Contrast volume reduction using third generation dual source computed tomography for the evaluation of patients prior to transcatheter aortic valve implantation.

OBJECTIVES: Chronic renal failure is common in patients referred for transcatheter aortic valve implantation (TAVI). CT angiography is recommended and provides crucial information prior to TAVI. We evaluated the feasibility of a reduced contrast volume protocol for pre-procedural CT imaging. METHODS: Forty consecutive patients were examined with prospectively ECG-triggered high-pitch spiral acquisition using a novel third-generation dual-source CT system; 38 ml contrast agent was used. Image quality was graded on a visual scale (1-4). Contrast attenuation was measured at the level of the aortic root and at the iliac bifurcation. RESULTS: Mean patient age was 82 ± 6 years (23 males; 58 %). Mean attenuation/average image quality was 285 ± 60 HU/1.5 at the aortic annulus compared to 289 ± 74 HU/1.8 at the iliac bifurcation (p = 0.77/p = 0.29). Mean estimated effective radiation dose was 2.9 ± 0.3 mSv. A repeat acquisition was necessary in one patient due to image quality. Out of the 35 patients who underwent TAVI, 31 (89 %) patients had no or mild aortic regurgitation. Thirty-two (91 %) patients were discharged successfully. CONCLUSION: Pre-procedural CTA with a total of 38 ml contrast volume is feasible and clinically useful, using third-generation dual-source CT, allowing comprehensive imaging for procedural success. KEY POINTS: • Reduction of contrast agent volume is crucial in patients with chronic renal failure. • Novel third-generation computed tomography helps to reduce contrast agent volume. • Pre-procedural CT allows comprehensive imaging for procedural success before heart valve implantation. • A low-contrast CT protocol is feasible for pre-procedural TAVI planning.

Epicardial fat and coronary artery calcification in patients on long-term hemodialysis.

INTRODUCTION: Recent studies have shown a significant correlation between increased epicardial fat volume (EFV) and mortality, coronary artery disease events, and measures of coronary atherosclerotic burden, for example, coronary calcium. Patients with chronic kidney disease on hemodialysis have an increased prevalence of coronary atherosclerosis and coronary calcium. The mechanisms underlying both may differ from patients with normal kidney function. Only limited data are available on the relationship between epicardial fat and coronary calcium in these patients. METHODS: Ninety-three consecutive patients (62 men and 31 women; mean age, 55 ± 11 years) with chronic kidney failure on regular hemodialysis underwent computed tomography for coronary calcium scoring as well as assessment of cardiovascular risk factors. Calcium scoring was performed using a low-dose, prospectively ECG-triggered high pitch spiral acquisition protocol (dual-source computed tomography, 280-millisecond (ms) rotation, 2 × 128 × 0.6-mm collimation, 120-kV tube voltage, 80-mA·s tube current). Cross-sectional images were reconstructed with 3.0-mm thickness, 1.5-mm increment, and a medium sharp reconstruction kernel (B35f). Agatston score and EVF were analyzed in a semiautomatic fashion using dedicated software. RESULTS: The mean duration of dialysis was 5.7 years. Of all patients, 93% had arterial hypertension, 66% had hyperlipidemia, 30% were diabetic, and 49.5% were current or prior smokers. The mean body mass index (BMI) was 27 ± 4 kg/m. The mean EFV was 162 ± 80 mL, and the mean coronary artery calcification (CAC) was 765 ± 1391 Agatston units (AU). In univariable and multivariable analysis, EFV was significantly correlated to BMI (P < 0.05) and age (P = 0.021), but not to CAC (P = 0.106). In subanalysis for values binned by median, we also found a significant correlation between EFV (binned) and smoking (P = 0.49) as well as a significant correlation between EFV (binned) and CAC for 46 patients younger than 55 years (median age). CONCLUSION: The epicardial fat volume in patients with chronic kidney disease and on hemodialysis is significantly correlated to BMI, age, and smoking but, with the exception of younger patients, not to the coronary calcium score. Our data suggest that in this special patient cohort, other mechanisms might influence the genesis of coronary calcification.

Image quality of ultra-low radiation exposure coronary CT angiography with an effective dose <0.1 mSv using high-pitch spiral acquisition and raw data-based iterative reconstruction.

OBJECTIVES: We evaluated the potential of prospectively ECG-triggered high-pitch spiral acquisition with low tube voltage and current in combination with iterative reconstruction to achieve coronary CT angiography with sufficient image quality at an effective dose below 0.1 mSv. METHODS: Contrast-enhanced coronary dual source CT angiography (2 × 128 × 0.6 mm, 80 kV, 50 mAs) in prospectively ECG-triggered high-pitch spiral acquisition mode was performed in 21 consecutive individuals (body weight <100 kg, heart rate ≤60/min). Images were reconstructed with raw data-based filtered back projection (FBP) and iterative reconstruction (IR). Image quality was assessed on a 4-point scale (1 = no artefacts, 4 = unevaluable). RESULTS: Mean effective dose was 0.06 ± 0.01 mSv. Image noise was significantly reduced in IR (128.9 ± 46.6 vs. 158.2 ± 44.7 HU). The mean image quality score was lower for IR (1.9 ± 1.1 vs. 2.2 ± 1.0, P < 0.0001). Of 292 coronary segments, 55 in FBP and 40 in IR (P = 0.12) were graded "unevaluable". In patients with a body weight ≤75 kg, both in FBP and in IR, the rates of fully evaluable segments were significantly higher in comparison to patients >75 kg. CONCLUSIONS: Coronary CT angiography with an estimated effective dose <0.1 mSv may provide sufficient image quality in selected patients through the combination of high-pitch spiral acquisition and raw data-based iterative reconstruction.

Patient-specific predictors of image noise in coronary CT angiography.

BACKGROUND: Coronary computed tomography (CT) angiography can be associated with high radiation exposure. Reduction of tube voltage from 120 kV to 100 kV can reduce the dose by up to 40%, but it also increases image noise. OBJECTIVE: We aimed to find a patient-specific predictor of image noise to determine the use of reduced tube voltage. METHODS: Contrast-enhanced coronary dual-source CT angiography data sets [prospectively electrocardiogram (ECG)-triggered axial and retrospectively ECG-gated spiral acquisition, rotation of 280 milliseconds, 2 × 128 × 0.6 mm collimation, 100 kV, 320 mAs] of 165 patients (age, 54 ± 13 years) for the detection of coronary artery stenoses were analyzed. Image noise was measured in the aortic root. Influence of body weight, height, body mass index, thoracic cross sectional area, as well as the area of the thoracic solid tissue were analyzed. RESULTS: Mean image noise in the aorta was 35.1 ± 8.9 HU. Mean dose length product was 207 ± 184 cm · cGy with an average effective dose of 2.9 ± 2.6 mSv. The patient cohort was divided into tertiles according to image noise. Numerous parameters, including BMI and body weight, were significantly different between the highest and lowest tertiles. In multivariable regression analysis, the area of the thoracic solid tissue was the only independent predictor of image noise (P < 0.0001). CONCLUSIONS: The area of the thoracic solid tissue at the level of the aortic root predicts image noise and may hence be used for the decision to reduce tube voltage from 120 kV to 100 kV.