Advantages of Volume NT™

Article #
WP201012-VNT
Issue Date 10-December-2010
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The Clinical Usefulness of Volume NT™ Using
Three-dimensional (3D) Ultrasound (US)
Hye-Sung Won, M.D.*, Min-Kyung Hyun, M.D.*, Hyangsuk Lee, RDMS*
Department of Obstetrics and Gynecology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea
INTRODUCTION & OBJECTIVES
Nuchal translucency (NT) is a highly sensitive screening tool for both fetal aneuploidy and congenital
structural anomalies including congenital heart defects; it is gaining in popularity and acceptance among both
patients and clinicians.¹ In combination with maternal serum, PAPP-A and free beta-hCG, increased NT have
been demonstrated to provide efficient Down’s syndrome risk assessment, with a detection rate of 80-87%
(5% false-positive rate), and it also allows earlier diagnosis of fetal aneuploidy.²­ˉ³
A correct NT measurement is determined by the quality of the image, the magnification, the angle of
insonation, the B-mode image (gray scale) settings, and proper placement of the calipers.4 Simple errors in
measurement may have a significant effect on risk assessment. Therefore, to preserve the high efficacy of NT
as a risk assessment tool, the ability and accuracy of operators in order to acquire a reliable measurement of
NT is important.5
In this study, we used three-dimensional (3D) ultrasound (US) for the detection of the mid-sagittal section.
The purposes of this study are to evaluate the clinical usefulness of semi-automated measurement of NT
using 3D US and to investigate whether the clinical experience of the operators has an effect on the accuracy
of the measurement of NT.
METHODS
Between July and November 2010, ultrasound examination was performed on 107 pregnant patients at
11-13+6 weeks’ gestation. Two experienced operators participated in this study. Each operator manually
measured the nuchal translucency and also automatically using Volume NT™ software. One inexperienced
operator then examined 10 of the pregnant patients. Each operator was blinded to any pre-existing
measurements, all of which had been acquired trans-abdominally using an Accuvix V20 Prestige v2.03 with
the V4-8 probe (Samsung Medison Co., Ltd, Seoul, Korea).
1
operator. Manual measurement of the NT was
performed according to the FMF guidelines.
Automatic measurement of the NT with Volume
NT™ from on to on of the two echogenic lines
2D-H-mean - 3D-H-mean
The identical protocol was performed by each
delineating the nuchal translucency, is
In an approximated, mid-sagittal section determined
by conventional B-mode ultrasound, the operator
A. Volume Scanning in the 3D Mode
pressed on the Volume NT button, after which the
3D volume data was obtained by a sweep of the
transducer. When the most representative midsagittal section appeared, the operator placed the
2D-NH-mean - 3D-NH-mean
demonstrated in Figure 1.
Figure 2. Pearson's correlation coefficient test of 2D maximal value
and 3D maximal value
RESULTS
ROI box in the nuchal area and the scanner
(p < .001); for the max 2D and 3D non-harmonic
caliper was then placed automatically on the inner
border of the lower echogenic line (on to on
measurement).
The nuchal translucency was measured using 2D
2D-NH-mean - 3D-NH-mean
3D harmonic measurements was 0.847
upper caliper was then placed automatically on the
inner border of the upper echogenic line. The lower
B. Seed Point for the Mid-sagittal View;
Set a seed point in Diencephalon / Thalamus
1. The correlation coefficient for the max 2D and
automatically selected the best measurement. The
measurements it was 0.887 (p < .001) (Fig. 2).
2. The nuchal translucency using threedimensional ultrasound was significantly greater
than that using two-dimensional ultrasound
(Table 1).
harmonic, 2D non-harmonic, 3D harmonic, and 3D
3. The intra-operator repeatability was assessed
non-harmonic US. Three attempts were made to
using intraclass correlation coefficients (ICC)
obtain each nuchal translucency measurement (for
mean and maximum of both the two- and threedimensional measurements were then compared.
The intraclass correlation coefficient (ICC) was
used to assess the reliability and repeatability.
varying from 0.941 to 0.967 for the experienced
2D-NH-Max - 3D-NH-Max
a total of twelve measurements per patient). The
operators (Table 2).
4. The inter-operator difference in nuchal
translucency for the experienced operator and
the inexperienced operator was significant using
two-dimensional ultrasound (0.072 ± 0.081 vs.
C. Automatic NT Measurement;
Set an ROI box in the NT area
The NT value is the maximum value in of the ROI
0.131 ± 0.065, p = 0.022), unlike that using threeFigure 3. Bland and Altman scatter diagrams showing the intraoperator difference in the means and the max between the 2D
and 3D NT values (in mm).
Figure 1. Automatic NT measurement using Volume NT™
2
dimensional ultrasound (0.191 ± 0.106 vs.
0.166 ± 0.071, p =1.0) (Table 3).
3
CONCLUSION
Table 1. Comparison of the value of 2D and 3D measurement by
experienced operators
Mean ± 2SD
(mm)
Variable
In this study, the results of the measurements were
Mean Difference
p - value
(mm)
Harmonic Mean
2D
3D
1.24 ± 0.84
1.31 ± 0.81
0.073
.003
Harmonic Max
2D
3D
1.36 ± 0.91
1.44 ± 0.87
0.095
.002
Non-harmonic
Mean
2D
3D
1.28 ± 0.85
1.29 ± 0.61
0.076
<.001
Non-harmonic
Max
2D
3D
1.40 ± 0.89
1.40 ± 0.64
0.077
.003
highly correlated. However, a significant difference in
the means and the max between the 2D and 3D
results was observed. This suggests that the Volume
NT™ provides a more accurate, mid-sagittal section
and detects the deepest pocket of NT.
The intra- and inter-operator reproducibility of
Volume NT™ is high. Therefore, automation of the
nuchal translucency measurement may substantially
reduce the within and between operator variation in
the measurement of NT achieved using the
Table 2. Intra-operator repeatability with experienced operators;
Intraclass Correlation Coefficient (ICC)
traditional, manual approach. In particular, it may be
useful for inexperienced operators in order to
Variable
N
ICC
2D Harmonic
107
0.963
2D Non-Harmonic
107
0.967
3D Harmonic
107
0.959
3D Non-Harmonic
107
0.941
improve the intra- and inter-operator reliability.
REFERENCES
1. Sheppard C, Platt LD. Nuchal translucency and first
trimester risk assessment: a systematic review.
Ultrasound Q. 2007;23(2):107-16.
2. Malone FD, Canick JA, Ball RH, Nyberg DA,
Comstock CH, Bukowski R, et al. First-trimester or
second-trimester screening, or both, for Down's
syndrome. N Engl J Med. 2005;353(19):2001-11.
Table 3. Difference of 2D and 3D NT measurement by operators
with different levels of related clinical experience
Variable
Experienced
Inexperienced
p - value
2D (mm)
0.131 ± 0.065
0.072 ± 0.081
.022
3. Wald NJ, Rodeck C, Hackshaw AK, Walters J, Chitty
L, Mackinson AM. First and second trimester antenatal
screening for Down's syndrome: the results of the
Serum, Urine and Ultrasound Screening Study
(SURUSS). J Med Screen. 2003;10(2):56-104.
4. Abuhamad A. Technical aspects of nuchal
3D (mm)
0.166 ± 0.071
0.191 ± 0.106
translucency measurement. Semin Perinatol.
2005;29(6):376-9.
1.0
5. Evans MI, Van Decruyes H, Nicolaides KH. Nuchal
translucency measurements for first-trimester
screening: the ‘price’ of inaccuracy. Fetal Diagn Ther.
2007;22(6):401-4.
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