PurposeTo validate three widely‐used acceleration methods in four‐dimensional (4D) flow cardiac MR; segmented 4D‐spoiled‐gradient‐echo (4D‐SPGR), 4D‐echo‐planar‐imaging (4D‐EPI), and 4D‐k‐t Broad‐use Linear Acquisition Speed‐up Technique (4D‐k‐t BLAST).Materials and MethodsAcceleration methods were investigated in static/pulsatile phantoms and 25 volunteers on 1.5 Tesla MR systems. In phantoms, flow was quantified by 2D phase‐contrast (PC), the three 4D flow methods and the time‐beaker flow measurements. The later was used as the reference method. Peak velocity and flow assessment was done by means of all sequences. For peak velocity assessment 2D PC was used as the reference method. For flow assessment, consistency between mitral inflow and aortic outflow was investigated for all pulse‐sequences. Visual grading of image quality/artifacts was performed on a four‐point‐scale (0 = no artifacts; 3 = nonevaluable).ResultsFor the pulsatile phantom experiments, the mean error for 2D PC = 1.0 ± 1.1%, 4D‐SPGR = 4.9 ± 1.3%, 4D‐EPI = 7.6 ± 1.3% and 4D‐k‐t BLAST = 4.4 ± 1.9%. In vivo, acquisition time was shortest for 4D‐EPI (4D‐EPI = 8 ± 2 min versus 4D‐SPGR = 9 ± 3 min, P < 0.05 and 4D‐k‐t BLAST = 9 ± 3 min, P = 0.29). 4D‐EPI and 4D‐k‐t BLAST had minimal artifacts, while for 4D‐SPGR, 40% of aortic valve/mitral valve (AV/MV) assessments scored 3 (nonevaluable). Peak velocity assessment using 4D‐EPI demonstrated best correlation to 2D PC (AV:r = 0.78, P < 0.001; MV:r = 0.71, P < 0.001). Coefficient of variability (CV) for net forward flow (NFF) volume was least for 4D‐EPI (7%) (2D PC:11%, 4D‐SPGR: 29%, 4D‐k‐t BLAST: 30%, respectively).ConclusionIn phantom, all 4D flow techniques demonstrated mean error of less than 8%. 4D‐EPI demonstrated the least susceptibility to artifacts, good image quality, modest agreement with the current reference standard for peak intra‐cardiac velocities and the highest consistency of intra‐cardiac flow quantifications. Level of Evidence: 1 Technical Efficacy: Stage 2J. Magn. Reson. Imaging 2018;47:272–281.

Recently, the determination of S-phenylmercapturic acid (S-PMA) in urine has been proposed as a suitable biomarker for the monitoring of low level exposures to benzene. In the study reported here, the test has been validated in 12 separate studies in chemical manufacturing plants, oil refineries, and natural gas production plants. Parameters eight hour exposure to airborne benzene of 1 mg/m3 (0 3 ppm) and higher and urinary S-PMA concentrations in end of shift samples. It was calculated that an eight hour benzene exposure of 3-25 mg/m3 (1 ppm) corresponds to an average S-PMA concentration of 46 pg/g creatinine (95% confidence interval 41-50 pg/g creatinine). A strong correlation was also found between urinary phenol and S-PMA concentrations. At a urinary phenol concentration of 50 mg/g creatinine, corresponding to an eight hour benzene exposure of 32-5 mg/m' (10 ppm), the average urinary S-PMA concentration was 383 ug/g creatinine. In conclusion, with the current sensitivity of the test, eight hour time weighted average benzene exposures of 1 mg/m' (0 3 ppm) and higher can be measured.

Purpose: To evaluate the accuracy and reproducibility of aortic pulse wave velocity (PWV) assessment by in-plane velocity-encoded magnetic resonance imaging (MRI). Materials and Methods:In 14 patients selected for cardiac catheterization on suspicion of coronary artery disease and 15 healthy volunteers, PWV was assessed with multislice two-directional in-plane velocity-encoded MRI (PWV i.p. ) and compared with conventionally assessed PWV from multisite one-directional through-plane velocityencoded MRI (PWV t.p. ). In patients, PWV was also obtained from intraarterially acquired pressure-time curves (PWV pressure ), which is considered the gold standard reference method. In volunteers, PWV i.p. and PWV t.p. were obtained in duplicate in the same examination to test reproducibility. Conclusion: PWV i.p. is an improvement over conventional PWV t.p. by showing higher agreement as compared to the gold standard (PWV pressure ) and higher reproducibility for repeated MRI assessment.

Streamline visualization of 4DFlow MRI data revealed dynamic trans-LAVV inflow and more lateral flow after AVSD correction. Streamline visualization improved trans-LAVV flow quantification as the positioning and angulation of the measurement plane was optimized, allowing an accurate assessment of left ventricular inflow.

To compare four-dimensional flow MRI with automated valve tracking to manual valve tracking in patients with acquired or congenital heart disease and healthy volunteers. Materials and Methods: In this retrospective study, data were collected from 114 patients and 46 volunteers who underwent fourdimensional flow MRI at 1.5 T or 3.0 T from 2006 through 2017. Among the 114 patients, 33 had acquired and 81 had congenital heart disease (median age, 17 years; interquartile range [IQR], 13-49 years), 51 (45%) were women, and 63 (55%) were men. Among the 46 volunteers (median age, 28 years; IQR, 22-36 years), there were 19 (41%) women and 27 (59%) men. Two orthogonal cine views of each valve were used for valve tracking. Wilcoxon signed-rank test was used to compare analysis times, net forward volumes (NFVs), and regurgitant fractions. Intra-and interobserver variability was tested by using intraclass correlation coefficients (ICCs). Results: Analysis time was shorter for automated versus manual tracking (all patients, 14 minutes [IQR, 12-15 minutes] vs 25 minutes [IQR, 20-25 minutes]; P , .001). Although overall differences in NFV and regurgitant fraction were comparable between both methods, NFV variation over four valves was smaller for automated versus manual tracking (all patients, 4.9% [IQR, 3.3%-6.7%] vs 9.8% [IQR, 5.1%-14.7%], respectively; P , .001). Regurgitation severity was discordant for seven pulmonary valves, 22 mitral valves, and 21 tricuspid valves. Intra-and interobserver agreement for automated tracking was excellent for NFV assessment (intra-and interobserver, ICC  0.99) and strong to excellent for regurgitant fraction assessment (intraobserver, ICC  0.94; interobserver, ICC  0.89). Conclusion: Automated valve tracking reduces analysis time and improves reliability of valvular flow quantification with fourdimensional flow MRI in patients with acquired or congenital heart disease and in healthy volunteers.

Regional PWV was significantly increased in MFS patients as compared to healthy volunteers within similar age range, in all aortic segments except the ascending aorta. Furthermore, regional PWV-assessment has moderate to high specificity for predicting absence of regional aortic luminal growth for all aortic segments in MFS patients.

PWV-leveling between aorta and carotid artery at older age is associated with a reduction in blood flow volume towards the brain. Velocity-encoded MRI can be used to evaluate PWV and flow volume distribution in the aortic arch and the carotid circulation.

Purpose: To study age-related change in aortic stiffness in patients with Marfan syndrome (MFS) versus healthy volunteers using velocity-encoded (VE) MRI.Materials and Methods: Twenty-five MFS patients (age range, 18-63 years; mean age 36 6 14 years, 13 men) and 25 age-/gender-matched healthy volunteers were examined with VE-MRI. Aortic stiffness was expressed by pulse wave velocity (PWV), assessed in the proximal and distal part of the aorta and in the total aorta. PWV was compared between patients and volunteers and age-relation was determined by linear regression.Results: PWV was significantly higher in all parts of the aorta in patients when compared with healthy volunteers (proximal aorta 5.7 6 1.5 m/s versus 4.8 6 0.9 m/s, distal aorta 6.4 6 2.4 m/s versus 5.0 6 1.2 m/s and total aorta 5.9 6 1.7 m/s versus 4.9 6 1.1 m/s, all P < 0.004). PWV correlated significantly with age (Pearson R between 0.45 and 0.94). Only in the proximal aorta, the increase in PWV with age was significantly higher in patients (7 6 2 cm/s increase with age) than in volunteers (3 6 1 cm/s increase, P ¼ 0.03); in the distal or total aorta, the increase in PWV with age was not different between patients and volunteers.Conclusion: Velocity-encoded MRI detects more pronounced age-related aortic stiffening in the proximal aorta in MFS patients versus healthy volunteers, suggesting more severe wall disease in MFS.