[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.