2]. While other imaging modalities such as computed tomography, magnetic resonance imaging, and nuclear medicine adjust parameters to improve image quality and diagnostic information, these are usually standardized and programmed before the start of the examination. These parameters are used without change throughout the data acquisition. However, in ultrasound, the interaction of the sound beam with the patient varies significantly throughout the course of a standard examination.
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Dr. Richard G. Barr
is a Professor of Radiology at Northeastern Ohio Universities
College of Medicine (NEOUCOM) and is Director of Ultrasound,
Forum Health, Western Reserve Care System
Ultrasound imaging has the advantages of being a real-time,
multiplanar, nonionizing radiation imaging technique. However, the
technique is limited by operator dependence [1, 2]. While other
imaging modalities such as computed tomography, magnetic resonance
imaging, and nuclear medicine adjust parameters to improve image
quality and diagnostic information, these are usually standardized
and programmed before the start of the examination. These
parameters are used without change throughout the data acquisition.
However, in ultrasound, the interaction of the sound beam with the
patient varies significantly throughout the course of a standard
examination. The sonographer therefore must adjust parameters
continuously throughout the examination to optimize the image [3,
4]. There are multiple operator-dependent controls used to optimize
the image in ultrasound [5]. Some of these are difficult and
time-consuming to optimize. To overcome this limitation, ultrasound
manufacturers have developed an automated optimization technique
whereby with the push of one button, the image is optimized by the
computer operating system. This technique is available from several
manufacturers [6]. This technique decreases the number of buttons
that must be adjusted to optimize an image. The technique corrects
all of the most common technical errors in ultrasound, including
unbalanced gain, undergained or overgained images, and refractive
shadowing. This technique also has the capability of optimizing
some parameters that are not available for the operator to adjust,
such as lateral gain. However, these techniques optimize only a
single image, and the scan is no longer optimized as soon as the
probe is moved. This technique of image optimization has also been
developed to manually optimize and present Doppler information
(Figure 1; Online video clip 1)
.
Native TEQ Technology
As opposed to TEQ ultrasound technology, which optimizes a
single image, Native TEQ™ ultrasound technology (NTEQ) has been
developed as a real-time technique to adjust the gain as well as
other parameters while scanning. The computer is programmed to
perform advanced real-time motion analysis in addition to
accurately detecting and differentiating noise and artifacts from
soft tissue. The image gain is automatically optimized in the axial
and lateral dimensions in real-time, once the transducer touches
the patient or anytime it is moved to a new acoustic window. This
leads to several advantages. Image quality is optimized on the fly
with real time analysis every few seconds. The optimization
technique optimizes some parameters which the operator does not
have the ability to adjust and, as a result, the images are of
improved quality over that of manually adjusted images.
Additionally, there is a significant decrease in the number of
buttons adjustments a sonographer needs to adjust during the
examination, which improves overall ergonomics. There are no gain
or depth-gain-compensation (DGC) control adjustments needed while
scanning, and the technique removes operator dependence on the
adjustment of the scan, therefore providing a "standardized" image
that is independent of the operator and specific to each patient.
The technique can be used with other imaging techniques, such as
harmonic imaging and compounding.
The robustness of the technique can be demonstrated by manually
adjusting the initial image so the image is uninterpretable, and
then turning on the technique, and within a few frames, the image
is optimized
(Figure 2; Online video clip 2)
. Figure 3 demonstrates the technique during a routine scan of the
retroperitoneum. The image on the left (A) is a frame just before
an optimization, while the image on the right (B) is the frame
immediately after the optimization
(Online video clip 3)
. Note the improved image quality obtained without any manual
adjustments and the fact that there is a significant decrease in
the reverberation artifact in the cyst. Figure 4 demonstrates the
ability of the computer optimization to improve image quality over
manual optimization. The image in Figure 4A is a testicle manually
optimized. Note the refractive shadowing from the superior and
inferior poles of the testicle. Figure 4B shows the image that has
been optimized with NTEQ ultrasound technology. Note that the
computer has the ability to eliminate the artifact because of its
ability to control lateral gain. With the real-time optimization,
spontaneous flow is often noted in larger blood vessels.
Figure 5 (Online video clip 4)
illustrates the blood flow visualized in the inferior vena cava
(Figure 5B), which is not seen in the manually adjusted image
(Figure 5A). This is appreciated best in real-time imaging.
The operator can adjust overall image intensity, making it
brighter or darker for personal preferences. The rate at which
optimization occurs can also be adjusted for each user preference.
The technique is turned on with a single button and can be turned
off by manually adjusting the gains or turning the technique off.
In our experience, there are very few circumstances where using the
technique is not preferred. The technique can be used on all types
of examinations, and is available for all transducer types.
Where Is NTEQ Technology Useful?
We have found that the use of NTEQ ultrasound technology is
extremely helpful in the intensive care unit or neonatal care unit
settings. The sonographer no longer needs to be positioned with one
hand on the machine for manual image optimization and the other
hand with the probe on the patient. With the use of a foot pedal,
the sonographer can now move around the patient and obtain
optimized images with minimal need to adjust the system. Because
the system automatically adjusts gains, the images obtained are
uniform and appropriately adjusted for gain, independent of the
ambient light in the room. One can adjust the gain settings on the
monitor for visualization while performing the exam on the monitor,
and the system gains are appropriate for optimized images and final
review. In the operating room, one can scan with minimal need to
touch the system improving sterility during the exam. During
scanning in the operating arena, there is often limited space, so
the system can be hooked to an external monitor and placed distant
from the operating table with the use of a foot pedal for data
storage.
When performing real-time ultrasound-guided image biopsies, the
technique allows for rapid continued image optimization during the
procedure. As a result, there is no need for an additional
sonographer to be adjusting the system while the radiologist, with
a needle in one hand and the probe in the other, is performing the
biopsy. It is our preference to scan continuously through the area
of the biopsy as well as in the transverse plane to the needle
entering to confirm adequate placement of the needle in three
dimensions. This can be done with NTEQ ultrasound technology with
optimization of the images throughout the procedure. Another area
where NTEQ ultrasound technology is extremely helpful is what I
refer to as "dynamic anatomy." In those situations where anatomy is
moving, it is very difficult to manually adjust parameters to
optimize an image. The rapid optimization offered by the system
allows for significantly improved optimized images during the
examination and decreases the amount of lost information because of
the inability to optimize an image when the anatomy is in the best
window. This is most apparent when doing an OB ultrasound
examination
(Online video clip 5)
. The rapid image optimization allows for captured fetal anatomy
when the fetus is in an optimal window without the need for manual
adjustments during which time the window could have been lost.
In organs that vary in sonographic properties, the effect is
more apparent. In tissue, such as breast, where the sonographic
properties can vary greatly from fatty tissue to dense breast
tissue over a small area we find the technique allows for decreased
scanning time by eliminating the need for continuous gain
adjustments
(Online video clip 6)
.
Does This Mean Everyone Will Be Able To Perform
Ultrasound Now?
A major concern of sonographers is that the use of this
technique will allow less-trained personnel to perform ultrasound
examinations. In fact, I believe these techniques will empower the
sonographer to improve the quality of examinations and require
their anatomy and pathology training to be more critical. A
sonographer can now concentrate on the patient and his/her anatomy
and pathology, as opposed to button pushing. A sonographer can now
spend his/her time obtaining an optimal acoustical window,
positioning patients for the best image, and obtaining more
information from ultrasound imaging. Excellent images, while
missing pathology, are of no clinical use.
Ergonomics
In addition to providing improved image quality dynamically
throughout the examination, this technique should also decrease the
repetitive injury associated with ultrasound scanning. The
technique significantly decreases the number of key strokes
required to perform an examination. Personally, I believe that the
technique decreases the amount of back strain when trying to
maintain one hand on the console and one hand on the patient. One
can maintain a more comfortable position while performing the
examination. Our initial impression is that this also decreases the
time needed to perform an examination.
New Applications
Because the computer is performing the image optimization, the
images are more "standardized" than those created with manual
optimization. One would expect a significant decrease in the amount
of intra- and interscanner variation in images. To test this
hypothesis, we evaluated the intensities of objects in a phantom
scanned multiple times using NTEQ technology and the manual
technique. The results are tabulated in Table 1. The standard
deviations using NTEQ technology are all significantly smaller than
when performing manual adjustments. When one compares the uniform
areas of the phantom at different depths, the intensities of the
near and far field are all more uniform utilizing NTEQ
technology.
If we can confirm that the images are more standardized using
the NTEQ technology technique in a clinical setting, new
opportunities for evaluation or detection of pathology can be
envisioned. One can monitor the intensity of a liver over time and
pick up more subtle changes, which may occur in such disease states
as cirrhosis, hepatitis, and fatty liver infiltration. This may
lead to improved confidence of changes occurring or not occurring
in lesions during treatment. There is decreased confidence of small
changes with the manual technique, as these changes can be
contributed to operator dependence. One may also be able to pick up
more subtle changes in renal transplants to detect rejection or
acute tubular necrosis at an earlier time point. The technique can
also be used with ultrasound contrast material for improved
quantitation over time to assess treatment response, particularly
the evaluation of neovascularity in a tumor.
One can also envision that more subtle lesions may be
identified. In manual imaging, one optimizes an image to be
recorded while the majority of the scanning is performed without
optimization. With more continuous image optimization, less
conspicuous lesions may be identified during the scanning portions
of the exam.
Conclusions
NTEQ ultrasound technology is a real-time technique that
optimizes ultrasound images throughout the course of an
examination, and, as a result, improves image quality while
significantly reducing the number of buttons that need to be
adjusted during an exam. There are certain situations such as in an
intensive care unit, operating room, or neonatal intensive care
unit, where NTEQ ultrasound technology is extremely helpful in
allowing the operator to be positioned away from the machine and
allowing for optimized images for storage regardless of the ambient
light in the room. If early indications that standardization of
images can be obtained are confirmed, the technique may open up new
uses for ultrasound in the detection and follow-up of pathology.
Further controlled studies are needed to confirm the amount of time
savings, image improvement, ergonomics, and improved consistency of
images using this technique. This technique moves ultrasound one
step closer to being an operator-independent modality.
This publication is sponsored by:
Siemens Medical Solutions USA, Inc.
Ultrasound Division
1230 Shorebird Way
P.O. Box 7393 Mountain View, CA 94039-7393 USA
Siemens Medical Solutions USA
51 Valley Stream Parkway
Malvern, PA 19355-1406
USA Telephone: +1-888-826-9702
www.usa.siemens.com/medical