Manual correction of semi-automatic three-dimensional echocardiography is needed for right ventricular assessment in adults; validation with cardiac magnetic resonance
Manual correction of semi-automatic three- dimensional echocardiography is needed for right ventricular assessment in adults; validation with cardiac magnetic resonance
Ellen Ostenfeld 0 1 3
Marcus Carlsson 1
Kambiz Shahgaldi 2
Anders Roijer 4
Johan Holm 4
0 Department of Cardiology, Malmo, Skane University Hospital , Sweden
1 Department of Clinical Physiology, Lund, Skane University Hospital , Sweden
2 Department of Cardiology, Karolinska University Hospital, Huddinge , Stockholm , Sweden
3 Department of Cardiology, Malmo, Skane University Hospital , Sweden
4 Department of Cardiology, Lund, Skane University Hospital, Sweden; Lund University , Sweden
Background: Three-dimensional echocardiography (3DE) and semi-automatic right ventricular delineation has been proposed as an appropriate method for right ventricle (RV) evaluation. We aimed to examine how manual correction of semi-automatic delineation influences the accuracy of 3DE for RV volumes and function in a clinical adult setting using cardiac magnetic resonance (CMR) as the reference method. We also examined the feasibility of RV visualization with 3DE. Methods: 62 non-selected patients were examined with 3DE (Sonos 7500 and iE33) and with CMR (1.5T). Endocardial RV contours of 3DE-images were semi-automatically assessed and manually corrected in all patients. End-diastolic (EDV), end-systolic (ESV) volumes, stroke volume (SV) and ejection fraction (EF) were computed. Results: 53 patients (85%) had 3DE-images feasible for examination. Correlation coefficients and Bland Altman biases between 3DE with manual correction and CMR were r = 0.78, -22 27 mL for EDV, r = 0.83, -7 16 mL for ESV, r = 0.60, -12 18 mL for SV and r = 0.60, -2 8% for EF (p < 0.001 for all r-values). Without manual correction r-values were 0.77, 0.77, 0.70 and 0.49 for EDV, ESV, SV and EF, respectively (p < 0.001 for all r-values) and biases were larger for EDV, SV and EF (-32 26 mL, -21 15 mL and - 6 9%, p 0.01 for all) compared to manual correction. Conclusion: Manual correction of the 3DE semi-automatic RV delineation decreases the bias and is needed for acceptable clinical accuracy. 3DE is highly feasible for visualizing the RV in an adult clinical setting.
adult; clinical; three-dimensional echocardiography; magnetic resonance; right ventricle; volumes; function
Assessment of the right ventricular volumes and
function is of great importance in the diagnosis of various
heart diseases e.g. pulmonary hypertension and
congenital heart disease [1-3], for the choice of therapeutical
strategies  and not least of prognostic value [5-7].
Two-dimensional echocardiography (2DE) is the most
commonly used clinical imaging modality in the
evaluation of the right ventricle (RV). The complex
geometrical structure of the RV with both a crescent shape and
an outspread inflow and outflow tract requires a
combination of several different scan planes for estimation of
size and function with 2DE. M-Mode and tissue
Doppler imaging of the free lateral wall of the RV are
measurements in one point and are used as surrogates for
the RV function. Hence, current echocardiographic
techniques are not suitable for calculating right
ventricular volumes and function accurately with a simple
Cardiac magnetic resonance imaging (CMR) is
currently the gold standard for quantification and
monitoring volumes and function of the RV. However CMR is
not available at all centres, the equipment is expensive
and bedside acquisition is not possible. Some patients
cannot undergo CMR because of claustrophobia or
implants such as pacemakers and implantable
defibrillators (ICD), even if some implanted cardiac devices is
becoming a relative contraindication for CMR [8,9].
Three-dimensional echocardiography (3DE) potentially
offers a full volume assessment of the RV overcoming
the complex geometry problem. Various algorithms
have been applied to assess the RV with 3DE, such as
multiple planes around the same centreline [10-13], and
parallel multislicing [14-17] leaving room for
interpolation among planes and slices. Recent studies have used
a new tool for RV volume rendering with a
semi-automatic dedicated algorithm. The main focus has been
patients with congenital heart disease [18-20] and young
healthy adult populations [21,22]. Adult patients with
acquired heart disease were recently evaluated with the
semi-automatic dedicated 3DE algorithm [23,24]. Some
investigators have manually corrected the
semi-automatic delineation in all patients , some not at all
 and some if considered necessary . Thus, it is
not clear if manual correction is needed for clinical use
Therefore, our study was designed to assess how
manual correction of the semi-automatic delineation with
3DE influences the accuracy of RV volumetric and
functional measurements compared to CMR in a clinical
setting with a wide range of adult patients. We also
examined the feasibility of visualizing the RV.
Materials and methods
Study population and design
62 non-selected patients referred to a clinically indicated
transthoracic echocardiography (2DE) or CMR were
included. The patients with clinically indicated
echocardiography were examined with an additional research
related CMR, and patients with clinically indicated CMR
were examined with an extra echocardiographic
examination. The clinical CMR had complementary indication
to a formerly performed echocardiography; e. g. RV
volumes and function in suspected arrhythmogenic right
ventricular cardiomyopathy, quantification of
regurgitations in the aortic or pulmonary valves or definition of
infarction size or viability of the myocardium. All
patients underwent 2DE in concordance to ASE
recommendations , three-dimensional echocardiography
(3DE) and CMR. 3DE data was recorded directly in
continuity to the 2DE examination. Patients were examined
with 3DE and CMR with an average of 2 4 days apart
and thirty eight patients within the same day. Exclusion
criteria was standard contraindication to CMR including
claustrophobia (n = 1).
The study was approved by the local ethics committee.
All patients gave written informed consent.
Data acquisition: 3DE with full volume and harmonic
imaging was recorded over 4-7 heart cycles with a matrix
array transducer. All recordings were ECG-gated and
performed with a breath-hold technique. The first 29
patients were recorded with an x4 transducer and Sonos
7500 (Sonos 7500, Philips Healthcare, Andover, Mass.,
USA) and the following 33 patients with an x3-1
transducer and iE33 imaging system (Philips Healthcare). The
apical view was used for recording, though with a more
off-axis approach to be able to include the entire RV.
Depth, sector size, angel and focus were adjusted to focus
the region of interest to the RV. Two to four recordings
were acquired of the RV. The data sets were saved
through a digital format to a workstation connected to a
TomTec server (TomTec Imaging Systems,
Unterschleissheim, Germany) for further analyses.
Data analysis: RV data were interpreted with dedicated
software 4D RV-Function (TomTec Imaging Systems).
Before tracing, end-systole and end-diastole were defined
as the smallest and largest cavity, respectively. The
endocardium was traced manually in end-systole and
end-diastole in the 4-chamber, short-axis and coronal views. The
software algorithm then computed semi-automatic
endocardial border detection over the whole heart cycle.
Thereafter manual correction was done to optimize the
endocardial border delineation in all patients (Figure 1).
The manually corrected and uncorrected (Figure 1)
semi-automatic measurements were noted and evaluated
for difference in accuracy.
The quality of imaging was judged on a 4-graded scale
(1: not visualized, 2: fair, 3: good and 4: excellent)
depending on visible endocardium. Acquisitions where
one of the four to seven sub volumes were dislocated in
the merged full volume data set (also called stitching
artefacts) were not used for measurements.
Cardiac magnetic resonance
A 1.5 T magnetic resonance imaging scanner (Philips
Intera, Philips Healthcare, Andover, Mass., USA) with a
cardiac synergy coil was used to acquire cine images in
the short-axis, long axis 4-chamber and transversal
planes during end-expiratory apnoea and ECG-gating.
Parallel short-axis images were acquired covering the
whole heart from the atria to the apex as well as parallel
transversal images covering the whole heart from the
diaphragm and up to the great vessels. Typical image
parameters were: slice thickness of 8 mm, slice gap of 0
mm, pixel size 1.5 1.5 mm, repetition time 2.8 ms,
echo time 1.4 ms and flip angle 60.
All images were evaluated using freely available off-line
analysis software (Segment 1.8 R1275, http://segment.
Figure 1 Semi-automatic tracing of the right ventricle without and with manual correction. Semi-automatic tracing of the right ventricle
in end-diastole with the RV function analysis program showing the endocardial contour detection without (left image) and with (right image)
manual correction. In both images: Upper right image is the 4 chamber view; lower right image is the coronal view with the apex downwards,
the tricuspid valve to the upper left and the pulmonary valve to the upper right in the image; the three left images are the short-axis views in
three different levels; whereas the upper image here is closer to the base and the lower image closer to the apex. The levels of short-axis are
changeable and the semi-automatic endocardial rendering is manually corrected in all images and in multiple levels. The uncorrected
semiautomatic delineation is less pliable in the anterior and basal part of the RV.
heiberg.se) . End-systole and end-diastole were
defined as with 3DE. Endocardial contours were traced
manually in end-systole and in end-diastole in both
transversal and in short axis planes using established
methods [27-29]. Planimetry of each of the imaging
planes were superimposed to the other (Figure 2), as
well as to the long axis 4 chamber to ensure the
definition of the RV against encountering structures such as
the right atrium, the myocardium, the aorta and the
pulmonary artery. The end-systolic (ESV) and end-diastolic
(EDV) volumes were computed. The mean values of the
two imaging planes (short axis and transversal) were
used for comparison with 3DE.
Endocardial tracings of the two imaging modalities were
performed blinded to prevent influence on the analyses.
Data was analysed with Microsoft Office Excel 2003
and SPSS version 19.0 (SPSS Inc, Chicago, IL, USA). All
results are expressed as a mean SD. Linear regression
analysis with Pearson correlation coefficient and bias
according to Bland-Altman  were used to compare
3DE and CMR measurements. Students paired t-test
was used to investigate statistical differences between
modalities and independent t-test for statistical
differences in measurements between grades of image quality.
The 2-sided probability value of P < 0.05 was considered
to be significant.
We included 62 patients (22 women, 40 men; ages 55
16). Patient characteristics are presented in table 1.
Twenty one patients had impaired right ventricular
function in the meaning of ejection fraction below fifty percent.
Of those were three under investigation for
arrhythmogenic right ventricular cardiomyopathy. The others had
impaired right ventricular function due to left-sided
diseases, such as mainly congestive heart failure and/or
ischemic heart disease (sixteen patients). One patient had
hypertrophic cardiomyopathy and one patient had
aortopathy with significant aortic regurgitation.
Fifty three of the patients (85%) were feasible for
evaluation with 3DE and were used for calculations; of
those, 5 had excellent acoustic window, 22 good
visualisation, and 26 fair acoustic windows.
Figure 2 Cardiac magnetic resonance of the right ventricle. Manual planimetry of the endocardial contour (full lines) is shown of the right
ventricle in cine images. Dots show the traced contours from the corresponding planimetry of short-axis and transversal planes, respectively. The
top images are end-diastole and the bottom images are end-systole. To the left are shown the short axis plane and to the right the transversal
Comparisons with CMR
The correlation coefficient (r) of the manually corrected
3DE compared to CMR was 0.78 for EDV, 0.83 for ESV,
0.60 for stroke volume (SV) and 0.60 for ejection
fraction (EF) with p-values < 0.001 for all (Figure 3+4).
Corrected 3DE consequently underestimated the
volumes with mean values of 127 41 ml for EDV, 64
28 ml for ESV and 63 20 ml for SV, with p-values
0.001 for all (Table 2). EF on the other hand was not
significantly different (p = 0.08). Biases was for EDV -22
Table 1 Patient characteristics
n = 62
Data expressed as mean SD (range) or as percentages. Indication for
examination is noted. Some patients had more than one indication for
27 mL (-15 18% of the mean CMR-derived EDV
value), for ESV -7 16 mL (-10 21% of the mean
ESV value), for SV - 12 18 mL (-15 26% of the
mean SV value) and for EF -2 8% (-3 16% of the
mean EF value) (Figure 3+4).
The uncorrected semi-automatic 3DE had r-values of
0.77 for EDV, 0.77 for ESV, 0.70 for SV and 0.49 for EF
compared to CMR (p < 0.001 for all) (Figure 5+6). The
uncorrected analysis underestimated the volumes as well
as function with mean values of 117 mL 38 mL for
EDV, 64 24 mL for ESV, 53 19 mL for SV and 46
9% for EF with p-values 0.001 for all, when compared
to CMR. The biases for uncorrected EDV, SV and EF
were larger compared to the manually corrected
assessment (EDV -32 26 mL, SV -21 15 mL and EF -6
9%; p 0.001 for all) and for uncorrected ESV there
was no difference in bias (-8 17 mL; p = 0.7) (Table
When excluding patients with fair acoustic window
(grade 2), there was no change in correlation between
corrected 3DE and CMR (EDV, ESV, SV and EF
computing r values of 0.78, 0.89, 0.63 and 0.67 with p-values
< 0.001 for all), and there were no significant differences
in mean values or biases of excellently and well
visualized (grade 4 and 3) compared to those fairly visualized
(p = 0.34 for EDV, p = 0.99 for ESV, p = 0.09 for SV
and p = 0.17 for EF) (table 2). When comparing
uncorrected 3DE, without fairly visualized patients, to CMR
the r-values were 0.76, 0.84, 0.78 and 0.60 for EDV,
ESV, SV and EF, respectively (p < 0.001 for all) and had
no difference in means and biases compared to those
fairly visualized (p-values of 0.45 for EDV, 0.58 for ESV,
0.43 for SV and 0.72 for EF) (table 2).
Figure 3 Regression and Bland-Altman analyses of right ventricular end-diastolic and end-systolic volume with manual correction. To
the left is shown the linear regression analysis of right ventricular end-diastolic volume (EDV) and end-systolic volume (ESV) using 3-dimensional
echocardiography (3DE) images against cardiac magnetic resonance (CMR), when manually correcting the semi-automatic delineation. Dashed
line shows the linear regression line and full line the identity line. To the right is shown the Bland-Altman plot for EDV and ESV. The full lines
show bias and the dashed lines are the limits of agreement (LOA) of 1.96 standard deviation (SD).
All patients were manually corrected in the
semi-automatic delineations. The extent of the manual correction,
described by the relative difference between the
manually corrected and semi-automatic delineation, had a
mean of 10 19% for EDV (range -28 to 77%), 0 17%
for ESV (range -35 to 40%), 23 38% for SV (range -26
to 206%) and 11 18% for EF (range -24 to 74%). The
smallest relative difference was 0% for EDV, 0% for ESV,
-1% for SV and 1% for EF.
The manually corrected 3DE analysis was more time
consuming 1337 407 than uncorrected 3DE
analysis 344 136 (p < 0.001) and CMR transversally
1134 535 (p < 0.05) but not CMR short-axis 1211
509 (p = 0.05).
This study has shown that manual correction of the
semi-automated 3DE of the RV is needed as the bias
increases without manual correction. We found
underestimation of end-diastolic, end-systolic and stroke
volume, but not ejection fraction using CMR as a
3DE was feasible for imaging of the RV in a large
proportion (85%) of adult patient with unselected
The 3DE RV volumes were underestimated compared
to CMR in our study. The underestimation of the
corrected EDV and SV were balanced and therefore EF
does not differentiate between the methods (Table 2).
The underestimation of volumes is similar to prior
studies using semi-automatic dedicated software [14,18,23].
The underestimation of volumes was mainly caused by
insufficient coverage of the right ventricular outflow
tract (RVOT) and the anterior wall of the RV on 3DE.
This occurred despite the attempt to include and put
focus on the outflow tract with a lateralized, tilted and
rotated image acquisition and to have the tricuspid, the
pulmonary valve and the apex in the same scan plane,
(Figure 7). In some patients this lateral approach could
not be used because of shadowing from lung tissue or
costae and therefore image acquisition was moved
medially. With the medial approach the pulmonary valve was
not in the same scan plan as the tricuspid valve and the
RV apex and this cause uncertainty whether the whole
Figure 4 Regression and Bland-Altman analyses of right ventricular stroke volume and ejection fraction with manual correction. To the
left is shown the linear regression analysis of right ventricular stroke volume (SV) and ejection fraction (EF) using 3-dimensional
echocardiography (3DE) images against cardiac magnetic resonance (CMR), when manually correcting the semi-automatic delineation. Dashed
line shows the linear regression line and full line the identity line. To the right is shown the Bland-Altman plot for SV and EF. The full lines show
bias and the dashed lines are the limits of agreement (LOA) of 1.96 standard deviation (SD).
RVOT was included in the acquisition. Furthermore, the
medial approach also cause difficulties to visualize the
RVOT because of shadowing from the proximity to the
sternum . Insufficient visualization of the RVOT is a
known problem from an earlier 3DE study by Anwar et
al who found inadequate RVOT coverage in 48% of
patients although this was the region of interest for
Obesity can cause ultrasonic penetrance problems
with substantial amount of tissue in front of the heart
and in our patient population several patients were
obese (BMI ranged from 17-35). On the other hand the
Results of mean values and biases of cardiac magnet resonance imaging (CMR), manually corrected semi-automatic and uncorrected semi-automatic
threedimensional echocardiography (3DE) analysis. Means expressed with standard deviation (SD). 3DE image quality: 2 means fairly visualized, 3 good and 4
excellent visualized. n = 53 for 2+3+4 and n = 27 for 3+4.
: compared to CMR, p 0.001; : compared to corrected 3DE, p 0.001; No significant differences in means and biases between image quality more than 2
compared to less than 3.
Figure 5 Regression and Bland-Altman analyses of right ventricular end-diastolic and end-systolic volumes without manual correction.
Results show linear regression analysis and Bland-Altman analysis of right ventricular end-diastolic and end-systolic volumes without manual
correction of the semi-automatic volume delineation. Explanations as in figure 3.
underweighed patients can make it difficult to get
sufficient probe-skin contact in between the ribs.
The RV is highly trabeculated and sometimes has a
prominent moderator band, crest and papillary muscles
which make it more difficult to differ from the correct
endocardial border with 3DE. These problems also have
to be dealt with when reading CMR images. In addition,
the anterior papillary muscle or the moderator band can
be mistaken for the anterior wall in the short axis image
planes with the semi-automatic 3DE; especially, if a
lower image quality of the anterior wall and RVOT is
present. This was a frequent problem for the
semi-automatic delineation in our study.
Trabeculation and papillary muscles were included in
the volumes in our study. Mor-Avi et al showed the
spatial resolution influences the detection of trabeculation
in the left ventricle and recommended as well to include
the trabeculae in the cavity when examining the left
ventricle with 3DE .
We used disc summation for CMR volume
calculations and a RV dedicated algorithm for 3DE volume
calculations. Our biases could to some extent be explained
by differences in the two methods analysis algorithms
and might even be explained in the dissimilarities of the
imaging acquisition techniques. These differences have
been proposed as a reason to the underestimation of
3DE volumes in earlier studies between CMR and 3DE
[13,23]. Differences in volumes and not in function are
also seen in other studies of other images modalities of
the heart e g gated myocardial perfusion SPECT
compared to CMR, suggesting that there are inter-modality
differences in the calculation of volumes .
Five percent of the patients had atrial fibrillation or
atrial flutter. Stitching artefacts can occur when
combining four to seven sub volumes with very different
RRintervals, hence end-systole and end-diastole in different
time frames. In patients with atrial fibrillation/flutter,
four-beat ECG gated acquisition seems to have lower
left ventricular volumes and EF than single-beat
acquisition . It has been suggested that stitching artefacts
could be one explanation. In our material all atrial
fibrillation/flutter patients were well regulated and had stable
heart frequency and therefore there were no stitching
The coronal plane in the semi-automatic software was
slightly adjustable and had a large open angle to the
4Figure 6 Regression and Bland-Altman analyses of right ventricular stroke volume and ejection fraction without manual correction.
Results show linear regression analysis and Bland-Altman analysis of right ventricular stroke volume and ejection fraction without manual
correction of the semi-automatic delineation. Explanations as in figure 4.
Figure 7 Image difficulties with 3DE of the right ventricle. The right ventricle (RV) is depicted with the adjacent structures of the right
atrium (RA), the pulmonary trunk (PA), the sternum (S), the ascending aorta (Ao) and lung tissue. A: shows how the sternum or lung tissue can
shadow the imaging of the RV especially the anterior part of the right ventricular outflow tract (RVOT). B: shows how the anterior part of the RV
might not be included in the whole volume when trying to avoid this shadowing.
chamber long-axis plane. In this blind angel was e g
the anterior, anterolateral and lateral part of the RV and
RVOT. This leaves the area hardest to visualize without
a long-axis plane to trace or correct in (Figure 1). To be
able to trace in a third long-axis plane intersected in
and in between the other two long-axis planes could
have facilitated the semi-automatic delineation and
might have avoided the more time consuming manual
correction in several short-axis levels.
In CMR we used both short-axis and transversal
orientations, since there can be difficulties to distinguish
the RV boundaries at the level of the tricuspid valve and
the outflow tract; especially if there is no perpendicular
plane to correct in [15,36]. To minimize this limitation
we superimposed the tracing from both orientations to
each other with the help of the software as shown in
Figure 2. The mean values were used for calculations,
since there is a systematic difference in short-axis
volumes compared to the volumes of a transversal
orientation in the acquisition of images .
The 3DE frame rate was in average 20 6 frames per
cardiac cycle. If both the volume and the heart rate are
low, there is a risk that the true end-diastole and
endsystole are missed between frames and that could yield
differences in 3DE volumes compared to CMR.
Some of the differences could also be explained by the
fact that two different 3DE transducers were used in the
echocardiographic examinations. Newer and smaller
transducers have higher temporal and spatial resolution
and that might improve the visualization of the RV in
Fifteen percent of the patients were not feasible for
interpretation and poor acoustic window remains to be
a major limitation to 3DE as well as to 2DE. Contrast
enhancement has been shown to improve 3DE
volumetric quantification of the left ventricle and may also
improve RV examination with 3DE .
Manual correction of the 3DE semi-automatic
delineation of the RV is needed as the biases increase without
manual correction when compared to CMR as a
reference. We found underestimation of end-diastolic,
endsystolic and stroke volume, but not ejection fraction, for
the corrected delineation. 3DE is feasible in an
unselected adult patient material for visualizing the right
ventricle. 3DE may be a useful clinical tool for RV
evaluation in the future with considerable better volume
accuracy than 2DE, but still not in parity with CMR
2DE: 2-dimensional echocardiography; 3DE: 3-dimensional echocardiography;
CMR: Cardiac magnetic resonance; EDV: End-diastolic volume; EF: Ejection
Fraction; ESV: End-systolic volume; RV: Right ventricle; RVOT: Right ventricular
outflow tract; SV: Stroke volume.
EO contributed to the study design, fund raising, inclusion of patients,
echocardiographic image acquisition, analysis and interpretation of data and
writing the manuscript. MC contributed with study design, fund raising, CMR
coordination and image acquisition and drafted the manuscript. KS helped
with inclusion of patients, echocardiographic image acquisition, image
coordination and manuscript revision. AR contributed with
echocardiographic coordination and image acquisition and manuscript
revision. JH contributed to the study design and drafted the manuscript. All
authors read and approved the final manuscript.
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