[Coronary Computed Tomography Angiography for Patients with Atrial Fibrillation: Feasibility of Prospective Electrocardiography-gated Diastolic Acquisition with a Manual Exposure-termination Technique].

Coronary computed tomography angiography (CCTA) was performed in 283 patients with atrial fibrillation (Af) using a prospective electocardiogeaphic gated scanning with a manual exposure-termination technique. When preparatory 5-beat scanning contained at least one RR interval longer than 800 ms, 5-beat diastolic scanning (R+800 ms protocol) was selected. When no RR interval longer than 800 ms was observed, 2-beat scanning starting at end-systolic phase (R+210 ms to R protocol) was chosen. In R+800 ms protocol, we manually terminated scanning when motion free real-time reconstruction image was confirmed. R+800 ms protocol was applied in 95% of the cases and required an average of 2 cardiac cycles, providing motion-free images in 91% of the patients. The mean exposure dose was less than that with R+210 ms to R protocol. Using the protocols above, 90% of the all patients with Af provided motion free images and 99% of them were evaluable.

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.

Assessment of coronary in-stent restenosis: value of subtraction coronary computed tomography angiography.

In conventional coronary computed tomography angiography (CCTA), metal artifacts are frequently observed where stents are located, making it difficult to evaluate in-stent restenosis. This study was conducted to investigate whether subtraction CCTA can improve diagnostic accuracy in the evaluation of in-stent restenosis. Subtraction CCTA was performed using 320-row CT in 398 patients with previously placed stents who were able to hold their breath for 25 s and in whom mid-diastolic prospective one-beat scanning was possible. Among these patients, 126 patients (94 men and 32 women, age 74 ± 8 years) with 370 stents who also underwent invasive coronary angiography (ICA) were selected as the subjects of this study. With ICA findings considered the gold standard, conventional CCTA was compared against subtraction CCTA to determine whether subtraction can improve diagnostic accuracy in the evaluation of in-stent restenosis. When non-assessable stents were considered to be stenotic, the diagnostic accuracy in the evaluation of in-stent restenosis was 62.7 % for conventional CCTA and 89.5 % for subtraction CCTA. When the non-assessable stents were considered to be non-stenotic the diagnostic accuracy was 90.3 % for conventional CCTA and 94.31 % for subtraction CCTA. When subtraction CCTA was used to evaluate only the 138 stents that were judged to be non-assessable by conventional CCTA, 116 of these stents were judged to be assessable, and the findings for 109 of them agreed with those obtained by ICA. Even for stents with an internal diameter of 2.5-3 mm, the lumen can be evaluated in more than 80 % of patients. Subtraction CCTA provides significantly higher diagnostic accuracy than conventional CCTA in the evaluation of in-stent restenosis.

Subtraction coronary computed tomography in patients with severe calcification.

To investigate the clinical usefulness of subtraction coronary computed tomographic angiography (CCTA) in patients with severe calcification. A 320-row area detector CT system was used in this study. The subjects were 78 patients (47 men and 31 women, 739 years of age) with an Agatston score of >300 who were able to undergo prospective one-beat scanning during a single breath-hold. The CCTA findings were compared against invasive coronary angiography. The diagnostic capabilities of CCTA for the severely calcified segments with and without the additional information provided by subtraction CCTA were compared. Severe calcification was observed in 174 (31.9%) of the 546 segments, and non-assessable regions were observed in 74 (13.6%) of the segments. The addition of subtraction CCTA information improved the diagnostic accuracy for segments with severe calcification from 67.8 to 82.8% on a per-segment basis and from 70.1 to 82.1% on a per-patient basis, with non-assessable segments considered to be stenotic. When non-assessable segments were considered to be an incorrect diagnosis, the diagnostic accuracy was improved from 48.3 to 75.9% on a per-segment basis and from 43.3 to 79.1% on a per-patient basis. In addition, when evaluation was limited to non-assessable segments, subtraction CCTA provided a diagnostic accuracy of 81.1% when non-assessable segments were considered to be stenotic or 66.2% when non-assessable segments were considered to be an incorrect diagnosis. Subtraction CCTA improves the diagnostic capabilities of CCTA in patients with severe calcification.

[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.

Segmental distributions of calcifications and non-assessable lesions on coronary computed tomographic angiography: evaluation in symptomatic patients.

PURPOSE: To clarify the frequency and distribution pattern of calcifications in all and in only non-assessable coronary arterial segments in symptomatic patients with coronary heart disease. MATERIALS AND METHODS: Among 2355 consecutive coronary CT angiographies performed using a 320-row ADCT, 1129 studies performed by prospective one-beat scanning without metallic and motion artifacts were evaluated. Frequency and degree of calcification were assessed for each coronary segment. Evaluations were performed in all and in only non-assessable segments, and the results were compared. RESULTS: Calcified segments were observed in 15.6 % of patients and 2.4 % of segments. The most extensively calcified segments were those in the proximal left anterior descending branch. 1.1 % of all of the segments were not assessable due to calcification, and 90 % of those non-assessable segments had high-grade calcifications. When the calcium score value was 1000 or 2000, the expected frequency of non-assessable segments was 27.5 or 53.5 %, respectively. CONCLUSION: There were specific features of the distribution of coronary arterial calcifications. It is important to be familiar with these features when deciding whether or not to perform subtraction CCTA.

Overestimation of pretest probability of coronary artery disease by Duke clinical score in patients undergoing coronary CT angiography in a Japanese population.

BACKGROUND: The Duke clinical score (DCS) is commonly used to estimate the pretest probability of coronary artery disease (CAD). However, the criterion was developed in a population undergoing catheter angiography. OBJECTIVE: To test the hypothesis that DCS overestimates the CAD probability when applied to patients evaluated with coronary CT angiography (CCTA). A second objective is to compute an adjustment of the calculated DCS to apply to this population. METHODS: The DCS was calculated for the 3996 consecutive CCTA studies (February 2009 to April 2013) performed for symptomatic patients with no known CAD. Performance of the DCS for the detection of CAD was evaluated by the area under the receiver operating characteristic curve. Using the training cohort (n = 2789), a linear regression line between the calculated probability and the observed prevalence of CAD identified a modified DCS cutoff for a better risk categorization; this was internally validated by a separate cohort (n = 1207). RESULTS: The DCS showed a good discrimination (area under the receiver operating characteristic curve = 0.71) for the detection of CAD (prevalence = 23.3%). The calibration analysis showed an overall 2.4-fold overestimation by DCS with a DCS < 23% corresponding to the low-risk category (ie, observed prevalence of CAD < 10%). There was no appropriate DCS cutoff to define high-risk category (ie, prevalence > 90%). The validation cohort showed a prevalence of 9.4% when DCS < 23% was used to define low risk. CONCLUSION: Among patients who underwent CCTA, DCS overestimated the pretest probability by at least 2-fold; the DCS < 23% should define the lower risk probability. The DCS poorly identifies high-risk population and thus development of new CCTA-based criteria is warranted.

[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.

[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.

[Reconstruction of coronary 64-multidetector-row computed tomography angiography in patients with atrial fibrillation: delete short RR intervals using electorocardiogram].

BACKGROUND: The image qualities of coronary 64-multidetector-row computed tomography angiography (CCTA) in patients with atrial fibrillation (Afib) are often not enough. This study clarifies how to use electrocardiogram (ECG) -editing in Afib. METHODS: We performed CCTA (Aquilion 64 with beam pitch: 0.125, 0.35 s/r) in 33 patients (M/F=24/9, age: 71±9 yr, mean heart rate: 71±12 bpm) with Afib. We injected 5 mg of verapamil into the vein when the mean HR was ≥80 bpm. First, we reconstructed images after deleting short RR (<800, 750, 700, 650, or 600). Second, we reconstructed images in 4 different methods: (1) end-systolic images with Phase Navi (automatically selecting an optimal phase) (ES-Navi), (2) Mid-diastolic images with Phase Navi (MD-Navi), (3) Mid-diastolic images reconstructed by the "R+absolute time method" [Edit-MD (R+)], and (4) Mid-diastolic images reconstructed by the "R-absolute time method" [Edit-MD (R-)]. We reconstructed 1 and 2 without ECG-editing, and 3 and 4 were reconstructed after ECG-editing without a data deficit. The quality of the images was classified into 3 ranks: no artifact (3), mild artifact (2), and severe artifact (1). RESULTS: The image quality point of CCTA, reconstructed after deleting RR<750, was similar to RR<800, and RR<750 was even higher than that after deleting HR<600, 650, or 700. The mean image quality point of CCTA that was reconstructed by Edit-MD (R-) or Edit-MD (R+) was significantly higher than ES-Navi or MD-Navi. CONCLUSION: The high image quality of CCTA could be reconstructed after deleting RR<750 in 76% or after deleting RR<800 in 70% of Afib. The reconstruction using Edit-MD (R-) or Edit-MD (R+) without a data deficit could provide a better quality CCTA than using PhaseNavi in Afib.

Prevalence of computed tomographic angiography-verified high-risk plaques and significant luminal stenosis in patients with zero coronary calcium score.

BACKGROUND: Some patients were detected with coronary artery disease even if the coronary artery calcium score was (CACS)=0. We evaluated the prevalence and predictor of significant stenosis and computed tomography (CT) based vulnerable plaque (CTVP) for patients with CACS=0. METHODS: Subjects were 2160 patients (M/F=1110/1050, 64.7 ± 11.6 years) who underwent measurement of calcium score and CT coronary angiography. As for CACS=0 group, age, gender, coronary risk factor (family history (FH), hypertension (HT), hyperlipidemia (HL), diabetes (DM), and smoking), body mass index, history of cerebral infarction, the presence of chest symptom, and abnormal rest ECG findings were investigated as predictors for significant stenosis and CTVP by multivariate analysis using logistic regression analysis. RESULTS: Out of 2160 patients, 1141 (52.8%, M/F=655/486, 68.4 ± 9.8 years) were of CACS>0 and 1019 (47.2%, M/F=455/564, 60.5 ± 12.0 years) were of CACS=0. In the CACS=0 group, 24 patients (2.4%) were found with significant stenosis and 47 (4.6%) with 2FPP. In 104 patients with spotty calcification (10.2%), 10 (9.6%) out of these 104 had significant stenosis and also had CTVP. Multivariate analysis using logistic regression analysis revealed significant predictor for significant stenosis to be only male (Odds ratio (OR): 3.075, 95%CI 1.166-8.109, p=0.0232) and significant predictor for CTVP to be age (OR: 1.032, 95%CI 1.001-1.063, p=0.0437) and male (OR: 2.386, 95%CI 1.193-4.775, p=0.0140). CONCLUSIONS: The present study suggests that the presence of CTVP must be noted, when patients are male and elderly even if CACS=0 and the presence of spotty calcification increases the prevalence of significant stenosis and CTVP in patients with CACS=0.

[Estimation of radiation dose and image quality of coronary 320-row area detector CT angiography by optimal prospective ECG-gated protocols for different heart rate].

The purpose of this study is to estimate radiation dose and image quality of ECG-gated coronary 320-area detector CT (ADCT) angiography which was acquired using the protocols that were considered as optimal methods for different heart rates (HR) in 1031 consecutive patients (M/F=580/451, 65 ± 12 yr) without arrhythmias. We set up 5 protocols for 320-ADCT based on the relationship among heart rates, temporal resolution, gantry rotation speed, optimal reconstruction phase and slow filling phase on 64-multidetector-row computed tomography (MDCT), ie, 1) mid-diastolic (75% of RR) 1 beat scan (MD 1 beat, N=761(73.8%)) for HR ≤ 60, 2) mid-diastolic (75% of RR) 2 beat scan (MD 2 beat, N=135) for 61 ≤ HR ≤ 65, 3) end-systolic and mid-diastolic (37-80% of RR) 2 beat scan (ES-MD 2 beat, N=92) for 66 ≤ HR ≤ 75, 4) end-systolic (R+280-430 ms) 2 beat scan (ES 2 beat, N=21) for 76 ≤ HR ≤ 80, and 5) end-systolic (R+250-400 ms) 3 beat scan (ES 3 beat, N=22) for 81 ≤ HR ≤ 105. Image quality was classified into 3 categories (excellent (3 points), acceptable (2 points), and unacceptable (1 point)). Scanning time, DLP.e and image quality score were 1.4 ± 0.1 s, 220 ± 59 mGy·cm, 3.0 ± 0.2 points in MD 1 beat, 2.2 ± 0.2 s, 434 ± 118 mGy·cm, 2.9 ± 0.3 points in MD 2 beat, 2.1 ± 0.2 s, 729 ± 229 mGy·cm, 2.7 ± 0.5 points in ES-MD 2 beat, 1.9 ± 0.1 s, 432 ± 148 mGy·cm, 2.2 ± 0.6 points in ES 2 beat, and 2.4 ± 0.2 s, 669 ± 152 mGy·cm, 2.3 ± 0.6 points in ES 3 beat respectively. In conclusion, the prospective ECG-gated scan protocol for coronary 320-ADCT angiography in any HR group was considered reasonable and proper for image quality and radiation dose.

[Relationship among RR interval, optimal reconstruction phase, temporal resolution, and image quality of end-systolic reconstruction of coronary CT angiography in patients with high heart rates: in search of the optimal acquisition protocol].

The purpose of this study is to elucidate the relationship among RR interval (RR), the optimal reconstruction phase, and adequate temporal resolution (TR) to obtain coronary CT angiography images of acceptable quality using 64-MDCT (Aquilion 64) of end-systolic reconstruction in 407 patients with high heart rates. Image quality was classified into 3 groups [rank A (excellent): 161, rank B (acceptable): 207, and rank C (unacceptable): 39 patients]. The optimal absolute phase (OAP) significantly correlated with RR [OAP (ms)=119-0.286RR (ms), r=0.832, p<0.0001], and the optimal relative phase (ORP) also significantly correlated with RR [ORP (%)=62-0.023RR (ms), r=0.656, p<0.0001], and the correlation coefficient of OAP was significantly (p<0.0001) higher than that of ORP. The OAP range (±2SD) in which it is highly possible to get a static image was from [119-0.286RR (ms)-46] to [119-0.286RR (ms)+46]. The TR was significantly different among ranks A (97 ± 22 ms), B (111 ± 31 ms) and C (135 ± 34 ms). The TR significantly correlated with RR in ranks A (TR=-16+0.149RR, r=0.767, p<0.0001), B (TR=-15+0.166RR, r=0.646, p<0.0001), and C (TR=52+0.117RR, r=0.425, p=0.0069). Rank C was distinguished from ranks A or B by linear discriminate analysis (TR=-46+0.21RR), and the discriminate rate was 82.6%. In conclusion, both the OAP and adequate TR depend on RR, and the OAP range (±2SD) can be calculated using the formula [119-0.286RR (ms)-46] to [119-0.286RR (ms)+46], and an adequate TR value would be less than (-46+0.21RR).

[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.

[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

[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.

[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.