Download Min-dose双源CT技术与三维超声心动图在主动脉瓣狭窄中的对比研究

Comparison of low-dose sequence of dual-source CT and echocardiography for preoperative
evaluation of aortic valve disease
FENG Juan, WANG Xi-ming, JI Xiao-peng, LI Hai-ou, LI Qiao, GUO Wen-bin and WANG Zheng-jun
Department of Ultrasound, Shandong Provincial Hospital, Shandong University, Jinan,
China (Feng J, Li Q and Guo WB)
Shandong Provincial Key Laboratory of Diagnosis and Treatment of Cardio-cerebral
Shandong Medical Imaging Research Institute, Jinan, Shandong 250021, China (Wang
HO)
Department of Cardiovascular Surgery, Shandong Provincial Hospital, Shandong
Shandong 250021, China (Wang ZJ)
Shandong 250021,
Vascular Diseases,
XM, Ji XP and Li
University, Jinan,
Keywords: radiation dose; coronary CT angiography; dual-source CT; cardiac function; aortic valve
annulus diameters
Abstract
Background Accurate evaluation of coronary artery, aortic valve annulus diameter (AVAD) and cardiac
function in patients with aortic valve disease is of great significance for surgical strategy. In this study we
explored the preoperative evaluation of low-dose sequence (MinDose sequence) scan of dual-source CT
(DSCT) for those patients.
Methods Forty patients suspected for aortic valve disease (experimental group) underwent MinDose
sequence of DSCT to observe coronary artery, aortic valve annulus diameters (AVAD) and left ventricular
ejection fraction (LVEF). Another 33 subjects suspected for coronary artery disease (control group)
underwent conventional retrospective ECG-gated sequence of DSCT. Two-dimensional transthoracic
echocardiography (2D-TTE) and four-dimensional transthoracic echocardiography (4D-TTE) were applied in
the experimental group to measure AVAD and LVEF and compared with MinDose-DSCT.
Results There was a strong correlation between LVEF measured by 2D-TTE and MinDose-DSCT (r=0.87,
P<0.01), as well as between 4D-TTE and MinDose-DSCT (r=0.90, P<0.01). AVAD measured by
MinDose-DSCT was in good agreement with corresponding measurements by 2D-TTE (r=0.90, P<0.01).
The effective dose in the experimental group was 63.54% lower than that in the control group.
Conclusions MinDose sequence of DSCT with a low radiation dose serving as a one-stop preoperative
evaluation makes effective assessment of the coronary artery, AVAD and LVEF for patients with aortic valve
disease.
Aortic valve disease, especially calcific aortic stenosis, is the most common elderly valvular heart disease
that is secondary to coronary artery disease and arterial systemic hypertension in Western countries.1 With a
rapid aging population, heart disease incidence caused by aortic stenosis and insufficiency due to aortic valve
degeneration is rising year by year. In recent years the valvular stenosis caused by the degenerative disease of
the aortic valve has gradually replaced rheumatic heart disease and become the major cause of aortic valve
replacement in older people.
2-8
Aortic valve replacement is an effective cure for these diseases, and
preoperative evaluation including coronary tree, cardiac function and aortic valve annulus diameters (AVAD)
is essential for the surgical strategy, especially for determining whether coronary artery bypass is needed and
how to choose the valve model.
Echocardiography including M-mode, 2D, Doppler techniques and especially newly 4D plays a pivotal role
in the diagnosis and follow-up of aortic valve disease.
2, 9
The echocardiographic examination aims at not
only assessing the aortic valve (morphology, calcification, motion and hemodynamics), but also evaluating
LV geometry, function and coexistence of cardiovascular disease (e.g. aortic root disease, other valvular
abnormalities, pulmonary arterial hypertension). However, it is difficult for echocardiography to display
coronary tree and multiple dimensional facets of aortic valve clearly. Although the 4D ultrasound has been
used in clinical diagnosis for several years,
10-12
it still cannot overcome the shortcomings above because it
is based on 2D images.
Coronary angiography (CAG) is imperative if heart surgeons highly suspect patients suffering from coronary
heart disease (CAD). For those suspected CAD patients, undoubtedly DSCT would be chosen as the
preferred method of examination in order to explore the details of coronary artery because of its non-invasion
and less cost.
13, 14
CT angiography can also display the abnormality of aortic valve. 15, 16 On the other hand,
careful selection of CT scanning protocols is needed to keep the radiation exposure “as low as reasonably
achievable (ALARA)” on the premise of diagnosable images. The low-dose sequence (MinDose sequence)
we adopted includes: (1) shortening the full exposure dose window and 4% of full exposure dose in all the
other phases of the cardiac cycle; (2) choosing different tube voltage according to the BMI; (3) adjusting tube
current by means of CareDose 4D. After the parameters set as described above we could regulate individual
radiation dose as low as possible.
The purpose of this study was to explore the preoperative evaluation value of MinDose sequence of
dual-source CT (DSCT) for patients with aortic valve disease in the aspects of the effective dose compared
with conventional retrospective ECG-gated sequence of DSCT, LVEF and AVAD compared with
two-dimensional TTE (2D-TTE) and four-dimensional TTE (4D-TTE). 17-21
METHODS
Patients
A total of 48 consecutive patients with aortic valve disease were retrospectively identified as the
experimental group at our institution from March 2012 to January 2013. Inclusion criteria: patients with
aortic valve disease (aortic stenosis and/or aortic insufficiency) diagnosed by 2D-TTE older than 60 years old
suspected CAD. Exclusion criteria: body weight >85Kg, severe arrhythmia, after received 50 or 100 mg
atenolol orally still with heart rate >70 beats per minute (bpm), renal insufficiency (serum cretinine >
1.5mg/dl), known anaphylactic reactions to iodine-containing contrast material, history of coronary stents
and bypass grafts and hemodynamic instability. Eight patients had to be excluded from study participation
(obvious arrhythmia: n=3; tachycardia: n=2; body weight >85Kg: n=3), whereas 40 patients (33 only aortic
stenosis, 4 only aortic insufficiency, 3 aortic stenosis coexisting with moderate to severe valvular
regurgitation; 28 male, 12 female; mean age 61.3±13.6 years, range 42 to 77) were included as the
experimental group. Thirty three subjects initially referred to CT angiography to rule out CAD served as the
control group. All patients in the experimental group underwent both 2D-TTE, 4D-TTE and MinDose-DSCT
performed as part of routine clinical evaluation within a one-week period, with no change in clinical status
between the studies. The study was approved by the local institutional review board and all patients gave
written informed consent.
DSCT protocol and image acquisition
A DSCT scanner (Somatom Definition Flash, Siemens Medical Solutions, Forchheim, Germany) was used to
perform CT coronary angiography. CT parameters were as follows: 2×128×0.6 mm detector collimation,
enabled by Z-Sharp technology and a gantry rotation time of 0.28s. Sublingual nitroglycerin spray (0.4 mg;
Roche Pharma, Eberbach, Germany) was given 3 minutes before examination. Bolus tracking technique was
used with the region of interest placed into the aortic root with a threshold of 100 Hounsfield units (HU). The
scans were performed in cranio-caudal direction from the level of 1cm below the carina to diaphragm during
a breath hold of 8-12 seconds. Mean acquisition time was 3.5-5.5 s. The pitch was 0.18-0.22. A dual-head
power injector (Stellant; Medrad, Indianola, PA) was used. A 60-70 ml bonus of intravenous contrast material
(Schering Ultravist, Iopromide, 350 mg I/ml, Berlin, Germany) followed by 50ml of saline chaser into the
antecubital vein. Body mass index (BMI)-based adjustments of tube voltage were performed: <19 Kg/m2,
tube voltage 80 kV, 19-25 Kg/m2, tube voltage 100 kV, >25 Kg/m2, tube voltage 120 kV,22 and tube current
200-300 mAs per rotation applying dose modulation (CareDose 4D®, Siemens).
11, 12
Full tube current time
window was applied according to HR: as HR ≤60 bpm, time window at 70-80% of the RR interval, as 60-70
bpm, time window at 66-76% of the RR interval; 23 minimal tube current (4%) was used in all other parts of
the cardiac cycle. The control group underwent conventional retrospective ECG-gated acquisition (120 kV,
360 mAs) applying a full tube current between 40-75% of the cardiac cycle and 20% tube current outside the
pulsing window.
Coronary segments were defined according to the scheme of the American Heart Association (AHA).
24, 25
The image quality of the coronary arteries was evaluated on a per-segment basis using interactive oblique
multiplanar reformations by two experienced independent observers in cardiac CT on a 4-point scale:
26
1,
excellent (no artifacts); 2, good (minor artifacts); 3, mediocre (artifacts but still diagnostic); 4, poor (severe
artifacts rendering image quality non-diagnostic). A consensus readout was appended in case of disagreement,
and the consensus results were taken for final data analysis.
DSCT image reconstruction protocol
DSCT images were reconstructed in a monosegment algorithm by using a section thickness of 0.75 mm and
reconstruction interval of 0.5 mm and a medium smooth-tissue convolution kernel (B26f). Images were
reconstructed from 66-76% or 70-80% of the RR interval (depended on different heart rate) in 2% increments,
and the best reconstruction phase was used for evaluation. All images were transferred to an external
workstation (syngoMMWP VE40A, circulation) for further analysis. In addition to the CT axial slices,
multiple planar reformation (MPR), volume rendering (VR), curved planar reconstruction (CPR) and
maximum intensity projection (MIP) were used to visualize cardiac abnormalities. Axial cuts through the
aortic root were obtained by aligning the three perpendicular planes (one axial axis and two longitudinal axis:
oblique sagittal and oblique coronal).
15
Images were reconstructed at 70% of RR interval and AVAD were
measured by using double oblique reconstruction.
16
The aortic annulus is defined as the circumferential
connection of the aortic leaflets’ most basal attachments in the reconstructed axial plane (see Fig, 1). The
AVAD was also intra-operatively (AVAD-intra) measured by the surgeons who were blind to the study using
the bioprosthetic heart valve sizers set (St. Jude Medical, St. Paul, MN). Left ventricular end-diastolic
volume (LVEDV), end-systolic volume (LVESV) and LVEF were calculated by the software. The
end-diastolic phases typically were defaulted automatically and end-systolic phases were set at the 40% of
the RR interval. Manual correction was made whenever needed.
Fig 1. Example of a 57-year-old male aortic stenosis patient (100kV, 220mAs, DLP 165mGy·cm, ED 2.310mSv). Images
show aortic annulus (arrows) in oblique-sagittal (a) and oblique-coronal (b) plane
Estimation of radiation dose
The volume CT dose index (CTDIvol) and dose length product (DLP) were obtained from the information
generated by the CT system. Effective radiation dose (ED) was calculated by the DLP multiplied by the
conversion coefficient for the chest: ED=DLP (mGy·cm) ×0.014(mSv·mGy-1·cm-1). 27, 28
Echocardiography protocol and image acquisition
Echocardiography was performed in the experimental group with a standard protocol on General Electric
Vivid E9 (Milwaukee, WI) cardiac ultrasound systems. With regard to 2D-TTE, the LVEF was calculated
with the modified Simpson’s method. Parasternal long-axis loops of the aortic root were acquired with zoom
mode and the AVAD was measured at the insertion of the leaflets in end diastole. 29, 30 Observation of origin,
proximal morphology and inside diameter of the coronary artery could be achieved from the short axes
section of large arteries. LVEF and AVAD were consensually assessed by two independent, blinded
cardiologists experienced in echocardiography. 4D-TTE was used to measure LVEF directly according to 3D
reformation.
Reproducibility studies
Average of three measurements was taken for all measured values. For each technique, measurement of
LVEF and AVAD was performed by two experienced observers and each blinded to the other’s results.
Statistical Analysis
Data are summarized as mean ± standard deviation(x ±SD). Correlations between two variables were
assessed by Pearson correlation coefficients. The AVAD measured by surgeons and by DSCT were compared
using paired Student’s T-test. Valid coronary segments for diagnosis were evaluated with 2 test. Agreement
and bias among modalities was assessed using Bland-Altman analysis. Reproducibility was assessed by the
interclass correlation coefficient (ICC) and coefficient of variation (CV). A P value <0.05 was considered to
be significant. Analysis was performed using SPSS software, version 19.0 (IBM Corporation, NY, USA).
RESULTS
Patient characteristics
The patients in the experimental group completed MinDose sequence of DSCT as well as echocardiographic
studies, while the patients in the control group completed the conventional retrospective ECG-gated
acquisition. Mean heart rate during CT coronary angiography was 56.3±11.4 bpm (range 44-70 bpm). Except
median heart rate was present a significant difference (P<0.01) (56.3±11.4 bpm vs 70.2±14.6 bpm), there was
no significant difference between the experimental group and the control group in mean gender, body weight,
BMI, and scan length.
Image quality
All patients acquired satisfactory image quality. The mean score of imaging quality of MinDose sequence
was 1.8±0.2, not significantly different from that of control group 1.6±0.3 (P>0.05). The proportion of valid
coronary segments for diagnosis were 509/528 (96.40%) and 416/424 (98.11%) respectively in the
experimental group and the control group with no significant difference (2=0.002，P=0.961) (Table 1).The
observation of coronary by 2D-TTE was very limited, the origin of coronary could be clearly shown only in
part of the patients (8/40 cases), the remote status and lumen of blood vessel could not be displayed.
Although during systolic cardiac cycle the tube current was reduced to 4% of the full exposure dose and
inevitably means image noise increased to some extent, but in terms of the whole process for the evaluation
of cardiac function there was a very small impact. In addition to clearly showing coronary, we could easily
complete the reconstruction of the aortic annulus from the oblique-sagittal and the oblique-coronal planes
using double oblique multiplane reformations with the help of cardiac viewer software. Observation of the
valve ring, leaflets, calcification and prolapse through the short-axis image of the aortic root had significant
advantages compared to echocardiography (see Fig. 2, 3).
Table 1. Coronary image quality score results
Croups
patients
Control
Coronary
score
1
2
3
4
Segments
(n)
Numbers
(n)
Proportion
(%)
Numbers
(n)
Proportion
(%)
Numbers
(n)
Proportion
(%)
Numbers
(n)
Proportion
(%)
528
424
180
182
34.09
42.92
302
219
57.20
51.65
27
15
5.11
3.43
19
8
3.60
1.83
Fig 2. Example of a 61-year-old female aortic insufficiency patient (100kV, 300mAs, DLP 218mGy·cm, ED 3.052mSv). A
short-axis image clearly shows the aortic right coronary valve prolapse in different phases (a and b)
Fig 3. Example of a 52-year-old male patient with bicuspid aortic (100kV, 240mAs, DLP 178mGy·cm, ED 2.492mSv).
The short-axis image clearly shows the morphology and apparent calcification of the valve leaflets.
Data correlation analysis between MinDose-DSCT and TTE
Results are shown in Fig. 4. In the experimental group, there was a strong correlation between LVEF
measured by MinDose-DSCT and 2D-TTE (r=0.87, P<0.01), much stronger correlation between
MinDose-DSCT and 4D-TTE (r=0.90, P<0.01) was regarded too. LVEF on MinDose-DSCT ranged from
21% to 72%, and 22 patients had reduced LVEF (<50%). As compared with 2D-TTE, MinDose-DSCT
overestimated AVAD [(24.2±3.2) mm vs (23.8±2.5) mm, P=0.01] but still was in good agreement with
corresponding measurements by 2D-TTE (r=0.90, P<0.01). There was no significant difference between
AVAD-MinDose-DSCT and AVAD-intra (t=-0.712, P=0.481). The distribution of the points in Fig. 6 (a, b)
shows that the inter-observer variability of LVEF and AVAD measured by MinDose-DSCT was low. Fig. 5
(c-e) also obviously demonstrates closer agreement and low bias for LVEF derived by MinDose-DSCT
compared with 4D-TTE and 2D-TTE, AVAD derived by MinDose-DSCT compared with 2D-TTE.
Fig 4. Linear regression plots demonstrate the agreement of MinDose-DSCT and 2D-TTE (a), MinDose-DSCT and
4D-TTE (b) in the analysis of LVEF; MinDose-DSCT and 2D-TTE (c) in the analysis of AVAD.
Fig 5.
Inter-observer reproducibility of LVEF and AVAD (a, b) (a: LVEF, b: AVAD). Bland-Altman plots demonstrating
closer agreement and lower bias for cardiovascular MinDose-DSCT–4D-TTE derived LVEF (c) compared with
MinDose-DSCT–2D-TTE (d). The distribution of the points also suggesting closer agreement and lower bias for
MinDose-DSCT–2D-TTE derived AVAD (e). The central horizontal line corresponds to the mean of the differences of the
two measurements and the two exterior lines correspond to 2×SD of the differences(c-e).
Reproducibility analysis
In analysis of inter-observer CV and ICC, Table 2 shows that among the LVEF and AVAD variables studied,
MinDose-DSCT provided better performance for the evaluation of data (lower CV and higher ICC).
Especially LVEF provided by 2D-TTE was recorded the poorest CV and ICC (respectively 8.26% and
0.763).
Table 2. Inter-observer variability of LVEF, AVAD measurements by 2D-TTE, 4D-TTE and MinDose-DSCT
CV
2D-TTE
4D-TTE
MinDose-DSCT
ICC
LVEF
AVAD
LVEF
AVAD
8.26%
7.18%
5.92%
7.31%
6.25%
r=0.763, P=0.021
r=0.809, P=0.017
r=0.822, P=0.009
r=0.776, P=0.018
r=0.813, P=0.012
CV, coefficient of variation; ICC, intraclass correlation coefficient; LVEF, left ventricular ejection fraction; AVAD, aortic
valve annulus diameter; 2D-TTE, two-dimensional transthoracic echocardiography; 4D-TTE, four-dimensional transthoracic
echocardiography
Comparison of radiation dose
The radiation dose parameters of two groups were summarized in Table 3.The CTDIvol, DLP as well as ED
of the experimental group differed significantly from those of the control group (P<0.0001). The effective
dose in the experimental group (3.2±0.2 mSv) was 63.54% lower than that in the control group (8.8±3.0
mSv).
Table 3. Radiation dose estimates in the two protocols
MinDose
Standard
dose
t or t’
P
Image
Quality
score
number
Contrast
Agent(ml)
CTDIvol
(mGy)
DLP
(mGy·cm)
ED(mSv)
40
60.1±17.3
14.2±2.5
185.3±14.6
3.2±0.2
1.8±0.2
33
63.5±15.8
52.3±4.7
566.1±102.9
8.8±3.0
1.6±0.3
1.992
-8.648
-7.925
-7.925
0.998
0.260
0.000
0.000
0.000
0.174
CTDIvol, volume CT dose index; DLP, dose length product; ED, effective dose
DISCUSSION
The primary findings of this study were as follows: (1) MinDose sequence of DSCT could provide adequate
information of the coronary arteries with low radiation dose compared to standard retrospective sequence. (2)
In addition to LVEF, AVAD were in good agreement with ultrasound, the greater achievement of this study
was to be able to display the valvular and paravalvular structure by multi-slice CT images.
Coronary artery imaging
The response of the left ventricle to aortic valve disease is complex: studies have shown that patients could
sustain coronary adaptability reconstruction.
31
With the development of DSCT, its evaluation of the valve,
the overall and local cardiac function has been gradually discovered and used in clinical experience. 32 In our
study we chose MinDose sequence to reduce the radiation dose drastically without impairing image quality.
Our study is the first attempt to apply MinDose technology in the quantitative diagnosis of coronary artery
stenosis as well as to measure AVAD and LVEF in one examination. Forty aortic disease patients of
experimental group suspicious with CAD underwent DSCT examination before aortic valve replacement
since ultrasound alone cannot meet the heart surgeon requirements. For these patients DSCT was the
first-line option because it was non-invasive, safe, readily available and less expensive inspection compared
angiography.
AVAD measurements and paravalvular and valvular observation
There is no conclusion which phase should be chosen to calculate AVAD: at mid to end-systole or at
end-diastole? 20-21, 33-35 As we all know the aortic annulus ellipticity is changing throughout the cardiac cycle.
After discussion with cardiac surgery experts in our research center we believe that according to the actually
clinical experience the AVAD should be measured at end-diastole when the aortic annulus is the largest. Our
results showed that there was a strong correlation between AVAD measured by MinDose-DSCT and
intraoperation, both of their measurements can guide the choice of prosthetic valve model. Although
echocardiography can visually see the valvular calcification, prolapse situation, it is difficult to observe
lesions of the valve leaflets through continuously ultrasound views. Compared with TTE, DSCT cannot make
quantitative assessment of valvular stenosis and prolapse but has obvious advantages for observation of
valvular calcification, number of valve leaflets and valve prolapse. In addition, DSCT can measure the
diameter of the aortic root which the cardiac surgeons are very interested in before surgery at the midway
between the sino-tubular junction and sinuses of valsalva. Thanks to multiple planar reformations of CT
image, it is possible for aortic valve repair to become increasingly common despite its high technical
demands.
Cardiac function
This is the first study to compare 4D-echocardiography-derived measures of LVEF with DSCT-derived
modalities. Our study shows that there was a stronger correlation between LVEF measured by
MinDose-DSCT and 4D-TTE compared to MinDose-DSCT and 2D-TTE, both MinDose-DSCT and 4D-TTE
overestimated LVEDV and LVESV compared with 2D-TTE. We infer that the overestimation of LVEDV and
LVESV was attributed to the difference of computing mode. 2D-TTE speculated ventricular volume with the
modified Simpson’s method based on the measurement of two planes, while MinDose-DSCT and 4D-TTE
calculated volumes directly based on 3D-reformation. Variability and reproducibility analysis shows
MinDose-DSCT measurements of LVEF, AVAD are the highest reproducible data of the three methods.
Study limitations
Several limitations exist. This was a single-center study and the sample size was relatively small. Large
multiple-center studies are needed to confirm the findings of the study. It was also a retrospective study and
only a few patients accepted magnetic resonance (MR) inspection, so it is a pity we cannot compare data
from MinDose-DSCT to the gold standard of cardiac function-MR, multiple studies have shown that LVEF
and regional wall motion assessment with DSCT compares well with assessments by MR.
18, 36
We included
only patients with a stable and low HR (≤70bpm), and we still need further exploration about parameters of
MinDose sequence in patients with HR>70bpm. Furthermore, with two experienced readers, we were not
able to identify any potential influence of reader expertise on inter-observer agreement.
Conclusion
In conclusion, as a one-stop preoperative evaluation, MinDose sequence of DSCT can remarkably reduce
radiation dose without a deterioration of diagnostic image quality and comprehensively reflect the coronary
tree, AVAD and LVEF of patients with aortic valve disease.
References
1.
Petronio AS, Giannini C, Misuraca L. Current state of symptomatic aortic valve stenosis in the elderly
patient. Cir J 2011; 75: 2324-2325.
2.
Prodromo J, D'Ancona G, Amaducci A, Pilato M. Aortic valve repair for aortic insufficiency:a review. J
Cardiothorac Vasc Anesth 2012; 26:923-932.
3.
Milano AD, Faggian G, Dodonov M, et al.Prognostic value of myocardial fibrosis in patients with severe
aortic valve stenosis. J Thorac Cardiovasc Surg 2012; 144:830-837.
4.
Brown JW, Fehrenbacher JW, Ruzmetov M, Shahriari A, Miller G, Turrentine MW. Ross root dilation in
adult patients:is preoperative aortic insufficiency associated with increased late autograft reoperation?
Ann Thorac Surg 2011; 92:74-81.
5.
D’Onofrio A, Fusari M, Abbiate N, et al. Transapical aortic valve implantation in high-risk patients with
severe aortic valve stenosis. Ann Thorac Surg 2011; 92:1671-1677.
6.
Schulz O, Brala D, Bensch R, et al. Aortic Valve Replacement in Asymptomatic and Symptomatic
Patients with Preserved Left Ventricular Ejection Fraction. J Heart Value Dis 2012; 21:576-583.
7.
Otto CM, Lind BK, Kitzman DW, et al. Association of aortic-valve sclerosis with cardiovascular
mortality and morbidity in the elderly. N Engl J Med 1999; 341:142-147.
8.
Rajamannan NM. Calcific Aortic Valve Disease: Cellular Origins of Valve Calcification. J Arterioscler
Thromb Vasc Biol 2011; 31:2777-2778.
9.
Nistri S, Galderisi M, Faggiano P，et al. Practical echocardiography in aortic valve stenosis. J Cardiovasc
Med 2008; 9:653-665.
10. Reant P, Barbot L, Montaudon M, et al. Robustness of a new three-dimensional echocardiographic
algorithm for left ventricular volume and ejection fraction quantification: experts vs. novices. Eur J
Echocardiogr 2011; 12:895-903.
11. Dorosz JL, Lezotte DC, Weitzenkamp DA, Allen LA, Salcedo EE. Performance of 3-Dimensional
Echocardiography in measuring left ventricular volumes and ejection fraction: a systematic review and
meta-analysis. J Am Coll Cardiol 2012; 59:1799-1808.
12. Lan J, Mingxing X, Xinfang W, Li Y, Yuman L, Fengxia D. Clinical sdudy on left ventricular volume
and ejection fraction in normal subject by 4-Dimensional auto left ventricular quantification. J Clin
Cardiol(China) 2011; 27:460-463.
13.
Xu L, Zhang Z. Coronary CT angiography with low radiation dose. Int J Cardiovasc Imaging 2010;
26:17-25.
14. Yanhua D, Li W, Ximing W, et al. Application of prospective electrocardiogram-gated dual-source CT in
patients with acute chest pain. Chin J Radiol 2011; 45:32-36.
15. De Heer LM, Budde RPJ, Prehn J，et al. Pulsatile distention of the nondiseased and stenotic aortic valve
annulus: analysis with electrocardiogram-gated computed tomography. Ann Thorac Surg 2012;
93:516-522.
16.
Ocak I, Lacomis JM, Deible CR, Christopher R, Pealer K, Parag Y, Knollmann F.
The aortic
root:comparison of measurements from ECG-gated CT angiography with transthoracic echocardiography.
J Thorac Imag 2009; 24:223-226.
17.
Pflederer T, Jakstat J, Marwan M, et al. Radiation exposure and image quality in staged low-dose
protocols for coronary dual-source CT angiography:a randomized comparison. Eur Radiol 2010;
20:1197-1206.
18. Nakazato R, Tamarappoo BK, Smith TW, et al. Assessment of left ventricular regional wall motion and
ejection fraction with low-radiation dose helical dual-source CT:Comparison to two-dimensional
echocardiography. J Cardiovasc Comput Tomogr 2011; 5:149-157.
19. Jian L, Mingguo S, Minwen Z, Zhijun Y, Kai L. Application value of dose reduction techniques
(MinDose) in dual-source CT coronary artery angiography. Chin J Radiol Med Prot 2011; 31:95-97.
20. Fei T. ECG-pulsing combined with mindose technique in the radiation dose reduction of dual-source CT
coronary angiography. Chin J Med Imag 2011; 19:416-419.
21. Yongsheng H, Youzhi Z, Xinhua H, et al. A Preliminary study on low radiation dose dual-source CT
coronary angiography. Chin Comput Med Imag 2012; 18:122-127.
22. Kang Y. Application of body mass index and waist circumference for nutritional assessment among
obese individuals. Acta Acad Med 2010;Sin 32:4-6.
23. Leschka S, Scheffel H, Desbiolles L，et al. Image quality and reconstruction intervals of dual-source CT
coronary angiography. Invest Radiol 2007; 42:543-549.
24. Austen WG, Edwards JE, Frye RL，et al. A reporting system on patients evaluated for coronary artery
disease, report of the Ad Hoc Committee for Grading of Coronary Artery Disease, Council on
Cardiovascular Surgery, American Heart Association. Circulation 1975; 51:5-40.
25. Alkadhi H, Scheffel H, Desbiolles L，et al. Dual-source computed tomography coronary angiography:
influence of obesity, calcium load, and heart rate on diagnostic accuracy. Eur Heart J 2008; 29:766-776.
26. Feuchtner Gudrun, Goetti Robert, Plass Andrè，et al. Dual-step prospective ECG-triggered 128-slice
dual-source CT for evaluation of coronary arteries and cardiac function without heart rate control: a
technical note. Eur Radiol 2010; 20:2092-2099.
27. Hausleiter J, Meyer T, Hermann F，et al. Estimated radiation dose associated with cardiac CT
angiography. JAMA 2009; 301:500-507.
28. McCollough CH, Christner JA, Kofler JM. How effective is effectve dose as a redictor of radiation risk?
AJR Am J Roentgenol 2010; 194:890-896.
29. Gambarin FI, Massetti M, Dore R. The aortic root. Saremi F,Achenbach S,Arbustini E,Narula J.
Revisiting Cardiac Anatomy:A Computed-Tomography-based Atlas and Reference.1st ed. West sussex
UK: Wiley-blackwell, 2011:149-150.
30. Altiok E, Koos R, SchÖrder，et al. Comparison of two-dimensional and three-dimensional imaging
techniques for measurement of aortic annulus diameters before transcatheter aortic valve implantation.
Heart 2011; 97:1578-1584.
31. Kaufmann P, Vassalli G, Lupiwagna S, et al. Coronary artery dimension in primary and secondary left
ventricular hypertrophy. J Am Coll Cardiol 1996; 28:745-750.
32. Hamdan A, Guetta V, Konen E, et al. Deformation Dynamics and Mechanical Properties of the Aortic
Annulus by 4-Dimensional Computed Tomography. J Am Coll Cardiol 2012; 59:119-127.
33. Lang RM, Bierig M, Devereux RB, Flachskampf FA, Foster E, Foster E. Recommendations for chamber
quantification. J Am Soc Echocardiogr 2005; 18:1440-1463.
34. Pan WZ, Zhou DX, Pan CZ, Ge JB. Aortic valve annulus diameter in chinese patients with severe
calcific aortic valve stenosis: Implications for transcatheter aortic valve implantation. Catheterization and
Cardiovascular Interventions 2011; 9:720-725.
35. Altiok E, Koos R, Schröder J, Brehmer J, Hamada S, Becker M. Comparison of two-dimensional and
three-dimensional imaging techniques for measurement of aortic annulus diameters before transcatheter
aortic valve implantation. Heart 2011; 97:1578-1584.
36. Bauer RW, Kerl JM, Fischer N, et al.Dual-Energy CT for the assessment of chronic myocardial
infarction in patients with chronic coronary artery disease:comparison with 3-T MRI.AJR 2010;
195:639-646.