examination of the optimal temporal resolution required for computed tomography coronary angiography

Examination of the optimal temporal resolution requiredfor computed tomography coronary angiography

Kazuya Ohashi • Katsuhiro Ichikawa •

Masaki Hara • Tatsuya Kawai • Hiroshi Kunitomo •

Ryo Higashide • Yuta Shibamoto

Received: 12 February 2013 / Revised: 14 May 2013 / Accepted: 14 May 2013 / Published online: 26 May 2013

� Japanese Society of Radiological Technology and Japan Society of Medical Physics 2013

Abstract Sub-second multidetector-row computed tomog-

raphy systems provide great potential for the further

improvement of CT coronary angiography (CTCA).

However, because the temporal resolution (TR) of such CT

systems is insufficient, blurring and artifacts produced by

fast cardiac motion remain as unresolved issues. Previous

TR investigations of CTCA were based on the retrospec-

tive electrocardiogram-gated multisegment reconstruction

technique. However, the results obtained may not neces-

sarily be correct because the TR of multisegment recon-

struction may not be substantial due to the insufficient

periodicity of cardiac motion. The optimal TR required for

better CTCA images was evaluated with use of a dual-

source CT system, which has various substantial TR modes

(83, 125, and 165 ms). CTCA images of 147 patients with

heart rates (HRs) ranging from 36 to 117 beats/minute

(bpm) were evaluated visually on a 4-point scale. Our

results revealed not only that the 165-ms TR is sufficient

for low HRs (B60 bpm), but also that the 83- and 125-ms

TRs are unnecessary for such HRs. The image quality with

the 125-ms TR mode was acceptable for the left anterior

descending artery, left circumflex artery, and right coro-

nary artery at low to intermediate HRs (B70 bpm). At high

HRs ([70 bpm), the 83-ms TR mode resulted in an

excellent image quality for all cases except those with very

rapid RCA motion. Adequate TRs for a wide range of heart

rates (52–106 bpm) are thus clarified.

Keywords Dual-source CT � CT coronary angiography �Temporal resolution � Image quality � Motion artifact

1 Introduction

The rapid technologic development of multidetector-row

computed tomography (MDCT) systems over the past

decade has significantly increased the ability to image the

heart and the coronary arteries noninvasively. MDCT

systems have evolved from 4-detector-row systems to dual-

source CT (DSCT) and 320-row area detector CT (ADCT)

systems. With smaller detector element sizes and faster

gantry rotation speeds, spatial and temporal resolution (TR)

of MDCT systems has made CT coronary angiography

K. Ohashi (&) � H. Kunitomo � R. Higashide

Department of Radiology, Nagoya City University Hospital,

1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-0001,

Japan

e-mail: [email protected]

H. Kunitomo


R. Higashide


K. Ohashi

Graduate School of Medical Science, Kanazawa University,

5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan

K. Ichikawa

Institute of Medical, Pharmaceutical and Health Sciences,

Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa

920-0942, Japan


M. Hara � T. Kawai � Y. Shibamoto

Department of Radiology, Nagoya City University, Graduate

School of Medical Sciences, 1 Kawasumi, Mizuho-cho,

Mizuho-ku, Nagoya, Aichi 467-0001, Japan


T. Kawai


Y. Shibamoto


Radiol Phys Technol (2013) 6:453–460

DOI 10.1007/s12194-013-0218-1

(CTCA) a reliable clinical assessment tool [1]. Because

investigations on the measurement method of TR for

CTCA were few in number [2, 3], and a practical method

so far has not been established, most of the papers on

CTCA have used nominal TR values for TR descriptions,

which are generally indicated on consoles of CT systems or

in technical manuals provided by CT manufacturers.

Therefore, we also used nominal TR values in this paper. In

general, the nominal TR in CTCA scan modes indicates the

fraction of the cardiac cycle contributing to an image [4].

There are two typical scan methods for cardiac CT

imaging: the retrospective electrocardiogram (ECG)-gated

multisegment reconstruction technique, which uses the

helical scan mode, and the prospective ECG-gated half-

scan mode. Furthermore, a very high exposure dose is

required for the multisegment reconstruction technique

because of an extremely low pitch factor (\0.3), which is a

cause for concern [5]. Therefore, the half-scan mode,

which provides a lower exposure dose and higher image

quality, has been recommended for cases with low heart

rates (HRs) or with HRs decreased by beta-blockers [6].

ADCT has enabled low-dose volumetric imaging of the

entire heart within one cardiac cycle by use of the half-scan

mode [7]. However, the maximum TR of ADCT in the

half-scan mode is currently 165 ms, which is not sufficient

for HRs [65 beats/min (bpm) [8]. Therefore, further

improvements in the TR of ADCT and MDCT systems are

required for obtaining high-quality CTCA images for

patients not taking beta-blockers and having high HRs.

Previously published reports on potential improvements

in the image quality of CTCA were based on scan tech-

niques that used the multisegment reconstruction.

The multisegment reconstruction technique improves

the TR by dividing half-scan acquisition into two or three

cardiac phases; however, the TR does not necessarily

become half or one-third of the half-scan’s TR because

cardiac motion is not always constant, not only in HR but

also in vessel (wall) position within the cardiac cycle [9].

Thus, TR in the multisegment reconstruction technique is

not necessarily correct, and the relationship between TR

and CTCA image quality, which has been reported in such

investigations, may not necessarily be substantial [10].

From this perspective, the relationship between TR and

CTCA image quality needs to be reanalyzed with use of a

faster CT scanner and various substantial TR modes.

DSCT uses two X-ray tubes with opposing detector

arrays mounted at 90� from each other. The main advan-

tage of this system is that TR is effectively halved because

each X-ray tube/detector array system needs to rotate by

only half the angle that would otherwise be required by a

single-source system [11]. Because DSCT does not use the

multisegment reconstruction technique for CTCA, its TR is

substantial, making DSCT useful for analyzing the

relationship between TR and the image quality (mainly

motion artifacts) of CTCA. In addition, because the DSCT

system can reconstruct CTCA images with various TRs

from each item of raw data, the effect of TR in the same

patient can be evaluated by this function. However, such

investigations have not been conducted to date.

In this study, we utilized a DSCT system with three TR

modes (83, 125, and 165 ms) for analyzing the relationship

between TR and the degree-of-motion artifact. The images

of three TR modes were reconstructed from the same raw

data of one cardiac beats. The motion artifacts of the CTCA

images obtained with the three TRs were evaluated visually

for each coronary artery, and optimal TRs and reconstruc-

tion phases for various heart rate ranges were examined.

2 Materials and methods

2.1 Patient population

From January 1, 2010 to December 31, 2010, 147 con-

secutive patients (93 males and 54 females; mean age,

67 ± 10 years; range 33–91 years) who had undergone

CTCA were enrolled in this study. Patients were referred

for CTCA examinations to rule out coronary heart disease.

Inclusion criteria consisted of clinical indications for cor-

onary angiography (e.g., atypical chest pain, dyspnea),

sinus rhythm, renal function (estimated glomerular filtra-

tion rate [60 ml/min/1.73 m2), absence of hyperthyroid-

ism, and no history of allergy to iodine-containing contrast

agents. We excluded patients with coronary artery bypass

grafts and atrial fibrillation. The patients were divided into

three subgroups based on the HR recorded during the CT

scans: low HR (B60 bpm; 52–60 bpm), medium HR

(61–70 bpm), and high HR ([70 bpm; 71–106 bpm), as

shown in Table 1. All patients were in sinus rhythm. We

used the Chi-square test to compare categorical findings in

Table 1 Patient characteristics in the three subgroups divided

according to recorded heart rate (HR)

Low-HR

group

(n = 50)

Medium-

HR group

(n = 47)

High-HR

group

(n = 50)

p

Male/female 31/19 29/18 33/17 NS

Age (years) 69.0 ± 9.8 67.0 ± 10.6 66.1 ± 10.8 NS

Heart rate

during

imaging

(beats/min)

57.0 ± 2.5 65.0 ± 2.8 80.0 ± 8.3 \0.001

Body mass

index (kg/m2)

23.9 ± 3.5 23.4 ± 3.4 23.9 ± 4.0 NS

HR heart rate, NS not significant

454 K. Ohashi et al.

the patients’ data. This retrospective study was approved

by the local ethics committee.

2.2 Scan parameters and contrast agent injection

All patients were examined by use of DSCT, with each

patient placed exactly in the center of the CT gantry. Heart

rate modulation by beta-blocker administration was not

performed for any patient prior to CT, although 44 patients

(29.9 % of all patients) were under continuous beta-blocker

medication [12–14]. In the absence of contraindications,

nitrates were administered before CTCA for coronary

vasodilatation and for improved image quality [15, 16]. To

prevent artifacts due to breath-hold failure, a compression

belt wrapped around the chest and a nasal clip were used.

Data acquisition was performed from the level of the

tracheal bifurcation to the diaphragm in the craniocaudal

direction with a detector collimation of 32 9 0.6 mm and a

slice acquisition of 64 9 0.6 mm by means of a z-flying

focal spot. The gantry rotation time was 330 ms, and the

pitch factor was 0.2–0.5. The tube current was adapted

automatically to each patient’s weight by use of CareDose

4D automatic exposure control (CareDose 4D, Siemens

Medical Solutions, Forchheim, Germany) and with a ref-

erence tube current of 400 mAs for CTCA. The voltage

was 120 kV for both tubes. The ECG pulsing window was

65–75 % of the R–R interval when the baseline HR was

B60 bpm or 30–75 % of the R–R interval when the base-

line HR was [60 bpm. The mean scanning time was 9.3 s

(range 5.4–16.0 s), and the mean volume CT dose index

was 51.7 mGy (range 31.2–78.8 mGy). A test-bolus tech-

nique was performed for determining the contrast agent

transit time (20 ml of iopamidol containing 370 mg iodine/

ml, followed by 30 ml of isotonic saline, both at 5 ml/s) by

calculation of the time interval from the beginning of

contrast agent injection to the achievement of maximum

enhancement in the ascending aorta. For optimal contrast

enhancement of the coronary arteries, the total delay was

calculated by use of an additional time delay of 2 s. CTCA

was then performed after injection of 60–75 ml of contrast

agent at 5 ml/s, followed by 30 ml of saline. The amount of

contrast agent to be injected was estimated from the

expected duration of CT data acquisition; therefore, it

varied among patients.

2.3 Image reconstruction

Image reconstruction was performed while we paid close

attention to minimizing motion artifacts of each vessel

(Fig. 1). The start of the systolic reconstruction phase was

based on absolute timing, which was milliseconds after the

previous R pulse. The mean reconstruction timing was

291.4 ms (range 150–410 ms). The diastolic reconstruction

phase start was also based on absolute timing before the

next estimated R pulse, and the mean reconstruction phase

start was -246.3 ms (range -70 to -390 ms). Optimal

reconstruction phases with minimum motion artifacts for

three main vessels, namely, the left anterior descending

artery (LAD), left circumflex artery (LCX), and right cor-

onary artery (RCA), were determined by review of all

available cardiac phases at 5-ms intervals.

The CTCA image sets were reconstructed by use of the

three TR modes. Because the optimal phase was deter-

mined for each TR mode, the phase centers of the three TR

modes in each case were not necessarily identical. The

slice thickness, interval, and reconstruction kernel were set

to 0.75 mm, 0.4 mm, and B26f, respectively. The B26f

kernel is a smooth kernel for cardiac applications. All

images were transferred to an external workstation (Multi-

Modality Workplace, Siemens Medical Solutions, Forch-

heim, Germany) for further analyses.

2.4 Image quality evaluations

Image quality was evaluated visually by focusing on the

degree-of-motion artifacts in vessels. Two observers (A: a

Fig. 1 Examples of images of a coronary vessel for optimal reconstruction phases with minimum motion artifacts, milliseconds after the

previous R pulse: a left anterior descending artery, b left circumflex artery, and c right coronary artery

Examination of the optimal TR for CTCA 455

radiologist with 4 years of experience in CTCA diagnosis,

and B: a radiology technician with 6 years of experience in

CTCA imaging and image manipulation for vessel analy-

sis) assessed the axial images. The observers scored on a

4-point scale: 1 = strong motion artifacts, diagnostically

impaired; 2 = motion artifacts, diagnostically sufficient;

3 = little motion artifacts, diagnostically good quality, but

has little influence on plaque analysis; 4 = no motion

artifacts, excellent image quality (Fig. 2). All coronary

artery segments with a diameter of 1 mm were identified

following the 16-segment classification model of the

American Heart Association [17]. The left main trunk

(LMT), LAD, LCX, and RCA were divided into eight

sections. The section score of one vessel was given by

assignment of the lowest segment score for that vessel. We

statistically compared the image qualities of the three TR

modes, three HR subgroups, and each coronary artery by

using the Friedman and Tukey multiple comparison tests.

Interobserver agreement on image quality was assessed by

kappa analysis (\0.4: poor; 0.40–0.75: fair to good; [0.75:

excellent).

2.5 Stair-step artifact

Stair-step artifacts are caused by respiration, other body

movements, or irregularity of the HR over the cardiac

cycles during CT scanning. These may lead to an incorrect

diagnosis of pathological stenosis. In DSCT CTCA images,

the artifacts appear as clear displacements, as shown in

Fig. 3. In contrast, the artifacts do not necessarily present

such clear changes in multisegment reconstruction images

and may be misinterpreted as a kind of heartbeat motion

artifact. Therefore, we evaluated the correct frequency of

the stair-step artifact from DSCT CTCA images. Because

Fig. 2 Examples of images of

a coronary vessel (right

coronary artery) for respective

scores: 1 strong motion artifacts,

diagnostically impaired; 2

motion artifacts, diagnostically

sufficient; 3 little motion

artifacts, diagnostically good

quality, but has little influence

on plaque analysis; 4 no motion

artifacts, excellent image

quality

Fig. 3 Examples of stair-step artifacts in a coronal, b oblique, and c sagittal multiplanar reformatted images of the right coronary artery


coronal- and sagittal-plane reconstruction makes the arti-

facts more obvious [18], the same two observers as in the

image evaluation counted the incidence of stair-step arti-

facts on coronal and sagittal multiplanar reformation ima-

ges (1-mm thickness) that were reconstructed from the

axial CTCA images. The 83-ms (shortest) TR mode was

used for this investigation because the mode was effective

for evaluation of the stair-step artifacts as clear

displacements.

3 Results

Figure 4 shows the results of visual evaluation of the

respective vessels. Table 2 shows the detailed results for all

segments. Mean scores for the eight segments at B60 bpm

were not significantly different between the 83-ms TR

(4.0 ± 0.0) and 165-ms TR (4.0 ± 0.1) modes as well as

between the 83-ms TR (4.0 ± 0.0) and 125-ms TR

(4.0 ± 0.1) modes (Table 2). The 165-ms TR mode, which

is available on most modern MDCT systems, resulted in

sufficient image quality for all vessels only at low HRs

(B60 bpm) (Fig. 4). At low to intermediate HRs

(\70 bpm), the 125-ms TR mode resulted in sufficient

image quality for LAD and LMT (4.0 ± 0.0), LCX

(4.0 ± 0.0), and RCA (3.7 ± 0.7) (Table 2). At the high

HR ([70 bpm), the 83-ms TR mode resulted in excellent

image quality for all cases except those with very fast RCA

motion (3.6 ± 0.5) (Table 2). Scores for RCA were infe-

rior to those for LAD, LMT, and LCX in almost all of the

HR subgroups (Table 2).

We performed an interobserver reliability analysis by

use of the kappa statistic to determine the consistency

among the two readers. The interobserver Kappa values of

the low-, medium-, and high-HR subgroups were 0.901

(95 % CI 0.876–0.926), 0.886 (95 % CI 0.851–0.921), and

0.836 (95 % CI 0.760–0.912), respectively.

Table 3 shows the rates of systolic and diastolic phases

in the determined phases that provide minimal motion

artifacts. For all vessels, the systolic-phase rates increased

with an increase in the HR, and the RCA indicated the

highest systolic-phase rates among all vessels.

We tried to suppress stair-step artifacts by carefully

instructing patients on breath-holding and staying still.

However, as shown in Table 4, on overall stair-step inci-

dence rate of 15.6 % was unavoidable.

4 Discussion

In this study, we investigated the relationship between

CTCA image quality and various substantial TRs, which

can be achieved with use of the DSCT single-segment scan

technique. Because we obtained CTCA images with three

TRs by using different reconstruction modes, a more con-

sistent analysis than previous reports regarding TR of the

cardiac CT could be performed. To date, no studies have

focused as carefully on the TRs as we did in our study.

Fig. 4 Results of visual evaluation of each artery, and of all vessels

for the three heart rate subgroups: a right coronary artery, b left

anterior descending artery and left main trunk, c left circumflex

artery, and d all vessels. *p \ 0.05, **p \ 0.001, NS not significant


From the results we obtained, adequate TRs for a wide

range of HRs (52–106 bpm) were clarified. Of the three TR

modes, the 83-ms mode demonstrated excellent image

quality for all cases except those with very rapid RCA motion.

Therefore, further improvement in the TR is required for

obtaining good image quality at high HRs. Of late, heart

perfusion blood volume examinations have been made pos-

sible by utilization of the dual-energy modes of DSCT [19,

20]. However, TR deterioration caused by the dual-source

usage for the dual energy is a cause for concern. The results of

this study have indicated that the dual-energy mode of DSCT

can be used for RCA imaging in cases with HRs B60 bpm

and LAD, LMT, and LCX imaging in cases with

HRs B70 bpm. The fastest gantry rotation speed in current

MDCT systems with a single source is 0.27 s per rotation

with a TR of 135 ms (iCT, Philips Medical Systems, Best,

The Netherlands). If it is assumed that the 135-ms TR mode is

nearly equal to the 125-ms TR mode, the MDCT can be used

Table 2 Mean scores of

respective coronary segments

for the three temporal resolution

modes

HR heart rate, LAD left anterior

descending artery, LMT left

main trunk, LCX left circumflex

artery, RCA right coronary

artery

Coronary artery Section (coronary segment) 83 ms 125 ms 165 ms

Low HR RCA 1 (#1) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

2 (#2) 4.0 ± 0.1 4.0 ± 0.2 3.9 ± 0.3

3 (#3, 4) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

LAD, LMT 4 (#5, 6) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

5 (#7, 9) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

6 (#8, 10) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

LCX 7 (#11, 12) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

8 (#13, 14, 15) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

Mean (#1–15) 4.0 ± 0.0 4.0 ± 0.1 4.0 ± 0.1

Medium HR RCA 1 (#1) 3.9 ± 0.3 3.8 ± 0.5 3.6 ± 0.7

2 (#2) 3.8 ± 0.4 3.7 ± 0.6 3.2 ± 0.8

3 (#3, 4) 3.9 ± 0.3 3.7 ± 0.7 3.5 ± 0.9

LAD, LMT 4 (#5, 6) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

5 (#7, 9) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.2

6 (#8, 10) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.2

LCX 7 (#11, 12) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

8 (#13, 14, 15) 4.0 ± 0.0 4.0 ± 0.0 4.0 ± 0.0

Mean (#1–15) 3.9 ± 0.2 3.9 ± 0.3 3.8 ± 0.5

High HR RCA 1 (#1) 3.9 ± 0.4 3.7 ± 0.5 3.1 ± 0.9

2 (#2) 3.7 ± 0.5 3.4 ± 0.7 2.8 ± 0.9

3 (#3, 4) 3.6 ± 0.5 3.1 ± 1.0 2.6 ± 1.0

LAD, LMT 4 (#5, 6) 4.0 ± 0.1 4.0 ± 0.1 4.0 ± 0.2

5 (#7, 9) 4.0 ± 0.1 4.0 ± 0.2 3.9 ± 0.4

6 (#8, 10) 4.0 ± 0.1 4.0 ± 0.2 3.9 ± 0.3

LCX 7 (#11, 12) 4.0 ± 0.2 3.9 ± 0.5 3.8 ± 0.6

8 (#13, 14, 15) 4.0 ± 0.2 3.8 ± 0.4 3.5 ± 0.7

Mean (#1–15) 3.9 ± 0.3 3.7 ± 0.6 3.5 ± 0.9

Table 3 Rates of systolic and diastolic phases in determined phases

that provide minimal motion artifacts for each heart rate subgroup

Coronary

artery

Reconstruction

phase

Low HR

(%)

Medium HR

(%)

High HR

(%)

RCA Diastole 100.0 88.9 34.2

Systole 0.0 11.4 65.6

LAD, LMT Diastole 100.0 97.5 67.7

Systole 0.0 2.5 32.3

LCX Diastole 100.0 97.5 68.8

Systole 0.0 2.5 31.2

Mean Diastole 100.0 94.6 56.9

Systole 0.0 5.5 43.0

HR heart rate, LAD left anterior descending artery, LMT left main

artery, LCX left circumflex artery, RCA right coronary artery

Table 4 Incidence rates of stair-step artifacts

Low HR

(%)

Medium HR

(%)

High HR

(%)

Overall

(%)

Stair-step

artifact

7/50

(14.0)

8/47 (17.0) 8/50

(16.0)

23/147

(15.6)

HR heart rate


without beta-blocker medication for imaging of all vessels in

cases with HRs B70 bpm. Higher rotation speeds in single-

source CT systems may be required for improvement of the

CTCA image quality with HR [70 bpm. However, for

obtaining an acceptable image quality with less noise, a very

large tube load is required for fast rotation speeds, and it is

thought that this may impede efficiency. Therefore, we

believe that DSCT is effective for both TR improvement and

maintaining image quality.

Our results revealed not only that the 165-ms TR is

sufficient for the low HRs (B60 bpm), but also that 83- and

125-m TRs are unnecessary for such HRs. These finding

might suggest that selection of slow rotation speeds in the

fastest MDCT system or DSCT system can be allowed for

the low HRs. With the slow rotation speed, it is expected

that the image resolution is improved due to the increased

projections, and that the patient dose is reduced in the

prospective gating scan modes when the same exposure

time window is used.

The guidelines of the Society of Cardiovascular Com-

puted Tomography state that systolic-phase reconstruction

is better for patients with high HR ([65–70 bpm). Sun

et al. evaluated the quality of systolic-phase DSCT images

of patients with high HRs ([70 bpm) and found that the

image quality for the RCA was superior to that for the LAD

and LCX [21]. However, they evaluated image qualities for

all arteries from images obtained in only one phase. In

contrast, we determined the optimal reconstruction phase

with the least artifacts for each artery from image sets

obtained in many phases with 5-ms intervals. In our results,

RCA image quality was inferior to LAD and LCX image

quality in the medium- and high-HR subgroups.

Stair-step artifacts were observed in 23 (15.6 %) of the 147

cases examined. Because the artifact is misinterpreted as an

artifact of heartbeat motion in some multisegment recon-

struction CTCA images, we believe that the incidence rate of

this artifact was not clarified in past studies. Although com-

parison studies of DSCT and MSCT image quality have been

performed in the past [22, 23], they have not demonstrated the

incidence rate of the stair-step artifact.

Because the DSCT system employed by us was not the

latest system, the maximum TR mode was limited to an

83-ms mode, which is inferior to the 75-ms TR mode in the

latest DSCT systems. If a similar investigation is conducted

with the latest DSCT system, the maximal HR at which

sufficient RCA image quality can be obtained would be

raised to the high HRs, more than 70 bpm.

5 Conclusions

In conclusion, the relationship between HR and CTCA

image quality for three TR modes was assessed by use of

three reconstruction modes with substantial TRs of 83, 125,

and 165 ms, provided on a DSCT system. Consistent

relationship results, which have not been reported in pre-

vious papers, were obtained. The 165-ms TR mode, which

is available on most modern MDCT systems, was sufficient

only for cases with HRs \60 bpm. The image quality with

the 125-ms TR mode was acceptable for the LAD, LCX,

and RCA at low to intermediate HRs (B70 bpm). At high

HRs ([70 bpm), the 83-ms TR mode demonstrated

excellent image quality for all cases except those with very

rapid RCA motion.

Conflict of interest None.

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examination of the optimal temporal resolution required for computed tomography coronary angiography

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