Noninvasive coronary angiography with 16-detector row CT: effect of heart rate

64-Slice ECG-gated computed tomographic angiography for assessment of coronary arteries in brachycephalic dogs with pulmonary stenosis

BACKGROUND

Brachycephalic dogs with pulmonary stenosis are known to have a higher incidence of concurrent coronary artery abnormalities than non-brachycephalic breeds, which increases risk when performing balloon valvuloplasty. The use of ECG-gated CT angiography has been reported for the evaluation of coronary arteries in normal dogs and dogs with pulmonary stenosis. The purpose of this study was to report findings of coronary artery origination and morphology of main branches using ECG-gated CT angiography in brachycephalic dogs with pulmonary stenosis.

METHODS

An ECG-gated CT angiographic protocol was used to image coronary artery anatomy in nine brachycephalic dogs with pulmonary stenosis. Images were assessed for quality as well as coronary artery morphology by one veterinary radiologist, one veterinary cardiologist and one veterinary radiology resident.

RESULTS

All nine dogs had good to excellent image quality. Coronary artery anomalies were identified in three of nine dogs: one R2A anomaly, one L2A anomaly and one L2C anomaly. Two dogs were assessed to be poor balloon valvuloplasty candidates based on CT angiographic images.

LIMITATION

Coronary artery morphology was not confirmed via postmortem examination in all patients.

CONCLUSION

ECG-gated CT angiography is a minimally invasive imaging modality capable of diagnosing various coronary artery anomalies in brachycephalic dogs with pulmonary stenosis and aiding in the determination of patient candidacy for balloon valvuloplasty.

Efficacy and Safety of Iodixanol in Computed Coronary Tomographic Angiography and Cardiac Catheterization

Iodixanol is an iso-osmolar non-ionic dimeric hydrophilic contrast agent with a higher viscosity than the monomeric agents. It is the only Food and Drug Administration (FDA)-approved iso-osmolar agent in the United States, and it is the only contrast agent with an FDA-approved indication for use in cardiac computed tomographic angiography (CCTA), to assist in the diagnostic evaluation of patients with suspected coronary artery disease. In clinical studies, it has been noted to have fewer side effects and similar image quality when compared to low-osmolar contrast media. This can be attributed to the pharmacological properties of iodixanol. These contrast agents are used for coronary computed tomography angiography and cardiac catheterization. In this article, the use, tolerability, and efficacy of iodixanol are reviewed, specifically evaluating the use of CCTA and coronary angiography, including outcome studies, randomized trials, and comparisons to other contrast agents.

Deep learning-based motion correction algorithm for coronary CT angiography: Lowering the phase requirement for morphological and functional evaluation

PURPOSE

To investigate the performance of a deep learning-based motion correction algorithm (MCA) at various cardiac phases of coronary computed tomography angiography (CCTA), and determine the extent to which it may allow for reliable morphological and functional evaluation.

MATERIALS AND METHODS

The acquired image data of 53 CCTA cases, where the patient heart rate (HR) was ≥75 bpm, were reconstructed at 0, ±2, ±4, ±6, and ±8% deviations from each optimal systolic phase, with and without the MCA, yielding a total of 954 images (53 cases × 9 phases × 2 reconstructions). The overall image quality and diagnostic confidence were graded by two radiologists using a 5-point scale, with scores ≥3 being deemed clinically interpretable. Signal-to-noise ratio, contrast-to-noise ratio, vessel sharpness, and circularity were measured. The CCTA-derived fractional flow reserve (CT-FFR) was calculated in 38 vessels on 24 patients to identify functionally significant stenosis, using the invasive fractional flow reserve (FFR) as reference. All metrics were compared between two reconstructions at various phases.

RESULTS

Inferior image quality was observed as the phase deviation was enlarged. However, MCA significantly improved the image quality at nonoptimal phases and the optimal phase. Coronary artery evaluation was feasible within 4% phase deviation using MCA, with interpretable overall image quality and high diagnostic confidence. With MCA, the performance of identifying functionally significant stenosis via CT-FFR was increased for images at various phase deviations. However, obvious decrease in accuracy, as compared to the image at the optimal phase, was found on those with deviations >4%.

CONCLUSION

The deep learning-based MCA allows up to 4% phase deviation in acquiring CCTA for reliable morphological and functional evaluation on patients with high HRs.

Detector-trigger-based cardiac multiphase micro-CT imaging for small animals

BACKGROUND

Micro-computed tomography is important in cardiac imaging for preclinical small animal models, but motion artifacts may appear due to the rapid heart rates. To avoid influence of motion artifacts, the prospective ECG gating schemes based on an X-ray source trigger have been investigated. However, due to the lack of pulsed X-ray exposure modes, high-resolution micro-focus X-ray sources do not support source triggering in most cases.

OBJECTIVE

To develop a fast-cardiac multiphase acquisition strategy using prospective ECG gating for micro-focus X-ray tubes with a continuous emission mode.

METHODS

The proposed detector-trigger-based prospective ECG gating acquisition scheme (DTB-PG) triggers the X-ray detector at the R peak of ECG, and then collects multiple phase projections of the heart in one ECG cycle by sequence acquisition. Cardiac multiphase images are reconstructed after performing the same acquisition in all views. The feasibility of this strategy was verified in multiphase imaging experiments of a phantom with 150 ms motion period and a mouse heart on a micro-focus micro-CT system with continuous emission mode.

RESULTS

Using a high frame-rate CMOS detector, DTB-PG discriminates the positions of the motion phantom well in 10 different phases and enables to distinguish the changes in the cardiac volume of the mouse in different phases. The acquisition rate of DTB-PG is much faster than other prospective gating schemes as demonstrated by theoretical analysis.

CONCLUSIONS

DTB-PG combines the advantages of prospective ECG gating strategies and X-ray detector-trigger mode to suppress motion artifacts, achieve ultra-fast acquisition rates, and relax hardware limitations.

Radiation dose reduction method combining the ECG-Edit function and high helical pitch in retrospectively-gated CT angiography

INTRODUCTION

The purpose of this study was to demonstrate that dose reduction does not compromise image quality when combining high helical pitch (HP) and the ECG-Edit function during low HP retrospectively gated computed tomography angiography (CTA).

METHODS

This study made use of a pulsating cardiac phantom (ALPHA 1 VTPC). The heart rate (HR) of the cardiac phantom was changed in five intervals, every 5 beats per minute (bpm), from 40 to 60 bpm. Evaluation of a range of HR was important because data loss might occur when combining a low HR and high HP. We performed retrospectively gated CTA scans five times using a low HP (0.16) and high HP (0.24), for each of the five HR intervals, using a 64-detector row CT scanner. The CT volume dose index (CTDI_vol) was recorded from the CT console of each scan. For the images with data loss, data were repaired using the ECG-Edit function. We compared the CTDI_vol, estimated cardiac phantom volume, and the visualization of the coronary ladder phantom between HP 0.16, with or without repaired HP 0.24, using the ECG-Edit function.

RESULTS

Data loss occurred with a HR of 40 bpm and 45 bpm when using HP 0.24. The CTDI_vol was reduced by approximately 33% with HP 0.24 when compared with HP 0.16. There were no significant differences in the mean cardiac motion phantom volume and visualization scores between HP 0.16 and with and without repaired HP 0.24 using the ECG-Edit function (p < 0.05).

CONCLUSION

The ECG-Edit function is potential useful for repairing the lost data in patients with a low HR, and when combined with a high HP, it is possible to reduce the radiation dose by approximately 33%.

IMPLICATIONS FOR PRACTICE

The ECG-Edit function and high HP may be a viable option in pediatric CTA studies.

Selection of optimal cardiac phases for ECG-triggered coronary CT angiography in pediatrics

PURPOSE

The use of coronary computed tomography angiography (CCTA) in children remains limited by patient's irradiation, and motion artefacts impairing image quality. Triggering the acquisition at the appropriate moment, and acquiring only necessary components of the cardiac cycle could overcome these limitations. Yet, optimal cardiac intervals to perform CCTA as a function of heart rate (HR) have not yet been addressed in pediatrics.

METHODS

Fifty children with coronary artery anomalies underwent a CCTA on a wide-coverage single-beat CT scanner. Multiple phases from 25% to 85% of the R-R interval were acquired and reconstructed with 10% increments. Two radiologists independently assessed motion artifacts on each cardiac phase using a 4-point semi-quantitative scale.

RESULTS

At patient level, the best phase for acquisition was found in diastole for patients with HR ≤ 75 bpm and in systole for patients with HR > 85 bpm. At coronary segments and structures level, median optimal phases were reported at 70%, 80%, 47%, 50%, and 54% of the R-R interval for patients with HR ≤ 60, 61-75, 86-100, 101-130, and >130 bpm respectively. For patients with HR between 76 and 85 bpm, no clear trend could be observed. Optimal acquisition durations represented 10% (2 phases), 20% (3 phases), 50% (multiphase), 20% (3 phases), and 10% (2 phases) of the R-R interval for patients with HR ≤ 60, 61-75, 76-100, 101-130, and >130 bpm, respectively.

CONCLUSIONS

Optimal positioning and duration of CCTA acquisition intervals were investigated as a function of children's HR, to reduce motion artifacts and patient's irradiation.

Predictors of abnormality in thallium myocardial perfusion scans for type 2 diabetes

Type 2 diabetes mellitus (T2DM) increases coronary artery disease (CAD) risk. In this study, we used T2DM clinical variables to predict abnormality in thallium-201 myocardial perfusion scans (Th-201 scans). These clinical variables were summed stress score (SSS), summed rest score, and summed difference score (SDS), with data obtained from 368 male and 428 female participants with T2DM. Multiple linear regression results were as follows. In male participants, body mass index (BMI) and creatinine (Cr) were associated with SSS (β = 0.224, p < 0.001; β = 0.140, p = 0.022, respectively), and only BMI was associated with SDS (β = 0.174, p = 0.004). In female participants, BMI and high-density lipoprotein cholesterol level were associated with SSS (β = 0.240, p < 0.001; β =  - 0.120, p = 0.048, respectively), and only BMI was correlated with SDS (β = 0.123, p = 0.031). Our multivariate logistic regression indicated that in male and female participants, BMI was the only independent indicator of high SSS (SSS ≥ 9). In this study, we demonstrated that male patients have a higher SSS and SDS than female patients do in Th-201 scans for T2DM in a Chinese population. For male and female patients, BMI was the strongest predictor of abnormality in Th-201 scans. Our results can help clinicians identify patients with T2DM at high risk of CAD.

Low-Dose Coronary CT Angiography in Patients with Atrial Fibrillation: Comparison of Image Quality and Radiation Exposure with Two Different Approaches

RATIONALE AND OBJECTIVES

To evaluate image quality, coronary interpretability and radiation exposure of coronary CT angiography (CCTA) performed in patients with atrial fibrillation (AF) with the latest scanner generation, comparing two different technical approaches. A new scanner that combines a 0.23 mm spatial resolution, a new generation of iterative reconstruction, fast gantry rotation time and the intracycle motion-correction algorithm to improve the temporal resolution was recently introduced in the clinical field.

MATERIALS AND METHODS

We enrolled 105 consecutive patients with chronic AF who performed CCTA with a whole-heart coverage high-definition CT scanner (16-cm z-axis coverage with 256 detector rows, 0.28 s gantry rotation time). Five of them were excluded for impaired renal function. Patients were randomized between a double acquisition protocol (50 patients, group 1) or a single acquisition protocol (50 patients, group 2). The image quality, coronary segment interpretability and effective dose (ED) of CCTA were assessed.

RESULTS

The mean HR during the scan was 85.6±21 bpm in group 1 vs. 83.7±23 bpm in Group 2, respectively (p < ns). In group 2, overall image quality was high and comparable with that of group 1 (Likert scale =3.2 ± 1.4 vs. 3.3 ± 1.2, p = ns, in group 1 and 2, respectively). Coronary interpretability was high and similar between the two groups (97.5% and 97.1% in group 1 and 2, p = ns, respectively). Mean ED was significantly higher in group 1 than in group 2 (5.3 ± 1.8 mSv vs. 2.7 ± 0.7 mSv, p < 0.001).

CONCLUSION

The novel whole-heart coverage CT scanner allows to perform CCTA with a single-acquisition protocol with high image quality and low radiation exposure in AF patients.

Effect of bolus tracking region-of-interest position within the descending aorta on luminal enhancement of coronary arteries in coronary computed tomography angiography

To compare coronary artery luminal enhancement in coronary computed tomography angiography (CCTA) between ventral and dorsal region-of-interest (ROI) bolus tracking in the descending aorta.The records of 165 consecutive patients who underwent CCTA with non-helical acquisition from July 2017 to March 2018 were retrospectively examined. We performed 320-row CCTA with bolus tracking [scan triggered at 260 HU in the descending aorta] and 133 patients were finally included. ROI was set in the ventral and dorsal halves of the descending aorta in 68 and 65 patients, respectively.Contrast arrival time was significantly shorter in the dorsal group (ventral: 21.8 ± 0.372 s; dorsal: 20.7 ± 0.369; P = .0295). The mean density of the proximal and distal RCA was significantly higher in the ventral group (proximal: ventral, 428.1 ± 6.95 HU; dorsal, 405.5 ± 7.72 HU, P = .0318; distal: ventral, 418.0 ± 9.29 HU; dorsal, 393.2 ± 9.46 HU, P = .0133).Dorsal bolus tracking ROI in the descending thoracic aorta significantly reduced preparation time and RCA CT values.

Incidental myocardial perfusion defect detected on ECG-gated CT aortogram

We report the case of a 49-year-old man with a history of diabetes and hypertension who presented to the emergency room with intermittent chest pain radiating to the back for one day. An electrocardiogram-gated CT aortogram excluded the emergency department's primary consideration of aortic dissection, but incidentally revealed a myocardial perfusion defect and corresponding coronary artery stenosis. Cardiac catheterization performed the following day confirmed the CT findings and the patient underwent angioplasty and stent placement. We show that despite a different protocol than coronary CTA or myocardial perfusion CT, a gated CTA for dissection (CT aortogram) is capable of detecting resting perfusion abnormalities in patients presenting to the emergency room with chest pain.

Influence of Heart Rate and Innovative Motion-Correction Algorithm on Coronary Artery Image Quality and Measurement Accuracy Using 256-Detector Row Computed Tomography Scanner: Phantom Study

Objective

To investigate the efficacy of motion-correction algorithm (MCA) in improving coronary artery image quality and measurement accuracy using an anthropomorphic dynamic heart phantom and 256-detector row computed tomography (CT) scanner.

Materials and Methods

An anthropomorphic dynamic heart phantom was scanned under a static condition and under heart rate (HR) simulation of 50–120 beats per minute (bpm), and the obtained images were reconstructed using conventional algorithm (CA) and MCA. We compared the subjective image quality of coronary arteries using a four-point scale (1, excellent; 2, good; 3, fair; 4, poor) and measurement accuracy using measurement errors of the minimal luminal diameter (MLD) and minimal luminal area (MLA).

Results

Compared with CA, MCA significantly improved the subjective image quality at HRs of 110 bpm (1.3 ± 0.3 vs. 1.9 ± 0.8, p = 0.003) and 120 bpm (1.7 ± 0.7 vs. 2.3 ± 0.6, p = 0.006). The measurement error of MLD significantly decreased on using MCA at 110 bpm (11.7 ± 5.9% vs. 18.4 ± 9.4%, p = 0.013) and 120 bpm (10.0 ± 7.3% vs. 25.0 ± 16.5%, p = 0.013). The measurement error of the MLA was also reduced using MCA at 110 bpm (19.2 ± 28.1% vs. 26.4 ± 21.6%, p = 0.028) and 120 bpm (17.9 ± 17.7% vs. 34.8 ± 19.6%, p = 0.018).

Conclusion

Motion-correction algorithm can improve the coronary artery image quality and measurement accuracy at a high HR using an anthropomorphic dynamic heart phantom and 256-detector row CT scanner.

The Value of 16-cm Wide-Detector Computed Tomography in Coronary Computed Tomography Angiography for Patients With High Heart Rate Variability

OBJECTIVE

The aim of this study was to investigate radiation dose and image quality of coronary computed tomography (CT) angiography (CCTA) for patients with high heart rate variability (HRv) using 16-cm wide-detector CT scanner.

METHODS

One hundred sixty-six patients with uncontrolled heart rate underwent CCTA on a 16-cm wide-detector CT system and were divided into 2 groups based on their HRv for analysis: group A (n = 95, HRv ≤10 beats/min [bpm]) and group B (n = 71, HRv >10 bpm). Images in both groups were reconstructed with motion correction algorithm. Subjective and objective image qualities were analyzed.

RESULTS

There were no significant differences in age, body mass index, and heart rate (68.1 ± 11.4 vs 67.6 ± 12.3 bpm) between the 2 groups (P > 0.05). However, group B had significantly higher HRv than group A (33.5 ± 24.4 vs 7.8 ± 1.2 bpm, P < 0.001). All images were acceptable for clinical diagnosis. Compared with group A, image quality scores in group B decreased slightly (4.1 ± 0.5 vs 4.0 ± 0.6). However, the difference was not statistically significant. The mean effective doses were both relatively low at 2.2 ± 1.1 mSv in group A and 2.6 ± 1.4 mSv in group B.

CONCLUSIONS

Single-heartbeat free-breathing CCTA can be performed for patients with high HRv using 16-cm wide-detector CT scanner to achieve diagnostic image quality with low radiation dose.

Automated determination of cardiac rest period on whole-heart coronary magnetic resonance angiography by extracting high-speed motion of coronary arteries

PURPOSE

The aim of the present study was to develop an automated system for determining the cardiac rest period during whole-heart coronary magnetic resonance angiography (CMRA) examination.

MATERIALS AND METHODS

Ten healthy male volunteers (25-51 years old, 50-77 beats/min heart rate) were enrolled in this prospective study. A motion area map was generated from a cine image set by extracting high-speed component of cardiac motion, and it was used to specify the rest period in the proposed CMRA. In conventional CMRA, the rest period was determined based on the visual inspection of cine images. Agreement of the start time, end time, and trigger time between the two methods was assessed by the Bland-Altman plot analysis. Two observers visually evaluated the quality of the curved planar reformation (CPR) image of the coronary arteries.

RESULTS

The proposed method significantly prolonged the start time (mean systematic difference 37.7 ms, P < 0.05) compared with the conventional method. Good agreement was observed for the end time (mean systematic difference 8.9 ms) and trigger time (mean systematic difference -28.8 ms) between the two methods. A significantly higher image quality (P < 0.05) was provided for the left circumflex artery in the proposed CMRA (mean grading score 3.88) than in conventional CMRA (mean grading score 3.68).

CONCLUSION

Our system enabled detection of the rest period automatically without operator intervention and demonstrated somewhat higher image quality compared with conventional CMRA. Its use may be useful to improve the imaging workflow for CMRA in clinical practice.

Diagnostic Performance of a Novel Coronary CT Angiography Algorithm: Prospective Multicenter Validation of an Intracycle CT Motion Correction Algorithm for Diagnostic Accuracy

OBJECTIVE

Motion artifact can reduce the diagnostic accuracy of coronary CT angiography (CCTA) for coronary artery disease (CAD). The purpose of this study was to compare the diagnostic performance of an algorithm dedicated to correcting coronary motion artifact with the performance of standard reconstruction methods in a prospective international multicenter study.

SUBJECTS AND METHODS

Patients referred for clinically indicated invasive coronary angiography (ICA) for suspected CAD prospectively underwent an investigational CCTA examination free from heart rate-lowering medications before they underwent ICA. Blinded core laboratory interpretations of motion-corrected and standard reconstructions for obstructive CAD (≥ 50% stenosis) were compared with ICA findings. Segments unevaluable owing to artifact were considered obstructive. The primary endpoint was per-subject diagnostic accuracy of the intracycle motion correction algorithm for obstructive CAD found at ICA.

RESULTS

Among 230 patients who underwent CCTA with the motion correction algorithm and standard reconstruction, 92 (40.0%) had obstructive CAD on the basis of ICA findings. At a mean heart rate of 68.0 ± 11.7 beats/min, the motion correction algorithm reduced the number of nondiagnostic scans compared with standard reconstruction (20.4% vs 34.8%; p < 0.001). Diagnostic accuracy for obstructive CAD with the motion correction algorithm (62%; 95% CI, 56-68%) was not significantly different from that of standard reconstruction on a per-subject basis (59%; 95% CI, 53-66%; p = 0.28) but was superior on a per-vessel basis: 77% (95% CI, 74-80%) versus 72% (95% CI, 69-75%) (p = 0.02). The motion correction algorithm was superior in subgroups of patients with severely obstructive (≥ 70%) stenosis, heart rate ≥ 70 beats/min, and vessels in the atrioventricular groove.

CONCLUSION

The motion correction algorithm studied reduces artifacts and improves diagnostic performance for obstructive CAD on a per-vessel basis and in selected subgroups on a per-subject basis.

The incremental clinical value of cardiac hybrid SPECT/CTA imaging in coronary artery disease

Coronary artery disease (CAD) is a major cause of death worldwide. It is significantly important to assess the coronary lesion and its pathophysiological relevance comprehensively. Coronary computed tomography angiography (CTA) or myocardial perfusion imaging alone suffers from some limitations in the evaluation of CAD. Through the integration and spatial colocalization of complementary morphological and functional information, the results of published hybrid single-photon emission computed tomography (SPECT)/CTA studies in patients with CAD are promising for detecting functionally relevant coronary artery lesion and evaluating the relationship between diseased coronary artery, coronary artery anomaly, myocardial bridging, or coronary calcification and myocardial ischemia. Compared with other diagnostic procedures, such as CTA, myocardial perfusion imaging alone, and side-by-side SPECT-CTA analysis, SPECT/CTA imaging has incremental value in the evaluation of CAD. Hybrid SPECT/CTA imaging can provide the physicians with more clinical evidence that helps with the treatment strategy decision-making process, thus acting as a gatekeeper to reduce unnecessary invasive examinations and revascularization procedures. In addition, follow-up SPECT/CTA fusion imaging plays a role in predicting prognosis by displaying clearly the relationship between postoperative vessel and myocardial blood supply. However, several limitations should be considered, including the increased radiation exposure, the limited number of patients, and the lack of a uniform gold standard. More data are needed to better specify the role of hybrid SPECT/CTA imaging in the management of CAD.

Image Quality, Overall Evaluability, and Effective Radiation Dose of Coronary Computed Tomography Angiography With Prospective Electrocardiographic Triggering Plus Intracycle Motion Correction Algorithm in Patients With a Heart Rate Over 65 Beats Per Minute

PURPOSE

Recently, a new intracycle motion correction algorithm (MCA) was introduced to reduce motion artifacts from heart rate (HR) in coronary computed tomography angiography (cCTA). The aim of the study was to evaluate the image quality, overall evaluability, and effective radiation dose (ED) of cCTA with prospective electrocardiographic (ECG) triggering plus MCA as compared with standard protocol with retrospective ECG triggering in patients with HR≥65 bpm.

MATERIALS AND METHODS

One hundred consecutive patients (67±10 y) scheduled for cCTA with 65<HR<80 bpm were retrospectively analyzed. The patients were assigned to 2 groups undergoing prospective (group 1) or retrospective (group 2) triggered cCTA. The study protocol was approved by the Institutional Ethics Committee and a written informed consent was obtained from all patients. Image noise, signal to noise ratio, contrast to noise ratio, Likert image quality score (score 1, nondiagnostic; score 2, adequate; score 3, good; score 4, excellent), overall image evaluability, and ED were measured and compared between the 2 groups. Both vessel-based and patient-based analyses were evaluated. Student test or Wilcoxon test were used to evaluate differences of continuous variables, whereas the χ test was used to study differences with regard to categorical data. A P-value <0.05 was considered statistically significant.

RESULTS

cCTA was successfully performed in all patients. In a segment-based model, group 1 compared with group 2 showed a lower rate of overall artifacts (67% vs. 83%; P<0.001) and motion artifacts (49% vs. 66%; P<0.001), resulting in a better Likert image quality score (2.83±1.03 vs. 2.37±1.02; P<0.01) and overall evaluability (85% vs. 75%; P<0.01). Group 1 showed a lower ED as compared with group 2 (3.1±1.9 vs. 11.9±3.3 mSv; P<0.01).

CONCLUSION

MCA and cCTA with prospective ECG-triggering acquisition in patients with high HR improves image quality and overall evaluability compared with cCTA with standard retrospective ECG triggering.

Reduction of Coronary Motion Artifacts in Prospectively Electrocardiography-Gated Coronary Computed Tomography Angiography Using Monochromatic Imaging at Various Energy Levels in Combination With a Motion Correction Algorithm on Single-Source Fast Tube Voltage Switching Dual-Energy Computed Tomography: A Phantom Experiment

OBJECTIVES

The aim of this study was to assess the effect of monochromatic imaging at various energy levels in combination with a motion correction algorithm (MCA) in single-source dual-energy coronary computed tomography angiography (CCTA) with fast switching of tube voltage on the reduction of coronary motion artifacts (CMA) in a phantom setting.

MATERIALS AND METHODS

Using this dual-energy computed tomography technique with a phantom comprising models of coronary vessels filled with contrast medium and pulsating at constant heart rates of 60 to 100 beats per minute, we reconstructed monochromatic images of CCTA obtained at 50 to 90 keV with and without use of MCA. Cardiac motion was modeled by simulating the in vivo time-volume curve of the left ventricle. Two independent readers graded CMA in 9 coronary segments using a 5-point scale (1, poor; 3 to 5, interpretable; 5, excellent). At each heart rate, we compared the average score of CMA between images obtained at 50 to 90 keV with and without use of MCA using Wilcoxon signed rank test, and we compared the score among images obtained at 50 to 90 keV with use of MCA using Kruskal-Wallis and post hoc tests. We also compared the percentages of image interpretability and improvement in image interpretability among images obtained at 50 to 90 keV with use of MCA.

RESULTS

With the use of MCA, the average score of CMA was significantly higher for images obtained at each energy level from 50 to 70 keV (P < 0.05) and was comparable at 80 and 90 keV, and it was comparable among those obtained at 50 to 70 keV. With its use, the percentages of image interpretability were similarly high at 50 to 70 keV at 60 to 80 beats per minute (78%-100%), and they were higher at 50 to 60 keV (72%-83%) than at 70 keV at 90 to 100 beats per minute (50%-56%). The percentages of improved image interpretability with MCA were similarly high at 50 to 70 keV at 60 to 80 beats per minute (56%-100%), and they were higher at 50 to 60 keV (62%-77%) than at 70 keV at 90 to 100 beats per minute (36%-43%). The percentages of image interpretability and improved image interpretability with MCA were insufficient at 80 and 90 keV.

CONCLUSIONS

Coronary motion artifacts were significantly reduced in images of monochromatic CCTA obtained at 50 to 70 keV in combination with MCA compared with those obtained without MCA, and the percentages of image interpretability and improved image interpretability with use of MCA were relatively high at 50 to 70 keV, and particularly at 50 to 60 keV, even at 90 to 100 beats per minute.

Coronary Computed Tomography Angiography in Combination with Coronary Artery Calcium Scoring for the Preoperative Cardiac Evaluation of Liver Transplant Recipients

Liver transplantation is the best treatment option for early-stage hepatocellular carcinoma, liver cirrhosis, fulminant liver failure, and end-stage liver diseases. Even though advances in surgical techniques and perioperative care have improved postoperative outcomes, perioperative cardiovascular complications are a leading cause of postoperative morbidity and mortality following liver transplantation. Ischemic coronary artery disease (CAD) and cardiomyopathy are the most common cardiovascular diseases and could be negative predictors of postoperative outcomes in liver transplant recipients. Therefore, comprehensive cardiovascular evaluations are required to assess perioperative risks and prevent concomitant cardiovascular complications that would preclude good outcomes in liver transplant recipients. The two major types of cardiac computed tomography are the coronary artery calcium score (CACS) and coronary computed tomography angiography (CCTA). CCTA in combination with the CACS is a validated noninvasive alternative to coronary angiography for diagnosing and grading the severity of CAD. A CACS > 400 is associated with significant CAD and a known important predictor of posttransplant cardiovascular complications in liver transplant recipients. In this review article, we discuss the usefulness, advantages, and disadvantages of CCTA combined with CACS as a noninvasive diagnostic tool for preoperative cardiac evaluation and for maximizing the perioperative outcomes of liver transplant recipients.

The influence of cardiac function on coronary arterial enhancement at coronary computed tomography angiography: A cross-sectional study

Background:

The purpose of this study was to evaluate the influence of ejection fraction (EF) on peak aortic time (PAT) and peak aortic enhancement (PAE) during coronary computed tomography angiography (CTA).

Materials and Methods:

One-hundred and twenty patients (64 men, 56 women) underwent measurement of coronary CTA with a measurement of EF within 3 months of coronary CTA. Pearson's correlation coefficient analysis was used to investigate the relationships between EF, PAT and PAE, and peak attenuation of all coronary arteries.

Results:

The range of EF was (25%–70%) (mean: 55 ± 7.7). The range of PAT and PAE of ascending aorta on bolus test was 13–31 s (mean: 19.3 ± 2) and 153–435 HU (mean: 235 ± 40.6), respectively. Mean peak attenuation of ascending aorta, right coronary artery, left coronary artery, left circumflex artery, and left anterior descending were (561 ± 119), (476 ± 109), (505 ± 108), (467 ± 113), and (473 ± 104), respectively. There was a negative correlation between EF and PAT (r = −0.266, P = 0.003); however, there was no significant correlation between EF and PAE (r = −0.027, P = 0.767). In addition, there was no significant correlation between EF and the peak attenuation of coronary arteries.

Conclusion:

PAT was related to EF, but there was no relationship between PAE and EF. One of the explanation is that the left ventricular EF used for our study was assessed with echocardiography which is used roughly estimation of EF with interval of 5%–10% and may cause confounding results.

Bailout intravenous esmolol for heart rate control in cardiac computed tomography angiography

OBJECTIVE

To evaluate the efficacy and safety of a heart rate (HR) reduction protocol using intravenous esmolol as bailout for failed oral metoprolol regimens in patients undergoing coronary computed tomography angiography (CCTA) with 64-slice multidetector computed tomography (64-MDCT).

METHODS

Patients who underwent cardiac 64-MDCT in a single institution between 2011 and 2014 were analyzed. Those with HR above 60 beats per minute (bpm) on presentation received oral metoprolol (50-200 mg) at least one hour before CCTA. Intravenous esmolol 1-2 mg/kg was administered as a bolus whenever HR remained over 65 bpm just before imaging. The primary efficacy endpoint was HR <65 bpm during CCTA. The primary safety endpoint was symptomatic hypotension or bradycardia up to hospital discharge.

RESULTS

During the study period CCTA was performed in 947 cases. In 86% of these, oral metoprolol was the only medication required to successfully reduce HR <60 bpm. Esmolol was used in the remaining 130 patients (14%). For esmolol-treated patients mean baseline and acquisition HR were 74±14 bpm and 63±9 bpm, respectively (p<0.001). The target HR of <65 bpm was achieved in 82 of the 130 esmolol-treated patients (63%). Considering the whole population, esmolol use led to a significant increase in the primary efficacy endpoint from 86% to 95% (p<0.001). Esmolol also resulted in a statistically, but not clinically, significant reduction in systolic blood pressure (144±22 to 115±17 mmHg; p<0.001). The combined primary safety endpoint was only observed in two (1.5%) patients.

CONCLUSION

Despite optimal use of oral beta-blockers, 14% of patients needed intravenous esmolol for HR control. The pre-medication combination of oral metoprolol and on-demand administration of intravenous esmolol was safe and effective and enabled 95% of patients to be imaged with HR below 65 bpm.

Impact of a motion correction algorithm on image quality in patients undergoing CT angiography: A randomized controlled trial

AIMS

To investigate the motion correction algorithm Snapshot-Freeze (SSF) compared to standard reconstruction (STD) in patients randomized to receive beta-blockers (BB) or no beta-blockers (non-BB) before coronary CT, and to investigate if SSF can replace BB.

METHODS

One hundred and forty patients scheduled for coronary CT were randomized. All images were reconstructed by the SSF and STD algorithms. Image quality was evaluated according to Likert score (1: excellent, 2: good, 3: adequate, 4: non-diagnostic) and presence of artifacts was noted.

RESULTS

Images from 64 patients in the BB group (mean HR 56±4bpm) and 51 patients in the non-BB group (mean HR 67±7bpm) were analyzed. Twenty five patients were excluded because of tachycardia, bradycardia or reconstruction errors in SSF. SSF increased the number of excellent images in both groups compared to the STD algorithm (BB: 59% vs.44%; non-BB: 25% vs. 8%), but the number of non-diagnostic images was not significantly reduced. SSF reduced motion artifacts (BB: 11% vs. 31%; non-BB: 49% vs. 75%), but despite this reduction, motion artifacts in non-BB were still more frequent compared to the BB group analyzed by STD (49% vs. 31%).

CONCLUSION

SSF improves image quality and reduces motion artifacts, but does not compensate for the absence of BB.

Diagnostic Accuracy, Image Quality, and Patient Comfort for Coronary CT Angiography Performed Using Iso-Osmolar versus Low-Osmolar Iodinated Contrast: A Prospective International Multicenter Randomized Controlled Trial

RATIONALE AND OBJECTIVES

The impact of iso-osmolar versus low-osmolar iodinated contrast on diagnostic accuracy for coronary computed tomography angiography (CCTA), against the reference standard of invasive coronary angiography (ICA), has not been determined. We sought to compare in an international multicenter randomized controlled trial the impact of iso-osmolar iodixanol versus low-osmolar iopamidol on diagnostic accuracy, image quality, patient symptoms, and heart rate variability.

MATERIALS AND METHODS

Adult patients who were clinically referred for ICA were randomly assigned to receive either iodixanol (n = 133) or iopamidol (n = 133) with an investigational CCTA. CCTA stenosis and image quality were scored by consensus of independent blinded core laboratory readers. Degree of stenosis by ICA was evaluated using quantitative coronary angiography and used to calculate diagnostic accuracy. Heart rate variability and patient-reported symptom questionnaires were compared between the two groups.

RESULTS

A total of 266 subjects underwent both CCTA and ICA (57 ± 11 years, 58% male). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for detecting coronary artery disease were 86.8%, 93.7%, 84.6%, 94.7%, and 91.7% for iodixanol and 94.7%, 88.4%, 76.6%, 97.7%, and 90.2% for iopamidol, respectively, on a per-patient level. These values were not significantly different between the two groups. There was no significant difference in image quality and heart rate increase or variability. The majority of patients reported symptoms (59.4%), with no differences in the overall or individual rate of any or moderate to severe symptoms between the two groups. Patients receiving iodixanol reported lower incidence of moderate to severe flushing (3.0% vs. 12.8%, P = .005). Lower rates of moderate to severe symptoms were particularly evident for patients with ≥55 years receiving iodixanol versus iopamidol (8.5% vs. 24.6%, P = .01).

CONCLUSIONS

Diagnostic performance and image quality were similar for CCTA performed with iso-osmolar versus low-osmolar iodinated contrast. Indices of patient comfort were improved with iso-osmolar iodinated contrast.

Impact of a motion correction algorithm on quality and diagnostic utility in unselected patients undergoing coronary CT angiography

AIMS

The aims of the study were to investigate the diagnostic utility of motion correction reconstruction algorithm Snapshot Freeze (SSF) compared to the standard reconstruction algorithm (STD) in coronary computed tomography angiography (CCTA) images where a prescan heart-rate-lowering protocol is fully integrated.

METHODS

CCTA was performed in 140 patients. Two independent blinded readers made image evaluation of the SSF and STD images.

RESULTS

SSF reduced the motion artifacts (30% vs. 41%; P<.05) and improved the image quality ("excellent" images: 52% vs. 42%; P=.022), but did not influence diagnostic utility ("nondiagnostic" images: 10% vs. 14%; P=.104).

CONCLUSION

The use of the SSF algorithm reduced the presence of motion artifacts and improved image quality, but did not influence the diagnostic utility.

Improved image quality at 256-slice coronary CT angiography in patients with a high heart rate and coronary artery disease: comparison with 64-slice CT imaging

BACKGROUND

The 256-slice computed tomography (CT) scanners with wider detector coverage and faster gantry rotation speed are now available. The performance of scanners that feature a rotation speed of 270 ms at coronary CT angiography (CCTA) has not been evaluated in patients with a higher heart rate.

PURPOSE

To evaluate the image quality of 256-slice CT with faster gantry rotation speed in patients undergoing CCTA.

MATERIAL AND METHODS

We enrolled 886 patients; 357(40.3%) underwent study on a 64-slice CT at a rotation speed of 420 ms, the other 529 (59.7%) were examined using a 256-slice CT scanner at 270 ms. Two observers judged the image quality of 2658 imaged coronary arteries on a 4-point scale.

RESULTS

The mean image quality score was significantly higher for the 256 - than the 64-slice CT scans (3.94 ± 0.28 vs. 3.73 ± 0.61; P < 0.01). There was no significant difference in the image quality scores between 64 - and 256-slice scans in patients whose heart rate (HR) was <60 bpm. However, in patients whose HR exceeded 60 bpm these scores were significantly higher for 256-slice CT images (P < 0.01).

CONCLUSION

CCTA performed on the 256-slice CT scanner yielded significantly better image quality in patients with an HR exceeding 60 bpm.

Prospectively ECG-Triggered Sequential Dual-Source Coronary CT Angiography in Patients with Atrial Fibrillation: Influence of Heart Rate on Image Quality and Evaluation of Diagnostic Accuracy

Objectives

To evaluate the effects of mean heart rate (HR) and heart rate variation (HRV) on image quality and diagnostic accuracy of prospectively ECG-triggered sequential dual-source coronary CT angiography (CCTA) in patients with atrial fibrillation (AF).

Methods

Eighty-five patients (49 women, 36 men; mean age 62.1±9.5 years) with persistent AF underwent prospectively ECG-triggered sequential second-generation dual-source CCTA. Tube current and voltage were adjusted according to body mass index (BMI) and iterative reconstruction was used. Image quality of coronary segments (four-point scale) and presence of significant stenosis (>50%) were evaluated. Diagnostic accuracy was analyzed in 30 of the 85 patients who underwent additional invasive coronary angiography (ICA).

Results

Only 8 of 1102 (0.7%) segments demonstrated poor image quality. No significant impact on image quality was found for mean HR (94.9±21.8 bpm; r=0.034, p=0.758; F=0.413, p=0.663) or HRV (67.5±22.8 bpm; r=0.097, p=0.377; F=0.111, p=0.895). On per-segment analysis, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 89.7% (26/29), 99.4% (355/357), 92.9% (26/28), and 99.2% (355/358), respectively, with excellent correlation (kappa=0.91) with ICA. Mean effective dose was 3.3±1.0 mSv.

Conclusions

Prospectively ECG-triggered sequential dual-source CCTA provides diagnostic image quality and good diagnostic accuracy for detection of coronary stenosis in AF patients without significant influence by HR or HRV.

Clinical significance of serum bilirubin and gamma-glutamyltransferase levels on coronary atherosclerosis assessed by multidetector computed tomography

BACKGROUND AND AIMS

Low bilirubin and high gamma-glutamyltransferase (GGT), which are endogenous markers of oxidative stress, confer a higher risk of cardiovascular disease (CVD). We investigated associations between serum concentrations of bilirubin, GGT and coronary atherosclerosis.

METHODS AND RESULTS

A cross-sectional analysis was performed on 1520 subjects who underwent multidetector computed tomography scans. Coronary atherosclerosis was assessed by coronary artery calcium score (CACS) and obstructive coronary artery disease (OCAD), was defined as the presence of coronary artery stenosis of ≥50%. Total bilirubin (TB) level was negatively correlated with CACS and coronary stenosis whereas GGT level was positively correlated with CACS in men. However, there was no correlation between TB, GGT levels and either CACS or coronary artery stenosis in women. In a multivariate-adjusted model, TB level was inversely associated with a CACS > 100 [odds ratio (OR) per log standard deviation (SD), 0.67; 95% confidence interval (CI), 0.52-0.87], and OCAD (OR per log SD, 0.77; 95% CI, 0.62-0.95) in men. By contrast, GGT level was positively associated with a CACS > 100 (OR per log SD, 1.35; 95% CI, 1.05-1.73) but not with OCAD. Adding TB and GGT to the conventional risk factors increased predictive accuracy for CACS > 100 (net reclassification improvement index [NRI] = 13.1%, P = 0.026; integrated discrimination index [IDI] = 0.024, P = 0.001) and for OCAD (NRI = 12.6%, P = 0.026; IDI = 0.010, P = 0.013).

CONCLUSIONS

Low TB and high GGT levels were concomitantly associated with coronary atherosclerosis in Korean men. Future studies are needed to elucidate the causal associations of TB and GGT with CVD.

Impact of an intra-cycle motion correction algorithm on overall evaluability and diagnostic accuracy of computed tomography coronary angiography

OBJECTIVES

The aim of this study was to evaluate the impact of a novel intra-cycle motion correction algorithm (MCA) on overall evaluability and diagnostic accuracy of cardiac computed tomography coronary angiography (CCT).

METHODS

From a cohort of 900 consecutive patients referred for CCT for suspected coronary artery disease (CAD), we enrolled 160 (18 %) patients (mean age 65.3 ± 11.7 years, 101 male) with at least one coronary segment classified as non-evaluable for motion artefacts. The CCT data sets were evaluated using a standard reconstruction algorithm (SRA) and MCA and compared in terms of subjective image quality, evaluability and diagnostic accuracy.

RESULTS

The mean heart rate during the examination was 68.3 ± 9.4 bpm. The MCA showed a higher Likert score (3.1 ± 0.9 vs. 2.5 ± 1.1, p < 0.001) and evaluability (94%vs.79 %, p < 0.001) than the SRA. In a 45-patient subgroup studied by clinically indicated invasive coronary angiography, specificity, positive predictive value and accuracy were higher in MCA vs. SRA in segment-based and vessel-based models, respectively (87%vs.73 %, 50%vs.34 %, 85%vs.73 %, p < 0.001 and 62%vs.28 %, 66%vs.51 % and 75%vs.57 %, p < 0.001). In a patient-based model, MCA showed higher accuracy vs. SCA (93%vs.76 %, p < 0.05).

CONCLUSIONS

MCA can significantly improve subjective image quality, overall evaluability and diagnostic accuracy of CCT.

KEY POINTS

Cardiac computed tomographic coronary angiography (CCT) allows non-invasive evaluation of coronary arteries. Intra-cycle motion correction algorithm (MCA) allows for compensation of coronary motion. An MCA improves image quality, CCT evaluability and diagnostic accuracy.

Low-dose CT coronary angiography with a novel IntraCycle motion-correction algorithm in patients with high heart rate or heart rate variability

AIMS

Motion artefacts due to high or irregular heart rate (HR) are common limitations of coronary computed tomography (CT) angiography (CCTA). The aim of the study was to evaluate the impact of a new motion-correction (MC) algorithm used in conjunction with low-dose prospective ECG-triggering CCTA on motion artefacts, image quality, and coronary assessability.

METHODS AND RESULTS

Among 380 patients undergoing CCTA for suspected CAD, we selected 120 patients with pre-scanning HR >70 bpm or HR variability (HRv) >10 bpm during scanning irrespective of pre-scanning HR or both conditions. In patients with pre-scanning HR <65 or ≥65 bpm, prospective ECG triggering with padding of 80 ms (58 cases) or padding of 200 ms (62 cases) was used, respectively. Mean pre-scanning HR and HRv were 70 ± 7 and 10.9 ± 4 bpm, respectively. Overall, the mean effective dose was 3.4 ± 1.3 mSv, while a lower dose (2.4 ± 0.9 mSv) was measured for padding of 80 ms. In a segment-based analysis, coronary assessability was significantly higher (P < 0.0001) with MC (97%) when compared with standard (STD) reconstruction (81%) due to a significant reduction (P < 0.0001) in severe artefacts (54 vs. 356 cases, respectively). An artefact sub-analysis showed significantly lower number of motion artefacts and artefacts related to chest movement with MC (16 and 4 cases) than with STD reconstruction (286 and 24 cases, P < 0.0001 and P < 0.05, respectively). The number of coronary segments ranked among those of excellent image quality was significantly higher with MC (P < 0.001).

CONCLUSIONS

The MC algorithm improves CCTA image quality and coronary assessability in patients with high HR and HRv, despite low radiation dose.

Cardiac radiology: centenary review

During the past century, cardiac imaging technologies have revolutionized the diagnosis and treatment of acquired and congenital heart disease. Many important contributions to the field of cardiac imaging were initially reported in Radiology. The field developed from the early stages of cardiac imaging, including the use of coronary x-ray angiography and roentgen kymography, to nowadays the widely used echocardiographic, nuclear medicine, cardiac computed tomographic (CT), and magnetic resonance (MR) applications. It is surprising how many of these techniques were not recognized for their potential during their early inception. Some techniques were described in the literature but required many years to enter the clinical arena and presently continue to expand in terms of clinical application. The application of various CT and MR contrast agents for the diagnosis of myocardial ischemia is a case in point, as the utility of contrast agents continues to expand the noninvasive characterization of myocardium. The history of cardiac imaging has included a continuous process of advances in our understanding of the anatomy and physiology of the cardiovascular system, along with advances in imaging technology that continue to the present day.

Multidetector-row computed tomography for noninvasive coronary imaging

Computed tomography (CT) permits cross-sectional imaging of the heart. Temporal and spatial resolutions of the technique have been insufficient to cover the heart without motion artefacts until the recent advent of multidetector systems with more than 16 detector rows. The modality is now suited for noninvasive imaging of the coronary arteries, producing detailed morphologic images of the entire coronary tree with upto 0.4 mm of spatial resolution, within a single short breath-hold duration. CT imaging goes beyond the delineation of the coronary lumen as provided by selective invasive angiography; the plaque burden of the coronary artery wall can be visualized directly, utilizing soft-tissue contrast and a high sensitivity even for the small calcifications that are present in hard plaque formations. Therefore, CT combines elements of catheterization angiography for lumen imaging and of intravascular ultrasound imaging for coronary wall imaging. However current CT technology is not yet able to compete with the temporal or spatial resolution of catheterization angiography nor does it provide the detailed spatial or contrast resolution of intravascular ultrasound imaging. At present, its use is therefore restricted to complementing the invasive modalities in appropriate indications. Although CT entails significantly less risk than the invasive procedures, the risks of radiation dose exposure and contrast agent application are not negligible. In the foreseeable future, if the current rate of technological advancement continues, CT may replace the invasive modalities in routine care for diagnostic purposes.

Quantitative analysis of motion artifacts in high-pitch dual-source computed tomography of the thorax

PURPOSE

The purpose of this study was to objectively analyze motion artifacts on thoracic computed tomography (CT) with dual-source high-pitch and single-source techniques when using a no-breath-hold technique to examine patients who have difficulty complying with breath-holding instructions.

MATERIALS AND METHODS

A total of 120 patients who received CT of the thorax with a free-breathing technique in single-source (16 slices and 128 slices; pitch = 1.2) and dual-source (pitch = 3.0) manners were evaluated retrospectively. In each of the 3 study groups, movements of the diaphragm and pulsations of the aortic root and main pulmonary artery were analyzed for their number and severity (blurred distance).

RESULTS

No motion artifacts of the diaphragm were identified using a pitch of 3.0 (compared with n = 14 for single-source CT using 128 slices and n = 24 using 16-slice CT). In single-source examinations, the severity of artifacts was similar between 128-slice CT and 16-slice CT: blurring distance of the lung parenchyma due to diaphragm movements was 14 versus 16 mm, and double contours of the aorta were measured as 8 and 9 mm, respectively.

CONCLUSIONS

A high-pitch, dual-source mode is potentially advantageous for evaluating the lung parenchyma and vascular structures in patients who have difficulty complying with breath-holding instructions. Increasing from 16 to 128 slices can significantly reduce the number and severity of motion artifacts.

Dual-source CT coronary angiography involving injection protocol with iodine load tailored to patient body weight and body mass index: estimation of optimal contrast material dose

BACKGROUND

Body mass index (BMI) has a positive linear influence on arterial attenuation at coronary CT angiography involving injection protocol with dose linearly tailored to body weight (BW). Excessive contrast material may inadvertently be given in heavier patients when the dose is determined by BW only.

PURPOSE

To investigate the effect of injection protocol with dose of contrast material (CM) tailored to BW and BMI on coronary arterial attenuation, contrast-to-noise ratio, and image noise at dual-source CT coronary angiography (DSCT-CA).

MATERIAL AND METHODS

A total of 233 consecutive patients (mean age, 60.2 years) undergoing DSCT-CA were included. Image acquisition protocol was standardized (120 kV, 380 mAs, and retrospective electrocardiograph-triggered DSCT-CA). CM dosage calculation was randomly categorized into groups: a BW group and a BW-BMI group. CM flow rate in both groups was calculated as dosage divided by scan time plus 8 s. Correlations between BW, BMI, and attenuations of ascending aorta (AA) above coronary ostia, left main coronary artery (LM), proximal right coronary artery (RCA), left anterior descending (LAD), and left circumflex artery (LCX), contrast to noise ratio of LM (LMCNR) and RCA (RCACNR), and image noise were evaluated with simple linear regression for two groups individually.

RESULTS

In BW group, attenuations of AA and coronary arteries showed positive linear correlations to BW and BMI. In contrast, no relationships were found in BW-BMI group. LMCNR and RCACNR were inversely determined by BW and BMI in both groups. Image noise increased with BW and BMI increasing in two groups.

CONCLUSION

BMI has a positive linear influence on arterial attenuation with fixed iodine per BW. The injection protocol with CM dose tailored to BW and BMI is reasonable during DSCT-CA.

Prospectively versus retrospectively ECG-gated 256-slice CT angiography to assess coronary artery bypass grafts--comparison of image quality and radiation dose

Objective

In this retrospective non-randomized cohort study, the image quality and radiation dose were compared between prospectively electrocardiogram (ECG)-gated axial (PGA) and retrospectively ECG-gated helical (RGH) techniques for the assessment of coronary artery bypass grafts using 256-slice CT.

Methods

We studied 124 grafts with 577 segments in 64 patients with a heart rate (HR) <85 bpm who underwent CT coronary angiography (CTCA); 34 patients with RGH-CTCA and 30 patients with PGA-CTCA. The image quality of the bypass grafts was assessed by a 5-point scale (1 = excellent to 5 = non-diagnostic) for each segment (proximal anastomosis, proximal, middle, distal course of graft body, and distal anastomosis). Other objective image quality indices such as noise, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) were assessed. Radiation doses were also compared.

Results

Patient characteristics of the two groups were well matched except HR. The HR of the PGA group was lower than that of the RGH group (62.0±5.0 vs. 65.7±7.4). For both groups, over 90% of segments received excellent or good image quality scores and none was non-evaluative. The image quality generally degraded as graft segment approached to distal anastomosis regardless of techniques and graft types. Image quality scores of the PGA group were better than those of the RGH group (1.51±0.53 vs. 1.73±0.62; p<0.001). There was no significantly difference of objective image quality between two techniques, and the effective radiation dose was significantly lower in the PGA group (7.0±1.2 mSv) than that of the RGH group (20.0±4.6 mSv) (p<0.001), with a 65.0% dose reduction.

Conclusions

Following bypass surgery, 256-slice PGA-CTCA is superior to RGH-CTCA in limiting the radiation dose and obtaining better image quality for bypass grafts.

A fully four-dimensional, iterative motion estimation and compensation method for cardiac CT

PURPOSE

To develop a new fully four-dimensional (4D), iterative image reconstruction algorithm for cardiac CT that alternates the following two methods: estimation of a time-dependent motion vector field (MVF) of the heart from image data and reconstruction of images using the estimated MVF and projection data.

METHODS

Volumetric image data at different cardiac phase points were obtained using electrocardiogram-gated CT. Motion estimation (ME) and motion-compensated image reconstruction (MCR) were performed alternately until convergence was achieved. The ME method estimated the cardiac MVF using 4D nonrigid image registration between a cardiac reference phase and all the other phases. The nonrigid deformation of the heart was modeled using cubic B-splines. The cost function consisted of a sum of squared weighted differences and spatial and temporal regularization terms. A nested conjugate gradient optimization algorithm was applied to minimize the cost function and estimate the MVFs. Cardiac images were reconstructed using a motion-tracking algorithm that utilized the MVFs estimated by the ME method. The reconstructed images supplied the input to the ME of the next iteration. The performance of the proposed method was evaluated using four patient data sets acquired with a 64-slice CT scanner. The heart rates of the patients ranged from 52 to 71 beats/min.

RESULTS

Motion artifacts were significantly reduced, and the image quality increased with the number of iterations. Without MCR, the right coronary artery (RCA) was deformed into an arc in axial images of rapid phases. With the proposed method the RCA appeared sharper and was reconstructed similar in shape to the reconstruction at the quiescent phase at mid-diastole. The boundary between the interventricular septum and the right ventricle was also clearer and sharper using the proposed algorithm. The steepness of the transition range at a rapid phase (35% R-R) was increased from 6.8 HU∕pixel to 11.5 HU∕pixel. The ME-MCR algorithm converged in just four iterations.

CONCLUSION

We developed a fully 4D image reconstruction method that alternates ME and MCR algorithms in an iterative fashion. Performance tests using clinical patient data resulted in reduced motion artifacts.

The influence of body mass index and gender on coronary arterial attenuation with fixed iodine load per body weight at dual-source CT coronary angiography

BACKGROUND

Most of current coronary CT angiography protocols are not adapted to body weight (BW) or cardiac output and no literature about influence of gender on coronary attenuation are reported with administration of a fixed iodine load per BW.

PURPOSE

To determine the influence of body mass index (BMI) and gender on coronary arterial attenuation if contrast material dose is linearly adjusted to a patient's BW at dual-source CT coronary angiography (DSCT-CA).

MATERIAL AND METHODS

A total of 207 consecutive patients (mean age 60.6 years) undergoing DSCT-CA were included. Contrast material (370 mg I/mL) dose calculation was randomly categorized into two groups (Group 1: 1.10 mL/kg for men and women; Group 2: men 1.10 mL/kg, women 0.99 mL/kg) and flow rate was calculated as dose was divided by scan time plus 8 s. Mean arterial attenuations between men and women were compared with respect to attenuations of ascending aorta (AA) above coronary ostia, left main coronary artery (LM), proximal segments of right coronary artery (RCA), left anterior descending (LAD), and left circumflex artery (LCX) in two groups, respectively. Attenuations of coronary arteries were correlated with BW and BMI with simple linear regression.

RESULTS

The mean attenuations of AA, LM, RCA, LAD, and LCX were 407.8 ± 53.6 HU, 412.6 ± 55.4 HU, 411.4 ± 64.3 HU, 399.1 ± 56.7 HU, and 399.1 ± 60.2 HU, respectively, and there were no significant differences between men and women in group 1 (AA, P = 0.571; LM, P = 0.670; RCA, P = 0.737; LAD, P = 0.439, and LCX, P = 0.888). In group 2, the mean attenuations of AA, LM, RCA, LAD, and LCX in men were significantly higher than those in women (AA, P = 0.008; LM, P = 0.025; RCA, P = 0.017; LAD, P = 0.015, and LCX, P = 0.002). Positive linear regression between BW and attenuations of AA (R(2) = 0.047, P = 0.02), LM (R(2) = 0.036, P = 0.04), RCA (R(2) = 0.080, P < 0.01), LAD (R(2) = 0.078, P < 0.01), and LCX (R(2) = 0.033, P = 0.05) was found in group 1, suggesting that attenuations of coronary arteries increased in heavier patients. Similarly, there was positive linear regression between BMI and attenuations of AA (R(2) = 0.117, P < 0.01), LM (R(2) = 0.090, P < 0.01), RCA (R(2) = 0.138, P < 0.01), LAD (R(2) = 0.111, P < 0.01), and LCX (R(2) = 0.078, P < 0.01).

CONCLUSION

Men and women have similar coronary attenuations with a fixed iodine load per BW. BMI has a positive linear influence on arterial attenuation at DSCT-CA involving injection protocol with dose linearly tailored to BW. Excessive contrast material may inadvertently be given in heavier patients when the dose is determined by BW only. Contrast material dose may need to be tailored individually by BW and BMI.

Diagnostic accuracy of 320-slice computed-tomography for detection of significant coronary artery stenosis in patients with various heart rates and heart rhythms compared with conventional coronary-angiography

PURPOSE

To evaluate the diagnostic accuracy of 320-slice CT for detection of significant coronary artery stenosis in patients with various heart rates (HR) and heart rhythms, including tachycardia and chronic atrial-fibrillation (CAF) compared with conventional-coronary-angiography (CAG).

MATERIALS AND METHODS

One-hundred-six consecutive patients underwent both 320-slice CT and CAG within 3 months (normal-sinus-rhythm [NSR] 91.5%, CAF 8.5%, mean HR 65 ± 15 beats/min). There were no cardiac events between the 2 procedures. Patients were divided in 2 groups: Group 1 (HR <65 with NSR at CT scan, n=62), and Group 2 (HR >64 with NSR or heart rhythm irregularities at CT scan, n=44). Patients with >50% or >75% luminal stenosis on CT were compared with those with >50% or >75% stenosis on CAG, respectively.

RESULTS

In a segment-by-segment analysis, in all patients, sensitivity, specificity, positive (PPV) and negative predictive value (NPV) of >50% stenosis on CT for predicting >50% stenosis on CAG were 69, 98, 78, and 97%, respectively, and those of >75% stenosis on CT for predicting >75% stenosis on CAG were 78, 98, 64, and 99%, respectively. Sensitivity, specificity, PPV, and NPV of >50% and 75% stenosis on CT for predicting >50% and >75% stenosis, respectively, on CAG were comparable. Diagnostic accuracy was essentially the same in both groups.

CONCLUSION

320-slice CT had high diagnostic accuracy for the detection of significant coronary artery stenosis compared with CAG. Even though the numbers were small, patients with high HR or heart rhythm irregularities might have essentially equivalent results to those with low HR with NSR.

SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT

Over the last few years, computed tomography (CT) has developed into a standard clinical test for a variety of cardiovascular conditions. The emergence of cardiovascular CT during a period of dramatic increase in radiation exposure to the population from medical procedures and heightened concern about the subsequent potential cancer risk has led to intense scrutiny of the radiation burden of this new technique. This has hastened the development and implementation of dose reduction tools and prompted closer monitoring of patient dose. In an effort to aid the cardiovascular CT community in incorporating patient-centered radiation dose optimization and monitoring strategies into standard practice, the Society of Cardiovascular Computed Tomography has produced a guideline document to review available data and provide recommendations regarding interpretation of radiation dose indices and predictors of risk, appropriate use of scanner acquisition modes and settings, development of algorithms for dose optimization, and establishment of procedures for dose monitoring.

Radiation dose and diagnostic accuracy of multidetector computed tomography for the detection of significant coronary artery stenoses: a meta-analysis

We conducted a meta-analysis evaluating the critical ratio between effective radiation dose (ED), feasibility (Fe) and diagnostic accuracy (Ac) of multidetector computed tomography (MDCT) for the detection of significant coronary artery disease. By using our predetermined criteria, we selected human studies published in English in which the ED and raw data of Ac vs. invasive coronary angiography in a segment based model were specified. Data from 31 studies including 3661 patients (mean age 61.9 ± 4.5 years, heart rate 62.5 ± 6.7 bpm) and 50,236 coronary artery segments were analysed and are reported. Overall, Fe, sensitivity, specificity, negative predictive value, positive predictive value, Ac and ED were 95%, 90%, 96%, 99%, 69%, 95% and 10.4 ± 5.4 mSv, respectively. Multivariate analysis showed that prospective ECG-gating (-8.8 mSv CI95% -13.4 to -4.3 mSv, p=0.001), dual-source (-3.7 mSv CI95% -7.9 to 0 mSv, p=0.05) and BMI-adapted scanning protocols (-4.5 mSv CI95% -8.7 to -2.7 mSv, p=0.03) were independent predictors of ED reduction. In patients with low heart rate, the best compromise between ED, Fe and Ac (2.5 mSv, 97% and 98%, respectively) was obtained combining prospective ECG-gating and BMI-adapted scanning protocols, while in patients with high heart rate the strategy associated with the best results (10 mSv, 98% and 97%, respectively) was the use of dual-source MDCT with retrospective ECG gating and modulation dose. In conclusion, careful selection of CT scanning protocols according to the patient's characteristics is critical for keeping the radiation exposure "as low as reasonably achievable" (ALARA) without impairing Fe and Ac.