Long-term prognostic value of whole-heart coronary magnetic resonance angiography.

BACKGROUND: Coronary magnetic resonance angiography (CMRA) allows non-ionizing visualization of luminal narrowing in coronary artery disease (CAD). Although a prior study showed the usefulness of CMRA for risk stratification in short-term follow-up, the long-term prognostic value of CMRA remains unclear. The purpose of this study was to evaluate the long-term prognostic value of CMRA. METHODS: A total of 506 patients without history of myocardial infarction or prior coronary artery revascularization underwent free-breathing whole-heart CMRA between 2009 and 2015. Images were acquired using a 1.5 T or 3 T scanner and visually evaluated as the consensus decisions of two observers. Obstructive CAD on CMRA was defined as luminal narrowing of ≥ 50% in at least one coronary artery. Major adverse cardiac events (MACE) comprised cardiac death, nonfatal myocardial infarction, and unstable angina. RESULTS: Obstructive CAD on CMRA was observed in 214 patients (42%). During follow-up (median, 5.6 years), 31 MACE occurred. Kaplan-Meier curve analysis revealed a significant difference in event-free survival between patients with and without obstructive CAD for MACE (log-rank, p = 0.003) and cardiac death (p = 0.012). Annualized event rates for MACE in patients with no obstructive CAD, 1-vessel disease, 2-vessel disease, and left-main or 3-vessel disease were 0.6%, 1.5%, 2.3%, and 3.6%, respectively (log-rank, p = 0.003). Cox proportional hazard regression analysis showed that, among obstructive CAD on CMRA and clinical risk factors (age, sex, hypertension, diabetes, dyslipidemia, smoking, and family history of CAD), obstructive CAD and diabetes were significant predictors of MACE (hazard ratios, 2.9 [p = 0.005] and 2.2 [p = 0.034], respectively). In multivariate analysis, obstructive CAD remained an independent predictor (adjusted hazard ratio, 2.6 [p = 0.010]) after adjusting for diabetes. Addition of obstructive CAD to clinical risk factors significantly increased the global chi-square result from 8.3 to 13.8 (p = 0.022). CONCLUSIONS: In long-term follow-up, free breathing whole heart CMRA allows non-invasive risk stratification for MACE and cardiac death and provides incremental prognostic value over conventional risk factors in patients without a history of myocardial infarction or prior coronary artery revascularization. The presence and severity of obstructive CAD detected by CMRA were associated with worse prognosis. Importantly, patients without obstructive CAD on CMRA displayed favorable prognosis.

Pacemaker-induced Metallic Artifacts in Coronary Computed Tomography Angiography: Clinical Feasibility of Single Energy Metal Artifact Reduction Technique.

BACKGROUND: Coronary computed tomography angiography (CCTA) in patients with pacemaker suffers from metallic lead-induced artifacts, which often interfere with accurate assessment of coronary luminal stenosis. The purpose of this study was to assess a frequency of the lead-induced artifacts and artifact-suppression effect by the single energy metal artifact reduction (SEMAR) technique. METHODS: Forty-one patients with a dual-chamber pacemaker were evaluated using a 320 multi-detector row CT (MDCT). Among them, 22 patients with motion-free full data reconstruction images were the final candidates. Images with and without the SMEAR technique were subjectively compared, and the degree of metallic artifacts was compared. RESULTS: On images without SEMAR, severe metallic artifacts were often observed in the right coronary artery (#1, #2, #3) and distal anterior descending branch (#8). These artifacts were effectively suppressed by SEMAR, and the luminal accessibility was significantly improved in #3 and #8. CONCLUSION: While pacemaker leads often cause metallic-induced artifacts, SEMAR technique reduced the artifacts and significantly improved the accessibility of coronary lumen in #3 and #8.

[The Minimum Values of (RR-PQ) for High Quality Coronary CT Angiogram in Half, Automatic Patient's Motion Correction (APMC) and Full Reconstruction Using 320-ADCT (0.275 s/r)].

BACKGROUND: A clear coronary CT angiography (CCTA) can be obtained when temporal resolution (TR) is shorter than slow filling (SF) duration. The SF duration was calculated by the following equation: SF=-443+0.742 (RR-PQ). Although, the TR of half and full reconstruction using 320-ADCT (0.275 s/r) are known, the TR of automatic patient motion correction (APMC) reconstruction is not clear. The purpose of this study is to clarify the each minimum value of (RR-PQ) for acquiring a clear CCTA that was made by half, full or APMC reconstruction. METHOD: CCTA was performed in consecutive 345 (M/F=195/150, Age: 69±10 years) patients except for arrhythmia and the final heart rate (controlled by ß-blocker) ≥80 bpm using 320-ADCT (Aquilion ONE, 0.275 s/r). In all subjects, 3 CCTAs were generated by half, full, or APMC reconstruction at the same optimal phase. Image quality (A: excellent, B: acceptable, C: poor) was estimated by the consensus of three trained researchers. We classified (RR-PQ) into 15 groups by each 50 ms interval. RESULTS: The A or B % prediction (y) significantly correlated (y=-240.08+0.401x, r=0.98, p=0.0006 in half, y=-238.26+0.378x, r=0.98, p=0.0001 in APMC, and y=-236.84+0.332x, r=0.97, p<0.0001 in full reconstruction) with (RR-PQ) (x), respectively. CONCLUSION: The minimum values of (RR-PQ) for 95% prediction of A or B image quality were ≥836 ms in half, ≥881 ms in APMC, and ≥998 ms in full reconstruction.

Development of new risk score for pre-test probability of obstructive coronary artery disease based on coronary CT angiography.

Existing methods to calculate pre-test probability of obstructive coronary artery disease (CAD) have been established using selected high-risk patients who were referred to conventional coronary angiography. The purpose of this study is to develop and validate our new method for pre-test probability of obstructive CAD using patients who underwent coronary CT angiography (CTA), which could be applicable to a wider range of patient population. Using consecutive 4137 patients with suspected CAD who underwent coronary CTA at our institution, a multivariate logistic regression model including clinical factors as covariates calculated the pre-test probability (K-score) of obstructive CAD determined by coronary CTA. The K-score was compared with the Duke clinical score using the area under the curve (AUC) for the receiver-operating characteristic curve. External validation was performed by an independent sample of 319 patients. The final model included eight significant predictors: age, gender, coronary risk factor (hypertension, diabetes mellitus, dyslipidemia, smoking), history of cerebral infarction, and chest symptom. The AUC of the K-score was significantly greater than that of the Duke clinical score for both derivation (0.736 vs. 0.699) and validation (0.714 vs. 0.688) data sets. Among patients who underwent coronary CTA, newly developed K-score had better pre-test prediction ability of obstructive CAD compared to Duke clinical score in Japanese population.

[Clinical usefulness of low tube current scanning with full reconstruction and automatic patient motion correction (APMC) reconstruction in a prospective ECG-gated coronary CT angiography using 320-row area detector CT].

PURPOSE: The purpose of this study is to validate the clinical usefulness of Advanced Patient Motion Correction (APMC) reconstruction when motion artifacts were observed in a prospective ECG-gated coronary CT angiography (CCTA), which was acquired by low tube current scanning with full reconstruction using 320-row area detector CT (0.275 s/rot.). METHODS: Of 530 consecutive CCTA, we selected 119 patients (M/F: 71/48, Age: 69 ± 11 y, BMI: 23.5 ± 2.5) with (RR-PQ) ≥ 968 ms before scanning, and performed a CCTA with low tube current scanning [30% of usual tube current (30%mA)], adaptive iterative dose reduction 3D, and full reconstruction. Image quality for motion artifacts was subjectively evaluated using a 3-point scale (excellent, acceptable, and unacceptable). RESULTS: Of 119, 102 CCTA had "excellent" images (group A) and 17 had "acceptable" images (group B). The APMC and half reconstruction were retried in the 17 CCTA with "acceptable" images. Finally, all CCTA became "excellent" images. The RR-PQ of group B during scanning (966 ± 80 ms) was significantly (P = 0.0001) shorter than group A (1,088 ± 123 ms). Each image noise (standard deviation of CT value) of aorta, left atrium, and left ventricle was 21.7 ± 2.3, 24.7 ± 2.3, 24.5 ± 2.4 in full, 25.7 ± 2.2, 29.0 ± 3.4, 28.2 ± 2.7 in APMC, and 30.4 ± 2.8, 34.3 ± 4.2, 33.3 ± 2.9 HU in half reconstruction. Mean dose-length product of all patients was 66.2 ± 34.4 mGy · cm. CONCLUSION: "Excellent" CCTA images can be obtained in 85.7% of patients with (RR-PQ)≥ 968 ms by full reconstruction. APMC is useful for motion artifacts and image noise reduction when patient' s HR increases during scanning rather than half reconstruction.

Optimal Protocol for Contrast-enhanced Free-running 5D Whole-heart Coronary MR Angiography at 3T.

Free-running 5D whole-heart coronary MR angiography (MRA) is gaining in popularity because it reduces scanning complexity by removing the need for specific slice orientations, respiratory gating, or cardiac triggering. At 3T, a gradient echo (GRE) sequence is preferred in combination with contrast injection. However, neither the injection scheme of the gadolinium (Gd) contrast medium, the choice of the RF excitation angle, nor the dedicated image reconstruction parameters have been established for 3T GRE free-running 5D whole-heart coronary MRA. In this study, a Gd injection scheme, RF excitation angles of lipid-insensitive binominal off-resonance RF excitation (LIBRE) pulse for valid fat suppression and continuous data acquisition, and compressed-sensing reconstruction regularization parameters were optimized for contrast-enhanced free-running 5D whole-heart coronary MRA using a GRE sequence at 3T. Using this optimized protocol, contrast-enhanced free-running 5D whole-heart coronary MRA using a GRE sequence is feasible with good image quality at 3T.

Image quality and radiation dose stratified by patient heart rate for coronary 64- and 320-MDCT angiography.

OBJECTIVE. The purpose of this study is to retrospectively measure and compare estimated radiation doses between consecutive patient cohorts who underwent coronary imaging CT with 64- and 320-MDCT scanners. MATERIALS AND METHODS. Subjects without arrhythmia (n = 4475) underwent imaging with 64-MDCT (n = 770) and 320-MDCT (n = 3705) scanners and were classified into one of five subgroups according to the patient heart rate and the image acquisition strategy. For all patients, image quality was subjectively evaluated using a 3-point scale. Estimated radiation dose and image quality were compared between subjects stratified by CT scanner and by subgroups imaged with each technology. RESULTS. For patients with a heart rate of 60 beats/min or less, the estimated radiation dose was halved (3.8 ± 2.0 vs 7.6 ± 2.6 mSv) when the 320-MDCT scanner (n = 2787) replaced the 64-MDCT scanner (n = 511). For the entire cohort, image quality score was significantly better (2.9 ± 0.4 vs 2.8 ± 0.5; p < 0.0001) and the effective dose was significantly lower (4.9 ± 3.3 vs 9.9 ± 5.4 mSv; p < 0.0001) for 320-MDCT scanners, compared with 64-MDCT scanners. CONCLUSION. Wide area-detector coronary CT angiography protocols have reduced radiation dose, with image quality maintained at the same level, compared with 64-MDCT technologies.

Prospective ECG-gated coronary 320-MDCT angiography with absolute acquisition delay strategy for patients with persistent atrial fibrillation.

OBJECTIVE: The purpose of this study was to evaluate image quality and radiation dose when patients with atrial fibrillation undergo coronary CT angiography (CTA) using prospectively ECG-gated 320-MDCT technology with an absolute-delay strategy. MATERIALS AND METHODS: A cohort of 75 consecutive patients (60 men and 15 women; age (± SD), 71 ± 10 years) who underwent prospectively ECG-gated coronary CTA using a 320-MDCT scanner during atrial fibrillation was matched with 75 control patients imaged in sinus rhythm. All coronary CTA for the atrial fibrillation cohort used absolute-delay strategy. Subjective image quality score and the dose-length product (DLP) were compared between the two cohorts and, for the atrial fibrillation cohort, among those patients imaged over a different number of heartbeats. The accuracy of stenosis detection was evaluated in 17 studies of the atrial fibrillation cohort using catheter angiography as a reference standard. RESULTS: For those patients imaged in atrial fibrillation, one- and two-beat acquisitions were performed in 26.7% (n = 20) and 40% (n = 30) of patients, respectively. There was no significant difference in image quality between the atrial fibrillation (2.9 ± 0.4) and sinus rhythm (2.9 ± 0.3) cohorts, nor was there a difference in image quality with respect to the number of heartbeats used in the acquisition. The atrial fibrillation cohort had an 80% higher DLP (680 ± 470 vs 372 ± 236 mGy × cm, p < 0.0001). The patient-based sensitivity and negative predictive value for stenosis detection were both 100%. CONCLUSION: Using an absolute-delay strategy, two thirds of patients who underwent prospectively ECG-gated coronary CTA using a 320-MDCT scanner were imaged within two heartbeats or fewer. Compared with patients imaged in sinus rhythm, the image quality was comparative and the radiation dose was 1.8-fold higher.

[Prospective electrocardiogram gated coronary 320-row area detector computed tomography angiography using low tube current scanning with full reconstruction].

BACKGROUND: It is possible to obtain equivalent image quality and a lower radiation dose using low tube current scanning with full reconstruction as compared to usual tube current scanning with half reconstruction in a 320-row area detector computed tomography (ADCT) angiography. METHOD: Of 589 patient underwent coronary CT angiography (CCTA), 11 patients with (RR-PQ) ≥1069 ms were enrolled. In those patients, low tube current (50% mA) scanning with full or half reconstruction were performed. As a control, 11 patients with matched pairs of tube voltage, BMI and heart rate who underwent usual scanning with half reconstruction (100% mA with half reconstruction) were selected. Standard deviation of the CT value (SD) was measured in aorta (Ao), left atrium (LA) and left ventricle (LV), and extended dose-length products (DLP.e) were calculated. RESULT: Significant motion artifact was not observed in any patients. SD of 50% mA with half reconstruction, 50% mA with full reconstruction, and 100% mA with half reconstruction were 28.1±2.6, 20.3±1.9, 20.7±2.5 HU in Ao, 34.4±4.4, 24.9±2.8, 24.9±3.1 HU in LA, and 29.7±2.3, 21.7±1.9, 22.1±2.3 HU in LV, respectively. There were not significant differences between 50% mA with full reconstruction and 100% mA with half reconstruction, but there were significant differences between 50% mA with half reconstruction and 50% mA with full reconstruction in all sites. The DLP.e of 50% mA scanning (74.1±21.8 mGy·cm) was significantly lower than 100% mA scanning (161.9±28.9 mGy·cm). CONCLUSION: CCTA with lower radiation dose and equivalent image quality can be obtained by ADCT using 50% mA scanning with full reconstruction in patients with (RR-PQ) ≥1069 ms.

Coronary computed tomography angiography-based coronary risk stratification in subjects presenting with no or atypical symptoms.

BACKGROUND: Coronary computed tomography angiography (CTA) findings of positive vessel remodeling and low-attenuation plaque, referred to as computed tomography-verified high-risk plaque (CT-HRP), have been reported to be associated with the development of subsequent acute coronary syndromes. The aim of this study was to examine the usefulness of coronary CTA for coronary risk re-stratification of patients with asymptomatic and atypical chest symptoms. METHODS AND RESULTS: A total of 1,139 subjects (M/F 602/537; mean age, 61.5±9.3 years) who were either asymptomatic or presented with atypical chest symptoms underwent coronary 64- or 320-slice multidetector computed tomography angiography and Agatston score. Age, sex, coronary risk factors, including hypertension, diabetes mellitus (DM), dyslipidemia, and smoking were investigated as predictors for CT-HRP on multivariate analysis using logistic regression analysis. CT-HRP was observed in 72 patients (6.3%). Based on Framingham risk scores (FRS), CT-HRP was observed in 0/94 subjects (0.0%) in the low-risk group, 35/806 (4.3%) in the intermediate-risk group, and 37/239 (15.5%) in the high-risk group. On logistic regression analysis significant predictors for CT-HRP in intermediate- and high-risk subjects were male sex (odds ratio [OR] 2.829; 95% confidence interval [CI] 1.460-5.479, P=0.0021), DM (OR 2.418; 95% CI 1.420-4.116, P=0.0011), and current smoking (OR 1.922; 95% CI 1.096-3.371, P=0.0160). CT-HRP prevalence for Agatston scores >500 and >250 was lower in the intermediate- and high-risk groups, respectively. CONCLUSIONS: In asymptomatic subjects and those presenting with atypical chest pain who have a more than an intermediate risk, coronary CTA is contributory to FRS. Male sex, DM and smoking were independent predictors of vulnerable plaque in the more than intermediate-risk group.

[Comparison of the probability of meeting up with premature contraction during scanning in 320-area detector computed tomography with that in 64-multidetector CT coronary angiography].

BACKGROUND: Because coronary computed tomography angiography (CCTA) by 320-area detector CT (320-ADCT) can be obtained in a short time, the probability of meeting up with premature contraction (PC) during scanning may be lower in 320-ADCT compared to 64-MDCT. The purpose is to compare the probability of meeting up with PC, scanning time, and image quality in patients with PC between the 2 groups (320-ADCT vs 64-MDCT). METHODS: We have never rejected any CCTA examination due to arrhythmias. The 320-ADCT was performed in 2424 consecutive patients to include 70 atrial fibrillations (Afibs) and 64-MDCT in 1905 consecutive patients to include 51 Afibs. After exclusion of the patients with Afibs, we studied the probability of meeting up with PC during scanning and we compared the scanning time, image quality, and reconstruction phase for patients with PC between the 2 groups. RESULTS: The probability of meeting up with PC during scanning in 320-ADCT (2.0%) is significantly lower (P<0.0001) than 64-MDCT (5.6%). For patients with PC, scanning time in 320-ADCT (2.9±0.6 s) was significantly shorter (P<0.0001) than 64-MDCT (9.5±1.9 s) and image quality in 320-ADCT (2.9±0.3 points) was significantly higher (P<0.0001) than 64-MDCT (2.2±0.8 points). CCTA was reconstructed in mid-diastolic phase in 93% of patients with PC using the 320-ADCT with arrhythmia rejection system. CONCLUSION: The scanning time of 320-ADCT was 1/3 in comparison with that of 64-MDCT, and the probability of meeting up with PC during scanning in 320-ADCT was 1/3 in comparison with that in 64-MDCT.

Semiautomated Segmentation and Volume Measurements of Cervical Carotid High-Signal Plaques Using 3D Turbo Spin-Echo T1-Weighted Black-Blood Vessel Wall Imaging: A Preliminary Study.

Unstable carotid plaques are visualized as high-signal plaques (HSPs) on 3D turbo spin-echo T1-weighted black-blood vessel wall imaging (3D TSE T1-BB VWI). The purpose of this study was to compare manual segmentation and semiautomated segmentation for the quantification of carotid HSPs using 3D TSE T1-BB VWI. Twenty cervical carotid plaque lesions in 19 patients with a plaque contrast ratio of > 1.3 compared to adjacent muscle were studied. Using the mean voxel value for the adjacent muscle multiplied by 1.3 as a threshold value, the semiautomated software exclusively segmented and measured the HSP volume. Manual and semiautomated HSP volumes were well correlated (r = 0.965). Regarding reproducibility, the inter-rater ICC was 0.959 (bias: 24.63, 95% limit of agreement: −96.07, 146.35) for the manual method and 0.998 (bias: 15.2, 95% limit of agreement: −17.83, 48.23) for the semiautomated method, indicating improved reproducibility by the semiautomated method compared to the manual method. The time required for semiautomated segmentation was significantly shorter than that of manual segmentation times (81.7 ± 7.8 s versus 189.5 ± 49.6 s; p < 0.01). The results obtained in this study demonstrate that the semiautomated segmentation method allows for reliable assessment of the HSP volume in patients with carotid plaque lesions, with reduced time and effort for the analysis.

Evaluation of placental oxygenation index using blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) during normal late pregnancy.

AIM: Noninvasive blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) has recently been used to evaluate placental oxygenation. However, this method still has unresolved problems, such as long testing times and lack of normal values set. In the present study, we used a shorter protocol in BOLD-MRI and established normal values for placental oxygenation in late pregnancy. METHODS: We recruited 18 healthy singleton pregnant women (>32 weeks of gestation) who had a normal body size before pregnancy and a normal course of pregnancy. They underwent BOLD-MRI with three consecutive 4-min periods of different oxygenation: normoxia (21% O2), hyperoxia (10 L O2/min), and then normoxia. Placental time-activity curves were presented as signal intensity change relative to baseline (ΔR2*). The time from starting maternal oxygen administration to peak ΔR2*. To assess the relationship between peak ΔR2* values and placenta-related parameters and fetal development, the correlation between peak ΔR2*, placental weight, and neonatal birth weight was evaluated using Spearman's rank correlation test. RESULTS: In all cases, the BOLD signal was elevated by maternal oxygen administration, with the peak resolving within 4 min after the end of oxygen administration. Peak ΔR2* and time to peak ΔR2* during oxygenation were 7.99 ± 2.58, and 458.1 ± 73.9 s, respectively. There was a significant correlation between peak ΔR2* and neonatal birth weight (percentile) (r = 0.537, p = .022), and between placental weight and neonatal birth weight (r = 0.769, p < .01). CONCLUSIONS: In all cases, the BOLD signal increased with maternal hyperoxia using this protocol. So, 4 min observation following maternal oxygen administration is sufficient for peak ΔR2* evaluation. These reference values set in this study may be one of the indicators of BOLD signal changes in normal pregnancies after 32 weeks of gestation.

Quantification of myocardial blood flow using model based analysis of first-pass perfusion MRI: extraction fraction of Gd-DTPA varies with myocardial blood flow in human myocardium.

For the absolute quantification of myocardial blood flow (MBF), Patlak plot-derived K1 need to be converted to MBF by using the relation between the extraction fraction of gadolinium contrast agent and MBF. This study was conducted to determine the relation between extraction fraction of Gd-DTPA and MBF in human heart at rest and during stress. Thirty-four patients (19 men, mean age of 66.5 ± 11.0 years) with normal coronary arteries and no myocardial infarction were retrospectively evaluated. First-pass myocardial perfusion MRI during adenosine triphosphate stress and at rest was performed using a dual bolus approach to correct for saturation of the blood signal. Myocardial K1 was quantified by Patlak plot method. Mean MBF was determined from coronary sinus flow measured by phase contrast cine MRI and left ventricle mass measured by cine MRI. The extraction fraction of Gd-DTPA was calculated as the K1 divided by the mean MBF. The extraction fraction of Gd-DTPA was 0.46 ± 0.22 at rest and 0.32 ± 0.13 during stress (P < 0.001). The relationship between extraction fraction (E) and MBF in human myocardium can be approximated as E = 1 - exp(-(0.14 × MBF + 0.56)/MBF). The current results indicate that MBF can be accurately quantified by Patlak plot method of first-pass myocardial perfusion MRI by performing a correction of extraction fraction.

Impact of an abdominal belt on breathing patterns and scan efficiency in whole-heart coronary magnetic resonance angiography: comparison between the UK and Japan.

BACKGROUND: Long acquisition times and complex breathing motion patterns lead to suboptimal image quality in whole heart coronary magnetic resonance angiography (WHCMRA). To overcome this problem, an abdominal belt (BELT) has been suggested by a Japanese group. However, its applicability in a Western population has not been previously demonstrated. The purpose of this study was to investigate 1) how the application of a BELT alters breathing patterns during MR scanning and 2) whether the BELT has a similar impact on breathing patterns in UK and Japanese patient populations. METHODS: 30 patients (15 in the UK and 15 in Japan) were studied at 1.5 Tesla (Achieva, Philips Healthcare). Real time navigator positioned through the right diaphragm in cranio-caudal direction was evaluated. Measurements were performed in the supine position with free breathing for one minute before and after a tight-fitting BELT was positioned around the patient's abdomen. End expiratory position (EEP), end inspiratory position (EIP), end expiratory duration (EED) for the right diaphragm and respiratory rate (RR) were obtained. Scan efficiency (SE) was calculated as follows; SE = [the duration within 5 mm gating window per minutes]/[RR interval]/[heart rate]. RESULTS: Height and weight of UK patients were significantly larger than in the Japanese population (171.2 ± 10.8 cm vs 160.8 ± 8.5 cm, p = 0.007; 80.5 ± 22.5 kg vs 59.9 ± 7.7 kg, p = 0.004). After fitting the BELT, EEP-EIP decreased (all patients, 14.9 ± 6.2 mm to 9.4 ± 3.8 mm, p < 0.001; UK patients, 15.9 ± 6.0 mm to 9.7 ± 3.1 mm, p = 0.001; Japanese patients, 14.0 ± 6.4 mm to 9.1 ± 4.6 mm, p = 0.001), RR increased (all patients, 10.0 ± 3.1 min(-1) to 11.2 ± 3.0 min(-1), p = 0.003; UK patients, 9.5 ± 2.8 min(-1) to 10.7 ± 2.8 min(-1), p = 0.038; Japanese patients, 10.4 ± 3.5 min(-1) to 11.8 ± 3.1 min(-1), p = 0.036), and calculated scan efficiency increased (all patients, 45.3 ± 11.4% to 58.6 ± 17.0%, p < 0.001; UK patients, 44.2 ± 10.8% to 55.7 ± 16.7%, p = 0.004; Japanese patients, 46.3 ± 32.2% to 61.0 ± 17.6%, p = 0.001). No significant differences were found between UK and Japanese patients before and after administration of the BELT. CONCLUSION: Using a BELT significantly increases whole-heart coronary MR angiography scan efficiency in both UK and Japanese patients.

[Radiation dose reduction effects of prospective ECG-gated helical scan with high helical pitch in coronary multidetector computed tomography].

BACKGROUND: High radiation dose of conventional retrospective ECG-gated coronary MDCT (multidetector computed tomography) with regular helical pitch (HP) continuous scan has disturbed wide clinical use. The purpose was to estimate the radiation dose reduction effects of FlashScan, which was a prospective ECG-gated helical scan with high HP. METHOD: Coronary MDCT was performed by Aquilion 64 Super Heart (Toshiba) in 474 patients (M/F=280/194, mean age: 65+/-11 years old, mean height: 161+/-10 cm, body weight: 62+/-13 kg, BMI: 23.9+/-3.4) with HR

[Usefulness and safety of propranolol injection into vein for acquisition of coronary multidetector-row computed tomography].

BACKGROUND: A low heart rate (HR), associated with a prolonged slow filling phase (SF), is necessary to obtain a high quality coronary CT at a low radiation dose with conventional 64 multidetector-row computed tomography (MDCT). The purpose of our study was to confirm the safety of injecting propranolol (2-10 mg) into the vein for lowering heart rate in patients requiring MDCT and to document the effect of the drug on HR, PQ and SF. METHOD: Of 1290 consecutive patients who were initially considered for enrollment in the coronary MDCT study, 40 patients with atrial fibrillations, 3 with atrial flutters, and 13 with artificial pacemakers were excluded. Of the remaining 1234 patients (M/F=714/520), 331 had already taken an oral beta-blocker before the CT examination, and were included in the study. In patients with no contraindications, propranolol was aggressively injected (2-10 mg) into the vein to reduce the HR. RESULT: In patients not taking an oral beta blocker, 2 mg propranolol reduced the HR by -10±5 bpm and 10 mg, by -20±7 bpm. However, in patients taking an oral beta-blocker, the decrease in HR by propranolol was minimal (2 mg, -6±4 bpm; 10 mg, -10±6 bpm). Propranolol significantly prolonged the PQ interval (from 169±27 to 179±29 ms, P<0.0001), and SF (from 125±69 to 264±79 ms, P<0.0001). Adverse effects of propranolol injection were observed in only 3 [2 mild hypotension and 1 paroxysmal atrial fibrillation (recovered to sinus rhythm by DC counter shock)] of 3212 patients. All 3 patients became stable after 1 or 2 hours of rest and could return home. CONCLUSION: Propranolol injection was a relatively safe and useful method to reduce HR and prolong SF, necessary for obtaining high quality coronary MDCT with a low radiation dose.

[Comparison of radiation dose reduction of prospective ECG-gated one beat scan using 320 area detector CT coronary angiography and prospective ECG-gated helical scan with high helical pitch (FlashScan) using 64 multidetector-row CT coronary angiography].

BACKGROUND: A high radiation dose associated with 64 multidetector-row computed tomography (64-MDCT) is a major concern for physicians and patients alike. A new 320 row area detector computed tomography (ADCT) can obtain a view of the entire heart with one rotation (0.35 s) without requiring the helical method. As such, ADCT is expected to reduce the radiation dose. We studied image quality and radiation dose of ADCT compared to that of 64-MDCT in patients with a low heart rate (HR≤60). METHODS: Three hundred eighty-five consecutive patients underwent 64-MDCT and 379 patients, ADCT. Patients with an arrhythmia were excluded. Prospective ECG-gated helical scan with high HP (FlashScan) in 64 was used for MDCT and prospective ECG-gated conventional one beat scan, for 320-ADCT. Image quality was visually evaluated by an image quality score. Radiation dose was estimated by DLP (mGyï½¥cm) for 64-MDCT and DLP.e (mGyï½¥cm) for 320-ADCT. RESULTS: Radiation dose of 320-ADCT (208±48 mGyï½¥cm) was significantly (P<0.0001) lower than that of 64-MDCT (484±112 mGyï½¥cm), and image quality score of 320-ADCT (3.0±0.2) was significantly (P=0.0011) higher than that of 64-MDCT (2.9±0.4). Scan time of 320-ADCT (1.4±0.1 s) was also significantly (P<0.0001) shorter than that of 64-MDCT (6.8±0.6 s). CONCLUSIONS: 320-ADCT can achieve not only a reduction in radiation dose but also a superior image quality and shortening of scan time compared to 64-MDCT.

[What factors affected image quality in coronary multidetector-row computed tomography?].

BACKGROUND: Although it is well known that we usually cannot acquire a high quality coronary MDCT in patients with arrhythmia or incomplete breath-hold, we sometimes also cannot obtain a high quality coronary MDCT in patients without arrhythmia or incomplete breath-hold. PURPOSE: We studied what factors other than arrhythmia or incomplete breath-hold affected image quality. METHODS: Coronary MDCT and echocardiography were performed within one month in 2145 patients, and 452 cases of arrhythmia or 102 cases of incomplete breath-hold during scanning were eliminated. The remaining 1591 patients were studied. Those patients were divided into two groups (mid-diastolic phase reconstruction (MD) group (N=1377) and end-systolic phase reconstruction (ES) group (N=214)). Age, body weight, mean heart rate (HR) during scanning, temporal resolution (TR) and left ventricular ejection fraction (LVEF) by echocardiography were estimated. Image quality (A: Excellent (3 points), B: Acceptable (2 points), C: Unacceptable (1 point)) was evaluated. RESULTS: The mean image quality points of the MD group (2.9±0.3) were significantly (P<0.0001) higher than the mean image quality points of the ES group (2.3±0.7), and the mean HR of the MD group (57±6 bpm) was significantly (P<0.0001) lower than that of the ES group (81±15 bpm). In the MD group, HR and TR were selected as significant factors affecting image quality by stepwise regression analysis. In the ES group, TR and HR were selected. In the ES subgroup with HR<90 bpm, TR and HR were selected; however, in the ES subgroup with HR≥90 bpm, TR and LVEF were selected. CONCLUSION: In the MD group, low HR was important for high quality coronary MDCT. In the ES subgroup with HR<90, short TR and low HR were important; however, in the ES subgroup with HR≥90 bpm, TR and LVEF were more important than HR.

[A new acquisition method with pacemaker resetting of coronary multidetector-row computed tomography for reduction of radiation dose in patients with pacemaker].

We proposed a new acquisition method of coronary MDCT achieved by pacing rate resetting and/or propranolol or verapamil injection in patients with a pacemaker. Coronary MDCT was undertaken in 57 patients with a pacemaker (DDD: 51, VVI: 6) and in 2975 patients with sinus rhythm as control using Aquilion 64 (Toshiba). Pacing rate was reset to 60 beats per minute (bpm) in DDD, and spontaneous beats were suppressed by propranolol injection. Pacing rate was reset to 70 bpm in atrial fibrillation with VVI, and spontaneous beats were suppressed by verapamil injection. Coronary MDCT was undertaken using as high a beam pitch (BP) as possible. When spontaneous beats were not suppressed, we selected the optimal gantry speed and BP to get the highest temporal resolution. Image quality makes no significant difference between pacemaker and sinus rhythm. When spontaneous beats were completely suppressed (all pacing), mean radiation dose and acquisition time, respectively, decreased by 33.0% and 35.2% in DDD compared with the method recommended by Heart Navi (by Toshiba), and they decreased by 38.1% and 25.9%, respectively, in VVI compared with the method recommended by Heart Navi. We could not estimate coronary stenosis in the proximal right coronary artery by lead artifacts in 30% of DDD pacemakers. In conclusion, the new method is useful for not only reducing radiation dose and acquisition time, but also for maintaining image quality in patients with a pacemaker.