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Objective To determine the optimal reconstruction phase and acquisition time window of coronary computed tomography angiography (CCTA) in patients with different heart rates based on prospective ECG-gating and to compare the image quality and radiation dose between the whole cardiac cycle mode and optimized acquisition time window. Materials and methods One thousand patients(536male, mean age ± standard deviation, 57.43 ± 11.73years) who underwent CCTA were divided into two groups, group A ( n  = 500)and group B( n  = 500). According to the heart rate at the time of CCTA, the subjects were divided into subgroups A1 and B1 (< 51 bpm), A2 and B2 subgroups (51–55 bpm), A3 and B3 subgroups (56–60 bpm), A4 and B4 subgroups (61–65 bpm), A5 and B5 subgroups (66–70 bpm), A6 and B6 subgroups (71–75 bpm), A7 and B7 subgroups (76–80 bpm), and A8 and B8 subgroups (81–85 bpm), A9 and B9 subgroups (> 85 bpm). Group A individuals underwent CCTA within a single cardiac cycle and the optimal reconstruction phase at each heart rate was identified based on image quality. The ideal acquisition time window was determined by considering the 95% confidence interval of the best reconstruction phase, which was equivalent to the average value of the best reconstruction phase (standard deviation × 2). The individuals in group B were examined within the optimal collection time window. Compare the radiation doses and image quality of patients in groups A and B. Results The findings indicated that the A1-A9 subgroups’ optimal reconstruction phase and acquisition time window were: 61%~85% RR interval; 68%~84% RR interval;70%~82% RR interval and 34%~46% RR interval; 70%~82%RR interval, and 34%~46% RR interval;70%~82% RR interval and 36%~48% RR interval; 65%~89% RR interval and 38%~50% RR interval;68%~84% RR interval and 36%~56%RR interval; 38%~54% RR interval; 38%~58% RR interval. No statistically significant difference was observed in terms of Signal-to-Noise Ratio(SNR), and Contrast-to-Noise Ratio(CNR) between group A and group B, ( P  > 0.05). The average effective radiation dose(ED) values in Group B were 42.6%, lower than in Group A, ( P  < 0.001). Conclusions Ideal acquisition phase and acquisition-time windows vary among individuals with varying heart rate(HR). Narrowing the acquisition timeframe based on prospective electrocardiogram(ECG)-gating can considerably lower the radiation dose of CCTA imaging while maintaining image quality.

Objectives To assess the effect of lower volumes of contrast medium (CM) on image quality in high-pitch dual-source computed tomography coronary angiography (CTCA). Methods One-hundred consecutive patients (body weight 65–85 kg, stable heart rate ≤65 bpm, cardiac index ≥2.5 L/min/m 2 ) referred for CTCA were prospectively enrolled. Patients were randomly assigned to one of five groups of different CM volumes (G 30 , 30 mL; G 40 , 40 mL; G 50 , 50 mL; G 60 , 60 mL; G 70 , 70 mL; flow rate 5 mL/s each, iodine content 370 mg/mL). Attenuation within the proximal and distal coronary artery segments was analysed. Results Mean attenuation for men and women ranged from 345.0 and 399.1 HU in G 30 to 478.2 and 571.8 HU in G 70 . Mean attenuation values were higher in groups with higher CM volumes ( P  < 0.0001) and higher in women than in men ( P  < 0.0001). The proportions of segments with attenuation of at least 300 HU in G 30 , G 40 , G 50 , G 60 and G 70 were 89 %, 95 %, 98 %, 98 % and 99 %. CM volume of 30 mL in women and 40 mL in men proved to be sufficient to guarantee attenuation of at least 300 HU. Conclusions In selected patients high-pitch dual-source CTCA can be performed with CM volumes of 40 mL in men or 30 mL in women. Key Points • High - pitch dual - source coronary angiography is feasible with low contrast media volumes . • Traditional injection rules still apply : higher volumes result in higher enhancement . • The patient ’ s gender is a co - factor determining the level of contrast enhancement . • Volumes can be reduced down to 30 – 40 mL in selected patients .

Objective To investigate the feasibility of applying prospectively ECG-triggered sequential coronary CT angiography (CCTA) to patients with atrial fibrillation (AF) and evaluate the image quality and radiation dose compared with a retrospectively ECG-gated helical protocol. Methods 100 patients with persistent AF were enrolled. Fifty patients were randomly assigned to a prospective protocol and the other patients to a retrospective protocol using a second-generation dual-source CT (DS-CT). Image quality was evaluated using a four-point grading scale (1 = excellent, 2 = good, 3 = moderate, 4 = poor) by two reviewers on a per-segment basis. The coronary artery segments were considered non-diagnostic with a quality score of 4. The radiation dose was evaluated. Results Diagnostic segment rate in the prospective group was 99.4 % (642/646 segments), while that in the retrospective group was 96.5 % (604/626 segments) ( P  < 0.001). Effective dose was 4.29 ± 1.86 and 11.95 ± 5.34 mSv for each of the two protocols ( P  < 0.001), which was a 64 % reduction in the radiation dose for prospective sequential imaging compared with retrospective helical imaging. Conclusion In AF patients, prospectively ECG-triggered sequential CCTA is feasible using second-generation DS-CT and can decrease >60 % radiation exposure compared with retrospectively ECG-gated helical imaging while improving diagnostic image quality. Key Points • Coronary computed tomographic angiography (CCTA) can be difficult in patients with arrhythmias. • Prospectively ECG-triggered sequential CCTA is feasible in patients with atrial fibrillation. • Prospective sequential imaging can improve quality compared with retrospective analysis. • Prospective sequential imaging decreases radiation exposure by 64 % compared with retrospective mode.

Introduction This study aimed to evaluate the feasibility of non-contrast-enhanced 4D magnetic resonance angiography (NCE 4D MRA) with signal targeting with alternative radiofrequency (STAR) spin labeling and variable flip angle (VFA) sampling in the assessment of dural arteriovenous fistula (DAVF) in the transverse sinus. Methods Nine patients underwent NCE 4D MRA for the evaluation of DAVF in the transverse sinus at 3 T. One patient was examined twice, once before and once after the interventional treatment. All patients also underwent digital subtraction angiography (DSA) and/or contrast-enhanced magnetic resonance angiography (CEMRA). For the acquisition of NCE 4D MRA, a STAR spin tagging method was used, and a VFA sampling was applied in the data readout module instead of a constant flip angle. Two readers evaluated the NCE 4D MRA data for the diagnosis of DAVF and its type with consensus. The results were compared with those from DSA and/or CEMRA. Results All patients underwent NCE 4D MRA without any difficulty. Among seven patients with patent DAVFs, all cases showed an early visualization of the transverse sinus on NCE 4D MRA. Except for one case, the type of DAVF of NCE 4D MRA was agreed with that of reference standard study. Cortical venous reflux (CVR) was demonstrated in two cases out of three patients with CVR. Conclusion NCE 4D MRA with STAR tagging and VFA sampling is technically and clinically feasible and represents a promising technique for assessment of DAVF in the transverse sinus. Further technical developments should aim at improvements of spatial and temporal coverage.

Objective To evaluate staged low-dose approaches for coronary CT angiography (CTA) in which a standard sequence was added if the low-dose sequence did not allow reliable rule-out of coronary stenosis. Patients and Methods A total of 176 consecutive patients referred for dual-source CTA were randomized to three protocols: group 1 using prospective ECG-triggering (100 kV, 330 mAs), group 2 a retrospectively gated “MinDose” sequence (100 kV, 330 mAs) and group 3 a standard spiral sequence (120 kV, 400 mAs). If image quality in low-dose groups 1 or 2 was non-diagnostic, an additional standard CT examination (as in group 3) was performed. Results Non-diagnostic image quality was found in 11/56, 4/55, and 2/65 patients (46/896, 4/880 and 3/1,040 coronary segments) in groups 1, 2 and 3, respectively. Median (interquartile ranges) volumes of contrast material, CTDI vol , DLP and effective dose for low-dose groups 1 and 2 and for standard group 3 were 92.5 (11.3), 75.0 (2.5) and 75.0 (9.0) ml; 8.0 (1.4), 16.8 (4.8) and 48.1 (14.2) mGy; 108.0 (27.3), 246.0 (93.0) and 701.0 (207.8) mGy cm; and 1.5 (0.4), 3.4 (1.3) and 9.8 (2.9) mSv, respectively. Conclusion A staged coronary CTA protocol with an initial low-dose approach and addition of a standard sequence—should image quality be too low—can lead to a substantial reduction in radiation exposure.

Background We compared the interobserver variability concerning the detection of calcified and non-calcified plaque in two different low-dose and standard retrospectively gated protocols for coronary CTA. Methods 150 patients with low heart rates and less than 100 kg body weight were randomised and examined by contrast-enhanced dual-source CT coronary angiography (100 kV, 320 mAs). 50 patients were examined with prospectively ECG-triggered axial acquisition, 50 patients with prospectively ECG-triggered high pitch spiral acquisition, and 50 patients using spiral acquisition with retrospective ECG gating. Two investigators independently analysed the datasets concerning the presence of calcified and non-calcified plaque on a per-segment level. Results Mean effective dose was 1.4 ± 0.2 mSv for axial, 0.8 ± 0.07 mSv for high-pitch spiral, and 5.3 ± 2.6 mSV for standard spiral acquisition ( P  < 0.0001). In axial acquisition, interobserver agreement concerning the presence of atherosclerotic plaque was achieved in 650/749 coronary segments (86.8%). In high-pitch spiral acquisition, agreement was achieved in 664/748 segments (88.8%, n.s.). In standard spiral acquisition, agreement was achieved in 672/738 segments (91.0%, P  < 0.0001). Interobserver agreement was significantly higher for calcified than for non-calcified plaque in all data acquisition modes. Conclusion Low-dose coronary CT angiography permits the detection of coronary atherosclerotic plaque with good interobserver agreement. Key Points • Low-dose CT protocols permit coronary plaque detection with good interobserver agreement. • Image noise is a major predictor of interobserver variability. • Interobserver agreement is significantly higher for calcified than for non-calcified plaque.

The purpose of this study was to investigate the value of brain ventricular wall movement assessment with a gated cine trueFISP MR sequence for the diagnosis of endoscopic third ventriculostomy (ETV) patency. Sixteen healthy volunteers and ten consecutive patients with noncommunicating hydrocephalus were explored with a MR scanner (Siemens, Avanto 1.5 T) before, 1 week and 3 months after ETV. TrueFISP was evaluated qualitatively (ventricular wall movement and CSF flow through ETV) and quantitatively [distance moved (DMLT) during a cardiac cycle by the lamina terminalis]. The third ventricle volume (TVV) was assessed. Statistical analysis was performed using nonparametric tests. There was no motion of the lamina terminalis (LT) detected on preoperative data. A pulsatile motion of the LT was found for patients with a patent ETV and for controls. DMLT and TVV were correlated (r = 0.79, P = 0.006). A transient dysfunction of ETV was successfully diagnosed on the trueFISP sequence with no motion of the LT or CSF flow observed. The trueFISP sequence appears reliable for the diagnosis of ETV patency and provides non-invasive assessment of the movement of the ventricular wall related to CSF pressure changes.

Cerebrospinal fluid (CSF) dynamics have been mostly studied with cardiac-gated phase contrast MRI combining signal from many cardiac cycles to create cine-phase sampling of one time-averaged cardiac cycle. The relative effects of cardiac and respiratory changes on CSF movement are not well understood. There is possible respiration-driven movement of CSF in ventricles, cisterns, and subarachnoid spaces which has not been characterized with velocity measurements. To date, commonly used cine-phase contrast techniques of velocity imaging inherently cannot detect respiratory velocity changes since cardiac-gated data acquired over several minutes randomizes respiratory phase contributions. We have developed an extremely fast, real-time, and quantitative MRI technique to image CSF velocity in simultaneous multi-slice (SMS) echo planar imaging (EPI) acquisitions of 3 or 6 slice levels simultaneously over 30s and observe 3D spatial distributions of CSF velocity. Measurements were made in 10 subjects utilizing a respiratory belt to record respiratory phases and visual cues to instruct subjects on breathing rates. A protocol is able to measure velocity within regions of brain and basal cisterns covered with 24 axial slices in 4minutes, repeated for 3 velocity directions. These measurements were performed throughout the whole brain, rather than in selected line regions so that a global view of CSF dynamics could be visualized. Observations of cardiac and breathing-driven CSF dynamics show bidirectional respiratory motion occurs primarily along the central axis through the basal cisterns and intraventricular passageways and to a lesser extent in the peripheral Sylvian fissure with little CSF motion present in subarachnoid spaces. During inspiration phase, there is upward (inferior to superior) CSF movement into the cranial cavity and lateral ventricles and a reversal of direction in expiration phase. •Real-time imaging of CSF velocity cardiac and respiratory components•Novel technique is simultaneous multi-slice (SMS) phase contrast (PC) EPI•Respiratory driven CSF velocity for the first time is observed in direction and magnitude•Inspiration phase CSF movement is directed upwards through the foramen magnum into the basal cisterns and into the ventricular system.•Expiration phase direction is reversed giving bidirectional respiratory motion

Objectives To validate an artificial intelligence (AI)–based fully automatic coronary artery calcium (CAC) scoring system on non-electrocardiogram (ECG)–gated low-dose chest computed tomography (LDCT) using multi-institutional datasets with manual CAC scoring as the reference standard. Methods This retrospective study included 452 subjects from three academic institutions, who underwent both ECG-gated calcium scoring computed tomography (CSCT) and LDCT scans. For all CSCT and LDCT scans, automatic CAC scoring (CAC_auto) was performed using AI-based software, and manual CAC scoring (CAC_man) was set as the reference standard. The reliability and agreement of CAC_auto was evaluated and compared with that of CAC_man using intraclass correlation coefficients (ICCs) and Bland-Altman plots. The reliability between CAC_auto and CAC_man for CAC severity categories was analyzed using weighted kappa ( κ ) statistics. Results CAC_auto on CSCT and LDCT yielded a high ICC (0.998, 95% confidence interval (CI) 0.998–0.999 and 0.989, 95% CI 0.987–0.991, respectively) and a mean difference with 95% limits of agreement of 1.3 ± 37.1 and 0.8 ± 75.7, respectively. CAC_auto achieved excellent reliability for CAC severity ( κ = 0.918–0.972) on CSCT and good to excellent but heterogenous reliability among datasets ( κ = 0.748–0.924) on LDCT. Conclusions The application of an AI-based automatic CAC scoring software to LDCT shows good to excellent reliability in CAC score and CAC severity categorization in multi-institutional datasets; however, the reliability varies among institutions. Key Points • AI-based automatic CAC scoring on LDCT shows excellent reliability with manual CAC scoring in multi-institutional datasets. • The reliability for CAC score–based severity categorization varies among datasets. • Automatic scoring for LDCT shows a higher false-positive rate than automatic scoring for CSCT, and most common causes of a false-positive are image noise and artifacts for both CSCT and LDCT.

Purpose We evaluated low-contrast injection protocols for coronary computed tomography angiography (CTA) using a 64-detector scanner and the test bolus technique. Materials and methods We randomly assigned 60 patients undergoing coronary CTA to one of two contrast material (CM) injection protocols. For the lowcontrast dose protocol (P low ), the patients received injections of iohexol-350 [0.7 ml/kg body weight (BW)] during 9 s, and the test-bolus technique was used. Under the conventional protocol (P conv ), they received iohexol-350 (1.0 ml/kg BW) during 15 s, and bolus tracking was used. We compared the protocols for attenuation values in the ascending aorta and coronary arteries and for the amount of CM required. Results There was no significant difference in the mean CT attenuation of the ascending aorta and coronary arteries between the P low and P conv groups. The amount of CM was significantly less with P low than with P conv [49.7 ± 6.4 ml (main bolus: 39.7 ± 6.4 ml) vs. 57.0 ± 10.1 ml, P < 0.01]. Conclusion With 64-detector CTA of the heart, the low-dose and short-injection-duration protocol with the test-injection technique provides vessel attenuation comparable to that obtained with the standard-dose protocol with the bolus-tracking technique.