High-Pitch, Low-Voltage and Low-Iodine-Concentration CT Angiography of Aorta: Assessment of Image Quality and Radiation Dose with Iterative Reconstruction

Objective: To assess the image quality of aorta obtained by dual-source computed tomography angiography (DSCTA), performed with high pitch, low tube voltage, and low iodine concentration contrast medium (CM) with images reconstructed using iterative reconstruction (IR). Methods: One hundred patients randomly allocated to receive one of two types of CM underwent DSCTA with the electrocardiogram-triggered Flash protocol. In the low-iodine group, 50 patients received CM containing 270 mg I/mL and were scanned at low tube voltage (100 kVp). In the high-iodine CM group, 50 patients received CM containing 370 mg I/mL and were scanned at the tube voltage (120 kVp). The filtered back projection (FBP) algorithm was used for reconstruction in both groups. In addition, the IR algorithm was used in the low-iodine group. Image quality of the aorta was analyzed subjectively by a 3-point grading scale and objectively by measuring the CT attenuation in terms of the signal- and contrast-to-noise ratios (SNR and CNR, respectively). Radiation and CM doses were compared.Results: The CT attenuation, subjective image quality assessment, SNR, and CNR of various aortic regions of interest did not differ significantly between two groups. In the low-iodine group, images reconstructed by FBP and IR demonstrated significant differences in image noise, SNR, and CNR (p<0.05). The low-iodine group resulted in 34.3% less radiation (4.4 ± 0.5 mSv) than the high-iodine group (6.7 ± 0.6 mSv), and 27.3% less iodine weight (20.36 ± 2.65 g) than the high-iodine group (28 ± 1.98 g). Observers exhibited excellent agreement on the aortic image quality scores (κ = 0.904). Conclusions: CT images of aorta could be obtained within 2 s by using a DSCT Flash protocol with low tube voltage, IR, and low-iodine-concentration CM. Appropriate contrast enhancement was achieved while maintaining good image quality and decreasing the radiation and iodine doses

Divisive Gain Modulation with Dynamic Stimuli in Integrate-and-Fire Neurons

The modulation of the sensitivity, or gain, of neural responses to input is an important component of neural computation. It has been shown that divisive gain modulation of neural responses can result from a stochastic shunting from balanced (mixed excitation and inhibition) background activity. This gain control scheme was developed and explored with static inputs, where the membrane and spike train statistics were stationary in time. However, input statistics, such as the firing rates of pre-synaptic neurons, are often dynamic, varying on timescales comparable to typical membrane time constants. Using a population density approach for integrate-and-fire neurons with dynamic and temporally rich inputs, we find that the same fluctuation-induced divisive gain modulation is operative for dynamic inputs driving nonequilibrium responses. Moreover, the degree of divisive scaling of the dynamic response is quantitatively the same as the steady-state responses—thus, gain modulation via balanced conductance fluctuations generalizes in a straight-forward way to a dynamic setting

Coronary computed tomography - present status and future directions

The use of coronary computed tomography angiography (cCTA) is growing rapidly, in large part because of fast-paced technical innovations that have increased diagnostic accuracy while providing new opportunities for radiation dose reduction. cCTA using recent generation CT scanners has been repeatedly shown to have excellent negative predictive value for ruling out significant coronary stenosis in comparison with invasive coronary angiography (ICA) and is now accepted for this use in selected populations. Current work is increasingly focused on evaluating and optimising radiation dose reduction techniques, the cost-effectiveness of cCTA implementation, and the impact of cCTA on patient management and outcomes. In addition, the potential value of emerging applications, such as atherosclerotic plaque characterisation and myocardial perfusion and viability assessment, are undergoing intense investigation

High-pitch low-voltage CT coronary artery calcium scoring with tin filtration: accuracy and radiation dose reduction

Objectives: To investigate diagnostic accuracy and radiation dose of high-pitch CT coronary artery calcium scoring (CACS) with tin filtration (Sn100kVp) versus standard 120kVp high-pitch acquisition. Methods: 78 patients (58% male, 61.5±9.1 years) were prospectively enrolled. Subjects underwent clinical 120kVp high-pitch CACS using third-generation dual-source CT followed by additional high-pitch Sn100kVp acquisition. Agatston scores, calcium volume scores, Agatston score categories, percentile-based risk categorization and radiation metrics were compared. Results: 61/78 patients showed coronary calcifications. Median Agatston scores were 34.9 [0.7–197.1] and 41.7 [0.7–207.2] and calcium volume scores were 34.1 [0.7–218.0] for Sn100kVp and 35.7 [1.1–221.0] for 120kVp acquisitions, respectively (both p&lt;0.0001). Bland-Altman analysis revealed underestimated Agatston scores and calcium volume scores with Sn100kVp versus 120kVp acquisitions (mean difference: 16.4 and 11.5). However, Agatston score categories and percentile-based risk categories showed excellent agreement (ĸ=0.98 and ĸ=0.99). Image noise was 25.8±4.4HU and 16.6±2.9HU in Sn100kVp and 120kVp scans, respectively (p&lt;0.0001). Dose-length-product was 9.9±4.8mGy*cm and 40.9±14.4mGy*cm with Sn100kVp and 120kVp scans, respectively (p&lt;0.0001). This resulted in significant effective radiation dose reduction (0.13±0.07mSv vs. 0.57±0.2mSv, p&lt;0.0001) for Sn100kVp acquisitions. Conclusion: CACS using high-pitch low-voltage tin-filtered acquisitions demonstrates excellent agreement in Agatston score and percentile-based cardiac risk categorization with standard 120kVp high-pitch acquisitions. Furthermore, radiation dose was significantly reduced by 78% while maintaining accurate risk prediction. Key points: • Coronary artery calcium scoring with tin filtration reduces radiation dose by 78%. • There is excellent correlation between high-pitch Sn100kVp and standard 120kVp acquisitions. • Excellent agreement regarding Agatston score categories and percentile-based risk categorization was achieved. • No cardiac risk reclassifications were observed using Sn100kVp coronary artery calcium scoring

Automated quantification of epicardial adipose tissue using CT angiography: evaluation of a prototype software.

This study evaluated the performance of a novel automated software tool for epicardial fat volume (EFV) quantification compared to a standard manual technique at coronary CT angiography (cCTA).cCTA data sets of 70 patients (58.6 ± 12.9 years, 33 men) were retrospectively analysed using two different post-processing software applications. Observer 1 performed a manual single-plane pericardial border definition and EFVM segmentation (manual approach). Two observers used a software program with fully automated 3D pericardial border definition and EFVA calculation (automated approach). EFV and time required for measuring EFV (including software processing time and manual optimization time) for each method were recorded. Intraobserver and interobserver reliability was assessed on the prototype software measurements. T test, Spearman's rho, and Bland-Altman plots were used for statistical analysis.The final EFVA (with manual border optimization) was strongly correlated with the manual axial segmentation measurement (60.9 ± 33.2 mL vs. 65.8 ± 37.0 mL, rho = 0.970, P  0.9).Automated EFVA quantification is an accurate and time-saving method for quantification of EFV compared to established manual axial segmentation methods.• Manual epicardial fat volume quantification correlates with risk factors but is time-consuming. • The novel software prototype automates measurement of epicardial fat volume with good accuracy. • This novel approach is less time-consuming and could be incorporated into clinical workflow

Coronary artery calcium in breast cancer survivors after radiation therapy

The purpose of the current study is to investigate whether breast cancer survivors after radiation therapy have a higher burden of coronary artery calcium as a potential surrogate of radiation-induced accelerated coronary artery disease. 333 patients were included. 54 patients underwent chest CT ae 6 months after the start of radiation therapy (radiation therapy group), while 279 patients had a CT scan either prior to or without undergoing radiation therapy (RT). Coronary artery calcium was quantified from CT by applying a threshold-based automated algorithm. Mean age at diagnosis was similar (p = 0.771) between RT (57.4 +/- 13.1 years) and NoRT (58.0 +/- 11.9 years). Median time between radiation therapy and CT was 2 years. The groups showed no significant differences in race, smoking history, cancer laterality, or cancer stage. 39 (72.2%) of RT patients had a coronary artery calcium score of 0, compared to 201 (72.0%) in patients without radiation therapy. Median coronary artery calcium burden for both groups was not significantly different (p = 0.982), nor when comparing patients who underwent left- versus right-sided radiation therapy (p = 0.453). When adjusting for the time between diagnosis and CT, radiation therapy patients had a significantly lower risk of a positive coronary artery calcium score. In conclusion, breast cancer survivors after radiation therapy are not more likely to show coronary artery calcium on follow-up CT imaging. Our results thus do not support radiation-induced accelerated coronary artery disease as an explanation for higher rates of heart disease in this group

Computed Tomography-Derived Parameters of Myocardial Morphology and Function in Black and White Patients With Acute Chest Pain

Blacks have higher mortality and hospitalization rates because of congestive heart failure compared with white counterparts. Differences in cardiac structure and function may contribute to the racial disparity in cardiovascular outcomes. Our aim was to compare computed tomography (CT) derived cardiac measurements between black patients with acute chest pain and age- and gender-matched white patients. We performed a retrospective analysis under an institutional review board waiver and in Health Insurance. Portability and Accountability Act compliance. We investigated patients who underwent cardiac dual-source CT for acute chest pain. Myocardial mass, left ventricular (LV) ejection fraction, LV end-systolic volume, and LV end-diastolic volume were quantified using an automated analysis algorithm. Septal wall thickness and cardiac chamber diameters were manually measured. Measurements were compared by independent t test and linear regression. The study population consisted of 300 patients (150 black mean age 54 +/- 12 years; 46% men; 150 white mean. age 55 +/- 11 years; 46% men). Myocardial mass was larger for blacks compared with white (176.1 +/- 58.4 vs 155.9 +/- 51.7 g, p = 0.002), which remained significant after adjusting for age, gender, body mass index, and hypertension. Septal wall thickness was slightly greater (11.9 +/- 2.7 vs 11.2 +/- 3.1 mm, p =.0.036). The LV inner diameter was moderately larger in black patients in systole (32.3 +/- 9.0 vs 30.1 +/- 5.4 ml, p = 0.010) and in diastole (50.1 +/- 7.8 vs 48.9 +/- 5.2 ml, p = 0.137), as well as LV end-diastolic volume (134.5 +/- 42.7 vs 128.2 +/- 30.6 ml, p = 0.143). Ejection fraction was nonsignificantly lower in blacks. (67.1 +/- 13.5% vs 69.0 +/- 9.6%, p = 0.169). In conclusion, CT-derived myocardial mass was larger in blacks compared with whites, whereas LV functional parameters were generally not statistically different, suggesting that LV mass might be a possible contributing factor to the higher rate of cardiac events in blacks. (C) 2016 Elsevier Inc. All rights reserved