Evaluation of fibrotic liver disease with whole-liver T1ρ MR imaging: a feasibility study at 1.5 T.

PURPOSE: To test at 1.5 T whether T1ρ magnetic resonance (MR) imaging of fibrotic liver disease is feasible, to investigate whether liver T1ρ imaging allows assessment of the severity of liver cirrhosis, and to assess the normal liver T1ρ range in healthy patients. MATERIALS AND METHODS: This prospective study was approved by the institutional ethics committee. Written informed consent was obtained. Healthy volunteers (n = 25) and patients (n = 34) with cirrhosis underwent whole-liver T1ρ MR imaging at 1.5 T. Mean T1ρ values were calculated from liver regions of interest. Mean T1ρ values were correlated to clinical data and histopathologic analysis by analysis of variance. Receiver operating characteristic curves were calculated to determine the accuracy of mean T1ρ values for the assessment of Child-Pugh class. RESULTS: Mean T1ρ values of volunteers (mean, 40.9 msec ± 2.9 [standard deviation]; range, 33.9-46.3 msec) were significantly lower than those of patients who were Child-Pugh class A (P < .004), B (P < .001), or C (P < .001), and significant differences were found between each Child-Pugh stage (A vs B, P < .002; B vs C, P < .009; A vs C, P < .001). Liver cirrhosis was confirmed via histologic analysis in all patients with liver biopsy. Mean T1ρ values did not correlate with necroinflammatory activity (r = 0.31; P = .23), degree of steatosis (r = -0.016; P = .68), or presence of iron load (r = 0.22; P = .43). Mean T1ρ values performed well by assessing the Child-Pugh stage, with receiver operating characteristic areas of 0.95-0.98. Intraclass correlation coefficient values ranged between 0.890 and 0.987, which indicated excellent imaging and reimaging reproducibility and interobserver and intraobserver variability. CONCLUSION: Whole-liver T1ρ MR imaging at 1.5 T to detect and assess human liver cirrhosis is feasible. Further investigation and optimization of this technique are warranted to cover the entire spectrum of fibrotic liver disease.

Cardiac structure and function in response to a multi-stage marathon over 4486 km.

AIMS: To investigate whether participation in the Trans Europe Foot Race 2009 (TEFR), an ultramarathon race held over 64 consecutive days and 4486 km, led to changes in cardiac structure and function. METHODS: Cardiac magnetic resonance imaging was performed in 20 of 67 participating runners (two women; mean ± SD age 47.8 ± 10.4 years) at three time points (baseline scan at 294 ± 135 km (B), scan two at 1735 ± 86 km (T1) and scan three at 3370 ± 90 km (T2)) during the TEFR. Imaging included an assessment of left ventricular structure (mass) and function (strain). In parallel, cardiac troponin I, NT-pro-BNP, myostatin and GDF11 were determined in venous blood samples. A subsample of ten runners returned for a follow-up scan eight months after the race. RESULTS: Left ventricular mass increased significantly (B, 158.5 ± 23.8 g; T1, 165.1 ± 23.2 g; T2, 167 ± 24.6 g; p < 0.001) over the course of the race, although no significant change was seen in the remaining structural and functional parameters. Serum concentrations of cardiac troponin I and NT-proBNP significantly increased 1.5 - and 3.5-fold, respectively, during the first measurement interval, with no further increase thereafter (cardiac troponin I, 6.8 ± 3.1 (B), 16.9 ± 10.4 (T1) and 17.1 ± 9.7 (T2); NT-proBNP, 30.3 ± 22.8 (B), 135.9 ± 177.5 (T1) and 111.2 ± 87.3 (T2)), whereas the growth markers myostatin and GDF11 did not change. No association was observed with functional parameters, including the ejection fraction and the volume of both ventricles. The follow-up scans showed a reduction to baseline values (left ventricular mass 157 ± 19.3 g). CONCLUSIONS: High exercise-induced cardiac volume load for >2 months in ultra-endurance runners results in a physiological structural adaptation with no sign of adverse cardiovascular remodelling.

Non-invasive determination of pressure recovery by cardiac MRI and echocardiography in patients with severe aortic stenosis: short and long-term outcome prediction.

OBJECTIVE: To assess the influence of pressure recovery (PR)-corrected haemodynamic parameters on outcome in patients with aortic stenosis. METHODS: Aortic stenosis severity parameters were corrected for PR (increase in static pressure due to decreasing dynamic pressure), assessed using transthoracic echocardiography (TTE) or cardiac magnetic resonance imaging (CMR), in patients with aortic stenosis. PR, indexed PR (iPR) and energy loss index (ELI) were determined. Factors that predicted all-cause mortality, and 9-month or 10-year New York Heart Association classification ≥2 were assessed using Cox proportional hazards regression. RESULTS: A total of 25 patients, aged 68 ± 10 years, were included. PR was 17 ± 6 mmHg using CMR, and CMR correlated with TTE measurements. PR correction using CMR data reduced the AS-severity classification in 12-20% of patients, and correction using TTE data reduced the AS-severity classification in 16% of patients. Age (Wald 4.774) was a statistically significant predictor of all-cause mortality; effective orifice area (Wald 3.753) and ELI (Wald 3.772) almost reached significance. CONCLUSIONS: PR determination may result in significant reclassification of aortic stenosis severity and may hold value in predicting all-cause mortality.

Extent of size, shape and systolic variability of the left ventricular outflow tract in aortic stenosis determined by phase-contrast MRI.

PURPOSE: Left ventricular outflow tract (LVOT) dimensions are important for calculation of aortic valve areas and planning of valve repair. Mostly, LVOT areas are calculated from echocardiographic longitudinal measurements with the assumption of a round shape. Here, orthogonal phase contrast (PC) MRI with dynamic assessment of LVOT was compared to standard longitudinal cine MRI and 2D echocardiography. METHODS: In 19 patients with aortic stenosis (5 female; 69±10years), LVOT areas were determined on orthogonal PC images, either by planimetry (Aplan) or by two-diameter measurement (Aellip). Data were analyzed in early, middle and late systole (t1/t2/t3). Additionally, standard diameter-based calculation (A3CV) of LVOT on longitudinal three-chamber view (3CV) MRI images and 2D echocardiography was performed. RESULTS: Calculated PC LVOT areas strongly correlated to planimetry (r=0.95; p<0.001) with almost identical areas (Aplan 5.1±1.1cm2 vs. Aellip 5.3±1.0cm2). In PC changes of LVOT-eccentricity during systole were most pronounced in late systole (t1 vs. t3plan -7.4±18%). Cine 3CV calculation resulted in lower LVOT areas compared to Aplan (A3CV 3.7±0.9cm2; p<0.001), yet correlating to Aplan (r=0.66; p=0.002). 3CV LVOT areas correlated to echocardiography (r=0.56; p=0.014). CONCLUSIONS: Calculated LVOT areas seem to be sufficient for daily routine. Compared to the orthogonal view, standard long-axis 3CV underestimates the LVOT size and overestimates the systolic reduction of LVOT-size. Systolic changes are most pronounced in late systole.

Hemodynamic assessment of severe aortic stenosis: MRI evaluation of dynamic changes of vena contracta.

PURPOSE: Direct magnetic resonance imaging (MRI) planimetry of the maximal systolic aortic valve area does not consider temporal variations of the opening area during the ejection period. We evaluated an MRI-based methodology for the assessment of valvular dynamics in patients with severe aortic stenosis by measuring the systolic variability of the valvular blood stream, that is, the "vena contracta." MATERIALS AND METHODS: With institutional review board approval, we examined 22 patients (13 male, 9 female; mean age, 68 ±10 years) with severe aortic stenosis using 1.5 T MRI and a standardized scanning protocol consisting of gradient-echo phase-contrast velocity imaging and steady-state free precession-cine MRI before and after valve replacement therapy. Temporal changes of the aortic valve area, represented by systolic variations of the area of poststenotic turbulent flow at its smallest convergence, that is, the proximal vena contracta, were determined by MRI and quantified by a calculated parameter of temporal valve dynamics (T). T was defined as the period which the aortic valve spent over its maximal opening area (>85%) during systole. MRI was also used to determine left ventricular hypertrophy before (LVMI) and its regression (LVMR) after valve replacement. Findings were compared with transthoracic echocardiography and cardiac catheterization. RESULTS: All patients had an echocardiographic effective orifice area, EOATTE, of <1.0 cm2. The comparison of T to LVMI and LVMR revealed significant correlations (LVMI: r = -0.62; P = 0.002; LVMR: r = 0.62; P = 0.002). Further significant correlations with aortic stenosis severity were observed in the comparison with manual planimetry, invasive measurements, and echocardiographic valve areas, as well as with pressure gradients. CONCLUSIONS: MRI can measure systolic variations of the aortic valve area. Quantitative parameters of the hemodynamic relevance of valve dynamics obtained by this method correlate with established parameters of aortic stenosis severity and LVMR.