Journal of Biosciences and Medicines, 2013, 1, 6-10 JBM
doi:10.4236/jbm.2013.11002 Published Online February 2013 (http://www.SciRP.org/journal/jbm/)
Published Online February 2013 in SciRes. http://www.scirp.org/journal/jbm
Exploration th e Met h od of Low Dose Coronar y Art ery
Imaging with Dual-Source CT
Zhiwei Huang, Bo Xiao, Lisha Zhong
Department of Bio medi cal Engineering, Lu zhou Medical Co llege, Luzhou, P.R.China
Received 2013
ABSTRACT
Objective: On the pre mise that the image q uality meets
the requirements of clinical diagnosis, we explored
the methods to reduce the radiatio n dose of coronary
artery imaging with Dual-Source CT (DSC T) . Metho d s:
We randomly selected 200 patients with coronary
heat disease (BIM<25kg/m2), applied the scanning
technology of regulating the dose of heart electric
pulse (AUTO) on t he 100 patients in group A . In this
group for different heart rate we chose different full
dose exposure time window. For the 100 patients in
group B, we used conventional full dose (OFF) scan
mode. The DSC T a uto mat ic ally selec ted t he be st t i me
and phase to reconstruct the image. We used the 5
point system to evaluate the image quality, measured
and compared the image noise and radiation dose.
When P<0.05, t he differences between the two groups
have statistical significance. Results: The image
quality scores between the two groups showed no
significant difference (P > 0.05). The average image
noise in gro up A is (41.76 ± 7.98) HU, in group B the
average image noise is (43.97 ± 3.88) HU, the dif-
ference between the two groups was not statistically
significant (P>0.05). The average CTDIvol of group A
and B were (20.63 ± 2.24) mGy, (38.11 ± 10.69) mGy,
respectively, then P <0.01. The average DLP of group
A and B are (235.75 ± 28.64) mGycm and (492.59 ±
125.49) mGycm respectively, then P <0.01, the dif-
ference of radiation dose had statistical significance
(P<0.05). Conclusions: For coronary artery imaging
with DSCT the heart electric pul se (AUTO) regulation
technology can meet the diagnostic requirements and
effectively reduce the radiation dose.
Keywords: Dual-Sou rce CT(DS C T); Corona ry CT
Angiog raphy; L ow dose ; N oi s e;
1. INTRODUCTION
The study sho ws that t he DSCT c oronar y arter y imagin g
has a hi gh d egre e of consistency in the diag nostic results
of coronary stenosis and selective coronary arteriongra-
phy (SCA) [1]. DSCT evaluation on moderate to severe
coronary artery stenosis has higher compliance and con-
sistency with the SC A, DSCT can be used as a noninva-
sive conventional means in clinical screening and diag-
nosis [2]. DSCT has two sets of X-ray tubes and relative
detectors, two sets of DAS systems are installed in 90
degree angle on the rack. Compared with multi-slice
spiral CT ( MSCT), DSCT reaches higher time resol ution,
its detector covers more areas, its scanning speed be-
comes fa ster, so the scan time is gre atly shor ten, and the
radiation doses is significantly reduced by about 15% to
20% [3]. It also has other advantages, such as the pitch
can be automatically adjusted with the heart rate without
the limit of the heart rate, and the negative prognosis is
high [4]. With the appearance of DSCT, the radiation dose
is reduced, but the radiation dose is still widely con-
cerned. The heart disease committee declared that if
2000 patients receive CT examination with the radiation
dose of 10mSv, one of them will suffer from malignant
tumors. For the overall risk of cancer caused by radiation,
male is less than the women, and the gap between men
of different ages, and there is little gap between men of
different ages; but the overall cancer risk of women de-
creases with increasing age [5]. In this paper for coronary
artery imaging with DSCT, we compared heart electric
pulse (AUTO) wit h conventional full-dose (OFF) sc an
mode, compared the image quality, image noise, and
radiation dose of the two sets. Ensurin g the quality of the
image to meet the diagnostic requirements, we tried to
find methods to minimize the radiatio n d ose.
2. MATERIALS AND METHODS
2.1. Case Selection
From May 10, 2012 to May 25, 2012, we randomly se-
lected 200 patients from West China Ho spital of Sichuan
University, these patients were clinical suspected or di-
agnosed with coronary heart disease (BIM<25kg/m2).
100 cases are in group A (63 cases are male, female 37

Z. W. Huang et al. / Journal of Biosciences and Medicines 1 (2013) 6-10
7
cases are female, their ages were 34 - 82 years old, the
average age was 58 years old ), and in their scanning
mode, we used AUTO scanning mode . Another 100 cas-
es ar e i n gro up B (5 7 cases are male, 43 cases are female,
their ages were 33 - 80 years old, their average age is
56.5 years old), we applied OFF scanning mode on them.
Two groups of patients are not restricted by heart rate,
age and gender, except serious arrhythmia or frequent
premature beats patients. In b oth groups we used retros-
pective cardiac-gated imaging technique.
2.2. Scanning Preparation
We tried to understand whether patients are allergic to
iodine, and their renal functions are normal. We also
tried to eliminate the tension and depression of the pa-
tients. We conducted strict breath training on patients,
and e njoined patie n ts to keep respiratory amplitude con-
sistent for ever y time. The patients are in the supine po-
sition, the feet of the patients entered the CT gantry first.
ECG electrodes were correctly placed, and the leads
with higher R wave were selected. For the patients
without hypotension, we sprayed Nitroglycerin Aerosol
2-3 times under their tongues.
2.3. Scanning Method
2.3.1. Scanning O peratio n
We used the Siemens Somatom Definition as DSCT
scanner. For the patients in group A and B, we applied
the same time resolution, space resolution, rotation
time(0.33s), collimator width (64*0.6mm), image recon-
struction thickness (0.75mm), reconstruction interval
(0.5mm). At the same time, the scanning range (from 1
to 2cm under the bifurcation of trachea to diaphragmatic
surface of heart), contrasted medium injection scheme,
and image processing methods were kept consistent. We
chose Iopamidol (370 mgI/ml) contrast agent and Ger-
many binocular high-pressure syringe (Ulrich Medical),
Syringe needle was placed on the forearm vein. Firstly
physiological saline was injected, then contrast agent
Iopamidol was injected, at last physiological saline was
injected.
2.3.2. Iodine Concentration Monitoring
We used contrast agent tracer method. In the center of
ascending aorta (it is under the tracheal bifurcation and
away from the bi f urc atio n 2-3cm), we chose the region
of interest and detected the CT value, and the threshold
value was set to 100HU. When the CT values in the re-
gion o f i ntere st reac h 100 H U, the CT will automatically
trigge r sca n with a delay of 6s. Pay attention to avoiding
the impact of the superior vena cava.
2.3.3. ECG
We scanned the patients after their heart rate was steady
and used AUTO scanning mode: the exposure range of
the full dose scan mode was a certain time window in
the R-R interval, and the rest exposure dose was 1/4 of
the ful l d ose. The ti me wi ndow o f the ful l do se exp os ure
was in the R-R interval, and this time window corres-
ponded to different heart rate range. For relativel y fast or
slow heart rate, the ful l-dose exposure range in R-R in-
terval was the smallest. For normal heart rate, full-dose
expo sure ran ge was the maximum. O FF scanning mode:
the full dose-exp osure ra nge is the entire R-R interva l .
2.3.4 Ima ge Pos t-processing
We adopted Siemens Syngo Miltimodalit y Workp lace as
the workstation software for automatically selecting the
best time and phase. By calculating the movement speed
of each vessel coronary, the best time and phase were
selected for reconstruction of 0.75mm thickness, so we
got the best corona ry a rtery i mages at systole and dia stole.
We used the software Circulation to perform the image
post-processing, main technologies includes: Maximum
Intensity Projection, Curved Surface Reconstruction),
Volume Reproduction in order to multi-facedly show the
left main of coronar y artery and its main branches Right
Coronary Artery, Anterior Descending and Circumflex
Artery.
2.4. Image Quality Assessment and Radiation
dose Calculation
2.4.1. Image Quality Assessment
Two experienced diagnostic physicians rated images by
using the double-blind method. For the inconsistent
judgments, they jointly and secondly read the film to
reach agreement. We used 5-p oi nt sc al e in t he gr ad i ng of
the image quality. The standard of 5 points is that the
image can be display clearly without artifacts, the blood
flow filling in all the vascular is good. The stand ard o f 4
points is that there is minor artifacts, only a certain sec-
tion o f the mai n cor onar y arte ry is sligh tl y fuzz y without
split-level or ladder-like artifacts, the diagnosis is not
affected. The standard of 3 points is that in the film the
artifacts are medium, more than 1/2 of one coronary ar-
tery trunk is fuzzy, but we can diagnose the illness. The
axial image is rather vague, but the reconstructed image
can be used for diagnosis. The standard of 2 points is
that in the film the artifacts are severe, all the parts of
one coronary artery are fuzzy or discontinuous, parts of
the blood vessels ha ve split-level artifacts, and the diag-
nosis is limited. The standard of 1 point is that the coro-
nary artery can not be recognized, the tube p ulse can no t
be analyzed, and we can not diagnose the illness. If the
score of the image quality can reach 4-5 points, the im-
age can be considered to be a high-quality image; if the
score is 3 points, the image is evaluated image; if the

Z. W. Huang et al. / Journal of Biosciences and Medicines 1 (2013) 6-10
8
score is 1-2 points, the image has severe artifacts, it can
not be evaluated and is poor image [6].
2.4.2. Radiatio n dose and Image Noise
The dose of X-ray is provided by the equipment. ED is
the effective dose of ra d ia tion in the patient, and it can
be calculated by using the formula ED = DLP × k, where
k=0.017 [7] and DLP is the dose length product. DLP
(myGycm) is displayed on the device. CTDIvol is CT
dose index, it is also displayed on the device. We set
1cm2 region of interest (ROI) which is put on aortic
center, the ROI is on the beginning part of the left and
right coronary arter y and it is also on the level aortic roo t.
We measured the ROI’s CT value, used the value s’ stan-
dard deviation as the image noise. We calculated the
average value of the twice CT values in the left a nd rig ht
coronary artery, and used this average value as the ulti-
mate CT value. Similarly, the average value of the stan-
dard deviation was calculated twice.
2.5. Statistical Method
We analyzed the obtained data by using software
SPSS11.5. We compared the scores’ differences of image
quality between two groups by applying the values of
χ2. We also applied two independent samples t to test
and compare the radiation dose and image noise. If
P<0.05, we thought the difference had statistical signi-
ficance [8].
3. RESULTS
3.1. Image Quality
In Group A, we got 76 cases, for which the score of im-
age quality was 5 point, accounting for 76%. At the same
time we got 4 points in 20 cases, accounting for 20% and
3 points in 4 cases, accounting for 4%, 2 points and 1
point, 0 cases, accounting for 0%. In group B, we got 5
points in 84 cases, accounting for 84% and 4 points in 14
cases, accounting for 14%, 3 points in 2 cases, account-
ing for 2%, 2 points and 1 point 0 cases, accounting for
0% (Shown in Tabl e 1). For all the coronary artery im-
ages whose quality can be evaluated, the difference of
scores between two groups showed no significant dif-
ference (P> 0.05).
Table1. The comparison of the image quality in Group A and
B.
3.2. Image Noise
The average CT value in Group A is (475.1 ± 45.75) HU,
the a vera ge CT va lue i n Group B is (451.1 ± 45.77) HU,
P>0.05. The average image noise in Group A is (41.76 ±
7.9 8) HU, the average i mage noi se in Gro up B is ( 43.97
± 3.88) HU, P> 0.05. The difference of image nose be-
tween Group A and B had no statistical significance, as
sho wn in fol lo wi ng Table 2.
3.3. Radiation Dose
The radiation dose in the process of cardiac coronary
artery examination consists of the following 3 parts:
Scan, Contrast Agent Tracer Scan and Enhanced Scan.
The radiation dose is the sum of these three parts. We
did statistical analysis, and calculated CTDIvol, mean
dose length product (△DLP) and ED, we also compared
the results. In Group A, the average CTDIvol is (20.63 ±
2.24) mGy, in Group B the average CTDvol is (38.11 ±
10.69) mGy, it reduced (17.48 ± 8.45) mGy, and it de-
creased by nearly 1 time, P <0.05. In Group A, the △
DLP is (235.75 ± 28.64)mGycm, in Group B the △DLP
is (492.59 ± 125.49) mGycm, it reduced (256.84 ± 96.85)
mGycm, it decreased more than 1 time, P <0.05. In
Group A the average ED is (4.01 ± 0.49) mSv, in Group
B the average ED is (8.37 ± 2.13) mSv, it reduced (4.36
± 1.64) mSv, it decreased more t h a n 1 t i me , P<0.05. The
radiation dose difference between two groups was statis-
tically significant, as shown in Table 3.
4. DISCUSSIONS
DSCT coronary artery imaging in the diagnosis of car-
diovascular diseases has unique advantages, more and
more clinical cardiologist take CT as an important
Table 2. Comparison of the image noise in Group A and B.
Table 3. Comparison of the radiation dose of the Group A and
B

Z. W. Huang et al. / Journal of Biosciences and Medicines 1 (2013) 6-10
9
examination tool for non-invasive coronary artery imag-
ing, it can be used as a supplement Cardiovascular Angi-
ography, sometimes it can even replace Cardiovascular
Angiography. In the process of the entire examination of
DSCT, X-ray dose is large, the radiation hazards it pro-
duces gets more and more attention. In order to follow
the principle of ALARA (as low as reasonable achieva-
ble), many scholars have done a lot of research in this
respect, including hardware, software and optimizing
programs of scan, such as Heart Bowtie, ECG Current
Control, Cardiac noise subtraction filter, etc [9]. But the
factors which affect the image quality are complex, some
of these factors are closely related and influence each
other. Some parameter settings may improve the image
quality, but on the other hand, they may reduce the im-
age quality in another aspect. So we must comprehen-
sivel y co ns i de r, and separately set the parameters of scan
according to the different clinical needs. But it is diffi-
cult for us to balance the various factors to obtain
high-quality images in order to improve the diagnostic
rate. Cur ren tl y, the re i s no sta nda rd for q ualit y co ntr ol i n
cor onar y arter y ima gi ng o f Dua l-So urce CT in o ur co un-
try.
So far, people have paid more and more attention to
the potential hazards of ionizing radiation in CT. When
ionizing radiation is wo rk ing on human body, it can
produce biological impacts and do harm to human body.
The break of the structure of DNA double helix in hu-
man body is the critical damage to the cells. Radiation
induces gene mutations or the break of the double helix
structure, the distortion increases, and eventually, the
radiation can lead to cancer [10]. The reports pointed out
that for every more radiation dose of 10mSv, the mortal-
ity rate will increase by 0.04% [11]. The actual radiation
dose of CT examination is 2-5 times the dose of effec-
tive radiation [12]. The dose of effective radiation mainly
comes from the enhanced period. In the aspect of opti-
mizing scanning program, people mostly focus on con-
trolling the radiation dose of enhanced period. In most
cases, the image quality and the radiation dose have the
inverse relationship. To balance the relationship between
them, we need to change the fixed scan mode. In prac-
tical application, we should pay attention to the individ-
ual conditions of the different patients, such as the size
of the heart, breast size of the female patient s and cardi-
othoracic ratio, etc. According to these conditions, we
determine the appropriate scan mode and scan parame-
ters. So we can achieve the personalized and reasonable
scanning. A recent survey, which is an international re-
search for radiation dose in coronary artery CTA, dis-
plays that the radiation dose in different hospitals have
obvi ous gap , fro m an a vera ge of 5 mSv to an a verage of
30 mSv. This demonstrates that reasonable scan mode
can effectively reduce the radiation dose [13]. Therefore,
on the premise that the ima ge quality meets the require-
ments of clinical diagnosis, it becomes important for us
to effectively reduce the radiation dose in the CTA ex-
amination of coronary artery, and this can reduce the
radiation damage caused by human factors.
Reducing the radiation dose is generally divided into
two categorie s: new low-dose technology and optimizing
scan parameters. The new scanning technology uses the
ECG current modulation technique, Prospective ECG
Trigger Scan Technology and noise red uction al gorithms.
The methods of optimizing scan parameters are lowering
tube current, lowering tube voltage, reducing the scan
rage of Z-axis and reducing the number of scans based
on body mass or body mass index (BMI). In this article,
in order to reduce the radiation dose, we used the tech-
nology of regulating the dose of heart electric pulse
(AUTO), and this technology belongs to retrospective
cardiac-gated i magin g techniq ue. T hrough t he stud y and
analysis, we concluded that the regulation technology of
dose of heart electric pulse (AUTO) can make the image
quality completely meets the requirements of clinical
diagnosis, and compared with the conventional full dose
(OFF), thi s techno logy can significa ntly reduce the radi-
ation dose of (4.36 ± 1.64) mSv, the radiation dose de-
creased more than 1 time. Of course, it also has inade-
quacies: 1. Data acqui sition is not ca rried o ut throughout
the whole cardiac cycle, and we can not analyze the car-
diac function. 2. If the patient’s heart rate in unstable, it
is easy for us to select the wrong full-dose regions. 3. In
the non-full-dose exposure regions of the R-R interval,
the image quality is a little bit worse than that of the
image in full-dose regions. 4. If there are heart prema-
ture beats in the scan, we can not edit the ECG.
The study has t he follo wing limitatio ns. T he ind ividu-
alized scan mode according the patient’s BMI was not
adopted, the radiation dose still has some space to be
reduced, a nd i n thi s a sp ec t t he study s ho uld b e c o nti nue d.
If the post-processing of image only uses one of the two
periods in image reconstruction, we can only reconstruct
the image of one period, therefore the radiation dose will
be reduced by 1 time, and in this aspect can be studied
much fur t her.
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