Prospective ECG-triggering Research Articles

Prospective ECG-Triggered Coronary CT Angiography: Clinical Value of Noise-Based Tube Current Reduction Method with Iterative Reconstruction

ObjectivesTo evaluate the clinical value of noise-based tube current reduction method with iterative reconstruction for obtaining consistent image quality with dose optimization in prospective electrocardiogram (ECG)-triggered coronary CT angiography (CCTA).Materials and MethodsWe performed a prospective randomized study evaluating 338 patients undergoing CCTA with prospective ECG-triggering. Patients were randomly assigned to fixed tube current with filtered back projection (Group 1, n = 113), noise-based tube current with filtered back projection (Group 2, n = 109) or with iterative reconstruction (Group 3, n = 116). Tube voltage was fixed at 120 kV. Qualitative image quality was rated on a 5-point scale (1 = impaired, to 5 = excellent, with 3–5 defined as diagnostic). Image noise and signal intensity were measured; signal-to-noise ratio was calculated; radiation dose parameters were recorded. Statistical analyses included one-way analysis of variance, chi-square test, Kruskal-Wallis test and multivariable linear regression.ResultsImage noise was maintained at the target value of 35HU with small interquartile range for Group 2 (35.00–35.03HU) and Group 3 (34.99–35.02HU), while from 28.73 to 37.87HU for Group 1. All images in the three groups were acceptable for diagnosis. A relative 20% and 51% reduction in effective dose for Group 2 (2.9 mSv) and Group 3 (1.8 mSv) were achieved compared with Group 1 (3.7 mSv). After adjustment for scan characteristics, iterative reconstruction was associated with 26% reduction in effective dose.ConclusionNoise-based tube current reduction method with iterative reconstruction maintains image noise precisely at the desired level and achieves consistent image quality. Meanwhile, effective dose can be reduced by more than 50%.

Coronary computed tomography angiography with prospective electrocardiography triggering: a systematic review of image quality and radiation dose

The purpose of this study was to perform a systematic review of the diagnostic accuracy, image quality and radiation dose of prospective electrocardiography (ECG)-triggered coronary computed tomography angiography (CCTA). We searched databases containing studies of CCTA that used prospective ECG-triggering between 2008 and 2011. The effective dose and image quality reported in each study were analysed and compared between the types of multislice CT scanners. We identified 23 studies through this search, with mean assessable coronary segments and effective dose at 96.8% (95% confidence level [CI] 83%, 100%) and 3.6 mSv (95% CI 2.9, 4.3 mSv), respectively. Both quantitative and qualitative assessments of image quality indicated that image quality was achieved in studies using prospective ECG-triggered CCTA, regardless of the type of CT scanners. The pooled estimates of diagnostic values were more than 90% for patient-, vessel- and segment-based assessments. Prospective ECG-triggered CCTA results in high diagnostic accuracy and image quality, with a significantly low radiation dose.

Optimizing contrast medium injection protocol individually with body weight for high-pitch prospective ECG-triggering coronary CT angiography

To individually optimize contrast medium protocol for high-pitch prospective ECG-triggering coronary CT angiography using body weight. Ninety patients undergoing high-pitch coronary CT angiography were randomly assigned to 3 contrast medium injection protocols with bolus tracking technique: Group A, 0.7 ml CM per kg patient weight (ml/kg); Group B, 0.6 ml/kg; Group C, 0.5 ml/kg. Each group had 30 patients. The CT values of superior vena cava (SVC), pulmonary artery (PA), ascending aorta (AA), left atrium (LA), left ventricle (LV), left main artery (LM) and proximal segment of right coronary artery (RCA) were measured. The image quality of coronary artery was evaluated on per-segment basis using a 4-point scale (1-excellent, 4-non-diagnosis). The CT value was not significantly different on AA (p = 0.735), LM (p = 0.764), and proximal segment of RCA (p = 0.991). The CT value was significantly different on SVC, PA, LA and LV (all p < 0.05). The mean image quality score was 1.6 ± 0.1, 1.6 ± 0.1 and 1.6 ± 0.1 (p = 0.217). The volume of CM was 47 ± 8, 44 ± 8 and 36 ± 6 ml for 3 groups (p < 0.001). The effective radiation dose was 0.88 ± 0.04, 0.87 ± 0.06, and 0.85 ± 0.07 mSv for 3 groups. Contrast medium could be reduced to 0.5 ml/kg for high-pitch coronary CT angiography without compromising diagnostic image quality, which associated ~50 % reduction of total contrast volume compared with standard contrast protocol with test bolus technique.

Low-dose CT coronary angiography using iterative reconstruction with a 256-slice CT scanner

To explore whether computer tomography coronary angiography (CTCA) using iterative reconstruction (IR) leads to significant radiation dose reduction without a significant loss in image interpretability compared to conventional filtered back projection (FBP). A consecutive series of 200 patients referred to our institution to undergo CTCA constituted the study population. Patients were sequentially assigned to FBP or IR. All studies were acquired with a 256-slice CT scanner. A coronary segment was considered interpretable if image quality was adequate for evaluation of coronary lesions in all segments ≥ 1.5 mm. The mean age was 56.3 ± 9.6 years and 165 (83%) were male, with no significant differences between groups. Most scans were acquired using prospective ECG triggering, without differences between groups (FBP 84% vs IR 82%; P = 0.71). A total of 3198 (94%) coronary segments were deemed of diagnostic quality. The percent assessable coronary segments was similar between groups (FBP 91.7% ± 4.0% vs IR 92.5% ± 2.8%; P = 0.12). Radiation dose was significantly lower in the IR group (2.8 ± 1.4 mSv vs 4.6 ± 3.0 mSv; P < 0.0001). Image noise (37.8 ± 1.4 HU vs 38.2 ± 2.4 HU; P = 0.20) and signal density (461.7 ± 51.9 HU vs 462.2 ± 51.2 HU; P = 0.54) levels did not differ between FBP and IR groups, respectively. The IR group was associated to significant effective dose reductions, irrespective of the acquisition mode. Application of IR in CTCA preserves image interpretability despite a significant reduction in radiation dose.

Evaluation of Right Ventricular Haemodynamics by Two-dimensional Strain in Patients with Chronic Pulmonary Thromboembolism

Background:Normal ranges for LVvolume index (LVVI) and LV mass index (LVMI) with echocardiography, cardiac CT and MRI are derived from measurements at end-diastole. CT angiography (CTA) image acquisition is usually performed with prospective ECG-triggering at a mid-diastolic phase (∼70% of R–R interval) when coronary artery motion is minimised. We compared twodimensional (2D)mid-diastolic (70%RR) and end diastolic CTAmeasurements of LV volume andmass indexwith 3D measurements at end diastole (ED). Methods: Twenty-five patients (age 60± 15 years, 36% female) who underwent full volume prospectively gated 320 slice CTAwere evaluated. LVMI and LVVI were calculated at ED using 3D software. Two-dimensional LVVI was calculated by the prolate ellipse method from the basal and mid LV at both 70%RRand ED. LV mass index was measured by Penn convention from the basal and mid LV at the same times. Results: LV volume index and LVMI derived from 2D measurements performed at ED from the basal LV significantly overestimate mass index and underestimate volume, but there is no significant difference in LVMI or LVVI derived from EDmid LV cavity measurements. Twodimensional calculations of LV volume at 70%RR from the basal and mid LV give a significantly smaller volume than end diastolic 3D, and the LVMI is overestimated by basal measurement, but there is no significant difference in LVMI when measured from the mid LV at 70%RR. Conclusion: LV mass index derived from 2D measurements is best done in the mid ventricle and is accurate at both end diastole and 70%RR when compared to end diastolic 3D. LV volume is significantly underestimated at 70%RR by 2Dmeasurements from both the basal andmid LV.

Radiation dose in coronary CT angiography associated with prospective ECG-triggering technique: comparisons with different CT generations

A retrospective analysis was performed in patients undergoing prospective ECG-triggered coronary computed tomography (CT) angiography (CCTA) with the single-source 64-slice CT (SSCT), dual-source 64-slice CT (DSCT), dual-source 128-slice CT and 320-slice CT with the aim of comparing the radiation dose associated with different CT generations. A total of 164 patients undergoing prospective ECG-triggered CCTA with different types of CT scanners were studied with the mean effective doses estimated at 6.8 ± 3.2, 4.2 ± 1.9, 4.1±0.6 and 3.8 ± 1.4 mSv corresponding to the 128-slice DSCT, 64-slice DSCT, 64-slice SSCT and 320-slice CT scanners. In this study a positive relationship was found between the effective dose and the body mass index (BMI). A low radiation dose is achieved in prospective ECG-triggered CCTA, regardless of the CT scanner generation. BMI is identified as the major factor that has a direct impact on the effective dose associated with prospective ECG-triggered CCTA.

Low dose dual-source CT angiography in infants with complex congenital heart disease: A randomized study

To investigate the radiation dose and image quality of prospective ECG-triggering dual-source CT angiography in infants with complex congenital heart disease (CHD) in comparison with retrospective ECG-gated scanning. Ninety-six infants less than 1 year old (60/36 male/female, age: 4.8 ± 2.7 months, weight: 5.8 ± 1.8 kg) with complex CHD were enrolled. Three image acquisition protocols were set: group 1: 80 kV, 100 mA, retrospective ECG-gated protocol; group 2: 80 kV, 100 mA, prospective ECG-triggering protocol with acquisition window of 380 ms; group 3: 80 kV, 100 mA, prospective ECG-triggering protocol with acquisition window of 200 ms. Patients were selected to any one of the protocols randomly. The signal-to-noise ratios (SNR) were calculated in the ascending aorta and the pulmonary artery trunk. Image quality was assessed by a five-point score. A score of <3 represents non-diagnostic. Effective radiation dose (ED) was calculated. Image quality score of groups 1, 2 and 3 were 4.1 ± 0.4, 4.0 ± 0.6 and 4.2 ± 0.6 (p = 0.224). SNR of ascending aorta and pulmonary artery trunk among them had no statistical difference (all p>0.05). The average ED (median) of groups 1, 2 and 3 were 1.17 ± 0.07 mSv (1.25 mSv), 0.72 ± 0.24 mSv (0.78 mSv) and 0.48 ± 0.41 mSv (0.39 mSv). Any two of the three groups had significant differences (all p<0.001). Prospective ECG-triggering DSCT angiography associated with a significantly lower ED than retrospective protocol, while maintaining image quality for diagnosis. Prospective ECG-triggering DSCT angiography could be used as a very important second-line diagnostic tool in infants with complex CHD.

Application of low-dose prospective electrocardiography-triggering dual-source CT angiography in infants and children with congenital heart disease

Objective To explore the application of low-dose prospective ECG-triggering dualsource CT (DSCT) angiography in infants and children with Kawasaki disease (KD).Methods Nineteen children diagnosed of Kawasaki disease underwent low-dose prospective ECG- triggering DSCT angiography (DSCTA) with free breathing and transthoracic echocardiogram (TTE).The overall imaging quality was graded on a five-point scale. Interobserver agreement in subjective image quality grading was assessed by Kappa statistics.The location,number and size of the aneurysms and dilations were recorded and compared with those of TTE.Pearson correlation analysis was used to evaluate the agreement on measurements between DSCTA and TTE.The average effective dose of DSCTA in all 19 children was calculated.Results DSCTA was performed successfully in all 19 children.A total of 91.5 ％ (226/247) segments permitted visualization with diagnostic image quality. Fifteen patients were diagnosed with coronary artery lesions. A total of 28 aneurysms and 15 arterial aneurysmal dilations were detected by DSCTA,while 19 aneurysms and 13 arterial aneurysmal dilations were found by TTE.TTE failed to detect 9 aneurysms (2 in the distal right coronary artery,2 in the posterior descending artery,1 in the middle of left anterior descending artery,1 in the middle of left circumflex artery,2 in the distal of LCX and 1 in the obtuse marginal branch)and 2 arterial aneurysmal dilations (1 at the diagonal branch and 1 at obtuse marginal branch). The concordance of DSCTA and TTE in measurement of diameter and length of these aneurysms and aneurysmal dilatations are good (0.63 ± 0.20) and (0.58 ± 0.20) cm vs ( 1.49 ± 0.83 ) and ( 1.22 ± 0.66) cm ( r =0.989 and 0.965,P ＜ 0.05 ).There was a good agreement on overall image quality ( Kappa =0.87 ). The mean effective dose was(0.24 ± 0.08) mSv.Conclusion Prospective ECG-triggering DSCTA with very low effective radiation dose is safe,reliable and more sensitive than TTE on diagnosing of coronary artery lesions,especially in the distal lesions,in infants and children with KD. Key words: Mucocutaneous lymph node syndrome; Coronary disease; Tomography, X-ray computed; Echocardiography ; Radiation dosage

Coronary CT angiography with prospective ECG-triggering: an effective alternative to invasive coronary angiography.

Despite the tremendous contributions of coronary CT angiography to coronary artery disease, radiation dose associated with coronary CT angiography has raised serious concerns in the literature, as the risk of developing radiation-induced malignancy is not negligible. Various dose-saving strategies have been implemented, with some of the strategies resulting in significant dose reduction. Of these strategies, prospective ECG-triggering is one of the most effective techniques with resultant effective radiation dose similar to or even lower than that of invasive coronary angiography. Prospective ECG-triggered coronary CT angiography has been reported to have high diagnostic accuracy in the diagnosis of coronary artery disease with image quality comparable to that of retrospective ECG-gating, but with significantly reduced radiation dose. Successful performance of prospective ECG-triggering is determined by strict exclusion criteria and careful patient preparation. The aim of this article is to provide an overview of the diagnostic applications of coronary CT angiography with prospective ECG-triggering with focus on radiation dose reduction. Radiation dose measurements are discussed with aim of allowing accurate dose estimation. Diagnostic value of prospective ECG-triggered coronary CT angiography in patients with different heart rate is discussed. Finally, current status and future directions are highlighted.

Evidence for prospective ECG-triggering coronary CT angiography in routine practice

Over the past decade, cardiac multidetector row CT (MDCT) has evolved, and the technology is poised to potentially alter the indications for diagnostic invasive coronary angiography (ICA) [1–10]. However, ionizing radiation concerns as related to increased cancer risks, initially applied to other organ systems [11, 12], have been translated to coronary CT angiography (CTA) and compared to ICA [13–17], while the dose dependent relation between low-radiation-dose exposure from cardiac procedures and subsequent risk of cancer has been reported [18]. Several strategies including ECG-triggered current modulation [19], lower tube voltage settings [13, 17, 20], and prospective ECG-triggering [21, 22] have progressively lowered patient radiation doses. One of the most applied approaches is prospective ECGtriggering [23, 24], where the exposure is confined to a predefined fraction of the time points of the cardiac cycle, rather than over the entire cycle. Depending on the details of the acquisition, the reduction in radiation dose can be as high as 80% [21, 22]. The effective dose of coronary CTA using prospective ECG-triggering (0.9–3.3 mSv) [2, 5] is comparable to, or lower than, diagnostic ICA (typical value of 7 mSv) [25]. However, there are unresolved concerns regarding diagnostic performance related to the limited phases of acquisition, and to date these methods have been most widely applied to patients with little risk of variations in cardiac cycle length and heart rates less than 70 beats per minute during the CT acquisition. In the current issue of the International Journal of Cardiovascular Imaging, Sun and Ng [26] performed a systematic review and meta-analysis of diagnostic value for coronary artery disease (CAD) using CTA with prospective ECG-triggering in comparison to ICA, and the authors also investigated the effective radiation dose. The 19 studies selected on primary selection criteria were reduced to fourteen that underwent the meta-analysis. Seven studies used singlesource 64-slice CT, four studies were performed with dual source 64-slice CT, two studies with 320-slice CT, and one with second generation of dual-source CT (128-slice). In 14 studies included in patient level (n = 910) analysis, pooled sensitivity for detection of significant CAD was 99% (95% CI: 98%, 100%) with specificity of 91% (95% CI: 88%, 94%) and the median negative predictive value (NPV) and positive predictive value (PPV) across studies were 94% (95% CI: 91%, 96%) and 99% (95% CI: 97%, 100%), respectively. Pooled positive (?LR) and negative (-LR) likelihood ratios were not reported at any of patient, vessel, or segment levels. Because observed heterogeneities were significant between 11 studies included in the vessel level (n = 3,531) and the segments level (n = 12,056) A. Salavati F. J. Rybicki (&) Applied Imaging Science Laboratory, Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, RA024, 75 Francis Street, Boston, MA 02115, USA e-mail: frybicki@partners.org

Prospective ECG triggering reduces prosthetic heart valve-induced artefacts compared with retrospective ECG gating on 256-slice CT

ObjectivesMultidetector computed tomography (MDCT) has diagnostic value for the evaluation of prosthetic heart valve (PHV) dysfunction but it is hampered by artefacts. We hypothesised that image acquisition using prospective triggering instead of retrospective gating would reduce artefacts related to pulsating PHV.MethodsIn a pulsatile in vitro model, a mono- and bileaflet PHV were imaged using 256 MDCT at 60, 75 and 90 beats per minute (BPM) with either retrospective gating (120 kV, 600 mAs, pitch 0.2, CTDIvol 39.8 mGy) or prospective triggering (120 kV, 200 mAs, CTDIvol 13.3 mGy). Two thresholds (>175 and <−45HU), derived from the density of surrounding structures, were used for quantification of hyper- and hypodense artefacts. Image noise and artefacts were compared between protocols.ResultsProspective triggering reduced hyperdense artefacts for both valves at every BPM (P = 0.001 all comparisons). Hypodense artefacts were reduced for the monoleaflet valve at 60 (P = 0.009), 75 (P = 0.016) and 90 BPM (P = 0.001), and for the bileaflet valves at 60 (P = 0.001), 90 (P = 0.001) but not at 75 BPM (P = 0.6). Prospective triggering reduced image noise at 60 (P = 0.001) and 75 (P < 0.03) but not at 90 BPM.ConclusionsCompared with retrospective gating, prospective triggering reduced most artefacts related to pulsating PHV in vitro.Key Points• Computed tomographic images are often degraded by prosthetic heart valve-induced artefacts • Prospective triggering reduces prosthetic heart valve-induced artefacts in vitro • Artefact reduction at 90 beats per minute occurs without image noise reduction • Prospective triggering may improve CT image quality of moving hyperdense structures

Initial experience on the application of 320-row CT angiography with low-dose prospective ECG-triggered in children with congenital heart disease

To investigate the clinical significance of the application of 320-row CT angiography with low-dose prospective ECG-triggered target scanning in children with complex congenital heart disease (CHD), and to compare with the results from transthoracic echocardiography (TTE). 22 patients (male 12 cases, female 10 cases, average age: 18 months, range: 14 days-9 years, average weight: 13 kg) received an examination through 320-row CT angiography with low-dose prospective ECG-triggered volume target scan mode and transthoracic echocardiography. The center of phase window for data collection in this study was set to 40% of the R-R interval. Of these, 18 patients received surgery and 4 patients received conventional cardiac angiography (CCA). The diagnostic accuracy of 320-row CTA was calculated according to the examination results from surgical and/or cardiac angiography. The overall quality score for CTA images was divided into five levels. The results were compared with the research data of radiation doses obtained from patients with congenital heart disease who had received CT angiography. Complex congenital heart disease was confirmed by surgical or CCA in each of 22 patients, with 42 cases of large vascular malformations outside the heart cavity, and 26 of intracardiac malformations. The diagnostic accuracy of 320-row CT angiography and transthoracic echocardiography for large vascular malformation outside the heart cavity was 95.2 and 80.9%, respectively; for intracardiac malformation the accuracy was 88.5 and 100.0%, respectively. There was significant difference between 320-row CT and transthoracic echocardiography in the diagnosis of large vascular malformation outside the heart cavity (P < 0.05) with better results in 320-row CT, and no significant difference was found in the diagnosis of intracardiac malformation (P > 0.05). The average subjective image quality score was 4.4 ± 0.7 points. The average effective dose was 0.42 ± 0.08 mSv. 320-row CT enables direct visualization of the vascular configuration and shape of the aorta, pulmonary artery, and other large vessels to diagnose extracardiac vascular malformations. Combined with transthoracic echocardiography, 320-row CT is a promising technology that may be able to replace catheter based angiography to evaluate congenital cardiovascular malformations.

Feasibility and diagnostic accuracy of a low radiation exposure protocol for prospective ECG-triggering coronary MDCT angiography

To compare the feasibility, accuracy, and effective radiation dose (ED) of multidetector computed tomography (MDCT) in the detection of coronary artery disease using a combined ED-saving strategy including prospective electrocardiogram (ECG) triggering with a short x-ray window and a body mass index (BMI)-adapted imaging protocol using adaptive statistical iterative reconstruction (ASIR; group 1), in comparison with a prospective ECG triggering strategy alone (group 2). One hundred and seventy patients scheduled for invasive coronary angiography (ICA) were evaluated. Fourteen patients were not eligible for MDCT. The remaining 156 patients were randomized to group 1 (78 patients) and group 2 (78 patients). Eight and 11 patients in groups 1 and 2, respectively, were excluded after randomization because the patients' heart rates were >65 beats/min. MDCT images were assessed for feasibility, signal-to-noise ration (SNR), and contrast-to-noise ratio (CNR), accuracy in detection of coronary stenoses >50% versus ICA and for ED. The feasibility, SNR, CNR, accuracy in a segment-based and patient-based model were similar in both groups (97 versus 95%, 14.5 ± 3.9 versus 14.2 ± 4.1, 16 ± 4.6 versus 16.5 ± 4.4, 95 versus 94% and 97 versus 99%, respectively). The ED in group 1 was 72% lower than in group 2 (2.1 ± 1.2 versus 7.5 ± 1.8 mSv, respectively; p<0.01). The use of a multi-parametric ED saving protocol results in a significant reduction in ED without a negative impact on accuracy.

Quantitative myocardial CT perfusion: a pictorial review and the current state of technology development

Coronary artery disease (CAD) is one of the leading causes of morbidity and mortality, and is associated with substantial and increasing resource burden. A combined physiologic and anatomic assessment may improve identification of patients with CAD who would benefit from revascularization and reduce unnecessary diagnostic and interventional procedures. Cardiovascular computed tomography (CT) has the potential to provide a comprehensive evaluation of CAD in a single setting. Although coronary CT angiography has been widely implemented for clinical use, the application of myocardial CT perfusion (CTP) has been relatively restricted because of a few limitations, such as beam hardening and the high radiation dose delivered. In this article, we first review the fundamental basis of the qualitative, semiquantitative, and quantitative techniques for myocardial CTP and discussed the strength and weakness of each approach. Beam-hardening correction for myocardial CTP with image-based method and dual-energy CT are then discussed with example cases demonstrating the effectiveness of each method. Initial experiences suggest both techniques can reduce beam-hardening artifact to a satisfactory extent. An overview on dose reduction technologies, such as prospective ECG triggering and iterative reconstruction for myocardial CTP, is also provided. Preclinical studies suggest it is feasible to perform low-dose quantitative myocardial CTP without affecting perfusion measurement. Finally, the impact of scan length on myocardial CTP is addressed.

Adenosine Stress High-Pitch 128-Slice Dual-Source Myocardial Computed Tomography Perfusion for Imaging of Reversible Myocardial Ischemia

Background— Coronary computed tomography angiography (CTA) enables accurate anatomic evaluation of coronary artery stenosis but lacks information about hemodynamic significance. The aim of this study was to evaluate 128-slice myocardial CT perfusion (CTP) imaging with adenosine stress using a high-pitch mode, in comparison with cardiac MRI (CMR). Methods and Results— Thirty-nine patients with intermediate to high coronary risk profile underwent adenosine stress 128-slice dual source CTP (128×0.6 mm, 0.28 seconds). Among those, 30 patients (64±10 years, 6% women) also underwent adenosine stress CMR (1.5T). The 2-step CTP protocol consisted of (1) adenosine stress-CTP using a high-pitch factor (3.4) ECG-synchronized spiral mode and (2) rest-CTP/coronary-CTA using either high-pitch (heart rate &lt;63 bpm) or prospective ECG-triggering (heart rate &gt;63 bpm). Results were compared with CMR and with invasive angiography in 25 patients. The performance of stress-CTP for detection of myocardial perfusion defects compared with CMR was sensitivity, 96%; specificity, 88%; positive predictive value (PPV), 93%; negative predictive value (NPV), 94% (per vessel); and sensitivity, 78%; specificity, 87%; PPV, 83%; NPV, 84% (per segment). The accuracy of stress-CTP for imaging of reversible ischemia compared with CMR was sensitivity, 95%; specificity, 96%; PPV, 95%; and NPV, 96% (per vessel). In 25 patients who underwent invasive angiography, the accuracy of CTA for detection of stenosis &gt;70% was (per segment): sensitivity, 96%; specificity, 88%; PPV, 67%; and NPV, 98.9%. The accuracy improved from 84% to 95% after adding stress CTP to CTA. Radiation exposure of the entire stress/rest CT protocol was only 2.5 mSv. Conclusions— Adenosine-induced stress 128-slice dual-source high-pitch myocardial CTP allows for simultaneously assessment of reversible myocardial ischemia and coronary stenosis, with good diagnostic accuracy as compared with CMR and invasive angiography, at a very low radiation exposure.

Image quality and radiation dose comparison of prospectively triggered low-dose CCTA: 128-slice dual-source high-pitch spiral versus 64-slice single-source sequential acquisition

Currently 64-multislice computed tomography (MSCT) scanners are the most widely used devices allowing low radiation dose coronary CT angiography (CCTA) with prospective ECG triggering. Latest 128-slice dual-source CT (DSCT) scanners offer prospective high-pitch spiral acquisition covering the heart during one single beat. We compared radiation dose and image quality from prospective 64-MSCT versus high-pitch spiral 128-slice DSCT scanning, as such data is lacking. CCTA of 50 consecutive patients undergoing 128-DSCT (2 × 64 × 0.6 mm collimation, 0.28 s rotation time, 3.4 pitch, 100-120 kV tube voltage and 320 mAs tube current-time product) were compared to CCTA of 50 heart rate (HR) and BMI matched patients undergoing 64-MSCT (64 × 0.625 mm collimation, 0.35 s rotation time, 100-120 kV tube voltage and 400-650 mA tube current). Image quality was rated on a 4-point scale by two independent cardiac imaging physicians (1 = excellent to 4 = non-diagnostic). Of 710 coronary segments assessed on 128-DSCT, 216 (30.4%) achieved an image quality score 1 excellent, 400 (56.3%) score 2, 76 (10.7%) score 3 and 18 (2.6%) score 4 (non-diagnostic). Of 737 coronary segments evaluated on 64-MSCT 271 (36.8%) had an image quality score of 1, 327 (44.4%) 2, 110 (14.9%) score 3, and 29 (3.9%) segments score 4. Average image quality score for both scanners was similar (P = 0.641). The mean heart rate during scanning was 58.7 ± 5.6 bpm on 128-DSCT and 59.0 ± 5.6 bpm on 64-MSCT, respectively. Mean effective radiation dose was 1.0 ± 0.2 mSv for 128-DSCT and 1.7 ± 0.6 mSv for 64-MSCT (P < 0.001). 128-DSCT with high-pitch spiral mode allows CCTA acquisition with reduced radiation dose at maintained image quality compared to 64-MSCT.

Dose reduction in 256-slice triple rule-out CT angiography

Abstract Objective Triple rule-out (TRO) computed tomographic angiography (CTA) is a protocol which allows evaluation of coronary arteries, aorta, pulmonary arteries and adjacent intrathoracic structures for patients with acute chest pain. Retrospective ECG-gated (RGH) is generally used for TRO CTA while the feasibility of using ECG-gated tube current modulation (ETCM) or prospective ECG-triggering (PGT) protocols have not been fully investigated. The objective of this study is to investigate the potential for dose reduction through the use of ETCM and PGT in TRO CTA examination as compared with routine RGH protocols. Material and methods All TRO CTA examinations were performed on a 256-slice CT scanner using an anthropomorphic phantom. To determine equivalent doses for different organs, thermal-luminance dosimeters (TLDs) were placed in different positions in the organs during the scanning and effective doses were calculated based on ICRP-103 guidelines. Effective doses calculated from volume CT dose index (CTDI vol ) were also compared with those obtained from TLD measurements. Results From the study, the mean effective dose for RGH, ETCM and PGT scanning was 21.54 mSv, 15.52 mSv and 10.75 mSv respectively. The doses for ETCM and PGT techniques were significantly reduced by 27% and 50% ( p Conclusion Radiation dose could be efficiently reduced by applying the ETCM and PGT protocols in the 256-slice TRO CTA examinations.

Commentary on: delayed enhancement imaging of myocardial viability: low-dose high-pitch CT versus MRI

In 2005, Nikolaou et al. [1] published a paper in EuropeanRadiology about the assessment of myocardial perfusionand viability from routine contrast-enhanced 16-detector-row computed tomography. The authors reported promisingresults, however, concluded carefully: “… application ofdelayed enhancement techniques might be useful. …However, this procedure requires a second delayed CTscan, increasing the radiation exposure of the patient.”I remember the first scientific presentations aboutcardiac perfusion imaging and delayed enhancement usingcomputed tomography—it was interesting, but the scientificcommunity considered this topic more or less a scientificgimmick rather than serious work with clinical relevance.Now, in 2011, Alkadhi et al. [2] publish in EuropeanRadiology a paper entitled “Delayed enhancement imagingof myocardial viability: Low-dose high-pitch CT versusMRI.” The authors included 24 patients and could showthat by using the newest generation CT equipment, delayedenhancement by CT has become a reality at a ultra-lowradiation dose in submillisievert range, and is now ready forclinical use: The estimated mean radiation dose was as lowas 0.89±0.07 mSv (range: 0.74–1.02 mSv). This lowradiation dose was obtained by using the “high-pitch”spiral CT technique with a pitch factor of 3.4 andprospective ECG-synchronization; furthermore a 100 kVtube voltage was applied for the delayed enhancement CTdata acquisition, making use of the higher attenuation ofiodine at lower photon energies. In the present study, theauthors perform a standard contrast-enhanced CTA using ahigh-pitch protocol on a commercially available 128-slice,dual-source CT system after the administration of 70 mliodinated contrast media. In order to achieve an adequatedose of iodine, 5 min after the first CT data–acquisition, asecond dose of 70 ml of iodinated contrast media wasadministered and, after a total delay of around 15 min fromthe first injection, a second high-pitch delayed enhancementCT data–set was obtained. The sensitivity, specificity, andaccuracy of CT for the diagnosis of non-viability were90.0%, 92.9%, and 91.7% per patient and 60.7%, 96.8%and 94.4% per segment, respectively, with MRI serving asthe gold standard.What happened in the last 6 years to make the vision ofmyocardial viability imaging a reality?In my opinion, new technical developments such as low-dose gating techniques, prospective ECG-triggering andhigh-pitch CT are all responsible for this present stepforward in cardiac imaging. The Cardiac Imaging ‘hype’started with the introduction of 64-slice CT with arevolution in image quality. This first wave of excitementwas followed by a disillusion: the radiation dose of cardiacCT reached values of 12–14 mSv, even higher than theradiation dose values of a conventional invasive angiog-raphy. However with the introduction of newer CTequipment with 128-, 256-, and 320-slices, as well asdual source CT–machines, faster CT protocols withradically lower radiation dose have become possible. Inthe present paper, the CTA–,data–acquisition, as well asthe delayed enhancement imaging, is performed using a highpitch of up to 3.4, compared with 0.2–0.4 for conventionalnormal retrospective ECG-triggered CT. Excellent imagequality with high pitch has become possible due to recentlyintroduced 128-dual-source CT technology. With this tech-nique, low-dose CT is possible, with a radiation dose lower

Diagnostic accuracy of dual-source CT coronary angiography with prospective electrocardiography triggering in patients with higher heart rate

Objective To evaluate the diagnostic accuracy of dual-source CT(DSCT)prospective ECG-triggering coronary angiography in patients with different heart rate(HR).Methods One hundred and three patients with suspected coronary artery disease underwent DSCT prospective ECG-triggered coronary angiography and invasive coronary angiography(ICA).The patients were grouped by HR during CT scans:low HR( 70 bpm,n=33).Image quality was scored using a 4-point scale.The sensitivity and specificity of DSCT in detecting≥50%stenosis were compared among subgroups where ICA was the gold standard.The differences were compared by using the X2 test of contingency on a per-segment and per-vessel basis.Results Image quality of 1580 coronary artery segments in 1648(95.9%)met the requirements for diagnosis.The image quality scores were(3.1±0.3),(3.1±0.3)and(3.0±0.4)point for subgroups(X2=2.80,P>0.05).Sensitivity and specificity were 82.8%(77/93)and 98.4%(428/435),88.3%(91/103)and 98.7%(442/448),and 80.3%(57/71)and 98.6%(424/430)for different subgroups(X2 were 0.69 and 0.13,all P>0.05).The overall area under the receiver operating characteristic(ROC)curve was 0.94(95%CI=0.92-0.96).The average effective radiation dose was(3.60±1.60)mSv.Conclusion DSCT coronary angiography with prospective ECG-triggering could be used for patients with high HR.And the diagnostic accuracy was not statistical significant between the patients with low HR and patients with medium to high HR. Key words: Heart rate; Coronary angiography; Tomography, X-ray computed; Diagnosis

Prognostic performance of low-dose coronary CT angiography with prospective ECG triggering

ObjectiveTo assess the prognostic value of low-dose 64-slice coronary CT angiography (CCTA) using prospective ECG triggering in a patient population with known or suspected coronary artery disease (CAD).DesignLongitudinal follow-up study.SettingTertiary...