Tomonari Sano

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.

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.

Significance of PQ interval in acquisition of coronary multidetector row computed tomography

BACKGROUND Since image quality obtained in the mid-diastolic [or slow filling (SF)] phase is generally superior to end-systolic image in coronary multidetector row computed tomography (MDCT), low heart rate (HR) comprises the most important factor for acquisition of high-quality images. However, despite HR <70 and optimum breath-hold, sometimes high quality images cannot be obtained in SF. We assessed the significance of PQ interval in acquisition of coronary MDCT. METHODS AND RESULTS Of 541 consecutive patients who underwent coronary MDCT, 7 patients with incomplete breath-hold, 62 HR ≥70, and 70 arrhythmias were excluded. The remaining 402 patients (M: 222, 66±11 years), including 38 with first-degree atrioventricular block (1° AVB, PQ >200 ms) were evaluated. RR and PQ were measured on electrocardiogram and systolic and SF phase with 4-chamber cine cardiac computed tomography. SF significantly (p<0.0001) correlated with RR (SF=-471+0.720RR, r=0.887) in all subjects. The SF of without 1° AVB (292±97 ms) was significantly (p<0.0147) longer than that of with 1° AVB (251±121 ms), although RR was not significantly different between the two groups. The SF/RR of without 1° AVB (27.2±6.1%) was also significantly (p<0.0001) higher than that of with 1° AVB (22.7±8.0%). The coefficient of correlation between (RR-PQ) and SF [r=0.915, p<0.0001, SF=-362+0.742(RR-PQ)] was significantly (p<0.034) higher than that of correlation between RR and SF in all subjects. The SF of rank A image quality was significantly longer than that of rank B (p<0.0001) or rank C (p=0.0042). In critical HR (60-69 bpm), the optimum phase was ES in 7/139 patients without 1° AVB, and SF in 3/13 patients with 1° AVB (chi(2), p<0.0416). CONCLUSION Since SF depends on (RR-PQ), if PQ is long in critical HR, it might be difficult to reconstruct high quality images in the SF phase.

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.

Evaluation of exposure dose reduction in multislice CT coronary angiography (MS-CTA) with prospective ECG-gated helical scan

A novel low-dose ECG-gated helical scan method to investigate coronary artery diseases was developed. This method uses a high pitch for scanning (based on the patients heart rate) and X-rays are generated only during the optimal cardiac phases. The dose reduction was obtained using a two-level approach: 1) To use a 64-slice CT scanner (Aquilion, Toshiba, Otawara, Tochigi, Japan) with a scan speed of 0.35 s/rot. to helically scan the heart at a high pitch based on the patients heart rate. By changing the pitch from the conventional 0.175 to 0.271 for a heart rate of 60 bpm, the exposure dose was reduced to 65%. 2) To employ tube current gating that predicts the timing of optimal cardiac phases from the previous cardiac cycle and generates X-rays only during the required cardiac phases. The combination of high speed scanning with a high pitch and appropriate X-ray generation only in the cardiac phases from 60% to 90% allows the exposure dose to be reduced to 5.6 mSv for patients with a heart rate lower than 65 bpm. This is a dose reduction of approximately 70% compared to the conventional scanning method recommended by the manufacturer when segmental reconstruction is considered. This low-dose protocol seamlessly allows for wide scan ranges (e.g., aortic dissection) with the benefits of ECG-gated helical scanning: smooth continuity for longitudinal direction and utilization of data from all cardiac cycles.

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.

320-ADCT(0.275 s/rot)による冠動脈CT 血管造影におけるハーフ再構成，体動補正ソフト(APMC)およびフル再構成の限界(RR-PQ)時間

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 β-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.

Single injection protocol for coronary and lower extremity CT angiographies in patients suspected for peripheral arterial disease

AbstractTo evaluate the feasibility of a single injection protocol for coronary CT angiography (CTA) and lower extremity CTA in patients suspected for peripheral arterial disease (PAD).This prospective observational study included a total of 103 patients who showed an ankle brachial index ⩽0.9 and underwent the single injection protocol for coronary and lower extremity CTA. All CTAs used iodinated contrast (weight × 0.06 mL/s × 20 seconds). A prospective Electrocardiogram (ECG)-gated coronary CTA was performed, followed by helical lower extremity CTA beginning 9 seconds after coronary CTA. Using catheter angiography as reference standard, diagnostic ability of CTA was evaluated.The mean total volume of iodinated contrast used was 70 ± 14 mL. Contrast opacification in the superficial femoral artery was adequate (408 ± 97  Hounsfield Units [HU]) and PAD was detected in 72.8% (75/103). The estimated radiation doses for lower extremity and coronary CTA were 3.6 ± 1.2 and 5.5 ± 4.5 mSv. A significant coronary stenosis was detected in 47 patients (45.6%). Coronary CT image quality was recorded as excellent in 86.4%, acceptable in 11.7%, and unacceptable for 1.9%. Contrast opacification within the superficial femoral artery was adequate in all cases while 27.2% needed an additional scan below the calf to capture the contrast bolus arrival in the smaller lower extremity vessels. Segment based sensitivity, specificity, positive, and negative predictive values were 57.9%, 97.9%, 73.8%, and 95.9% for the coronary CTA, and 63.4%, 91.5%, 76.3%, and 85.3% for peripheral CTA.A single injection protocol for coronary CTA and lower extremity CTA is feasible with a relatively small volume of iodinated contrast.