Right and left ventricle native T1 mapping in systolic phase in patients with congenital heart disease

Background T1 mapping is emerging as a powerful tool in cardiac magnetic resonance (CMR) to evaluate diffuse fibrosis. However, right ventricular (RV) T1 mapping proves difficult due to the limited wall thickness in diastolic phase. Several studies focused on systolic T1 mapping, albeit only on the left ventricle (LV). Purpose To estimate intra- and inter-observer variability of native T1 (nT1) mapping of the RV, and its correlations with biventricular and pulmonary function in patients with congenital heart disease (CHD). Material and Methods In this retrospective, observational, cross-sectional study we evaluated 36 patients with CHD, having undergone CMR on a 1.5-T scanner. LV and RV functional evaluations were performed. A native modified look-locker inversion recovery short-axis sequence was acquired in the systolic phase. Intra- and inter-reader reproducibility were reported as complement to 100% of the ratio between coefficient of reproducibility and mean. Spearman rho and Mann-Whitney U-test were used to compare distributions. Results Intra- and inter-reader reproducibility was 84% and 82%, respectively. Median nT1 was 1022 ms (interquartile range [IQR] 1108-972) for the RV and 947 ms (IQR 986-914) for the LV. Median RV-nT1 was 1016 ms (IQR 1090-1016) in patients with EDVI <= 100 mL/m(2) and 1100 ms (IQR 1113-1100) in patients with EDVI >100 mL/m(2) (P = 0.049). A significant negative correlation was found between RV ejection fraction and RV-nT1 (rho = -0.284, P = 0.046). Conclusion Systolic RV-nT1 showed a high reproducibility and a negative correlation with RV ejection fraction, potentially reflecting an adaptation of the RV myocardium to pulmonary valve/conduit (dys)-function

Variability and homogeneity of cardiovascular magnetic resonance myocardial T2-mapping in volunteers compared to patients with edema

BACKGROUND: The aim of the study was to test the reproducibility and variability of myocardial T2 mapping in relation to sequence type and spatial orientation in a large group of healthy volunteers. For control T2 mapping was also applied in patients with true edema. Cardiovascular magnetic resonance (CMR) T2-mapping has potential for the detection and quantification of myocardial edema. Clinical experience is limited so far. The variability and potential pitfalls in broad application are unknown. METHODS: Healthy volunteers (n = 73, 35 +/- 13 years) and patients with edema (n = 28, 55 +/- 17 years) underwent CMR at 1.5 T. Steady state free precession (SSFP) cine loops and T2-weighted spin echo images were obtained. In patients, additionally late gadolinium enhancement images were acquired. We obtained T2 maps in midventricular short axis (SAX) and four-chamber view (4CV) based on images with T2 preparation times of 0, 24, 55 ms and compared fast low angle shot (FLASH) and SSFP readout. 10 volunteers were scanned twice on separate days. Two observers analysed segmental and global T2 per slice. RESULTS: In volunteers global myocardial T2 systematically differed depending on image orientation and sequence (FLASH 52 +/- 5 vs. SSFP 55 +/- 5 ms in SAX and 57 +/- 6 vs. 59 +/- 6 ms in 4CV; p /= 70 ms. Mean intraobserver variability was 1.07 +/- 1.03 ms (r = 0.94); interobserver variability was 1.6 +/- 1.5 ms (r = 0.87). The coefficient of variation for repeated scans was 7.6% for SAX and 6.6% for 4CV. Mapping revealed focally increased T2 (73 +/- 9 vs. 51 +/- 3 ms in remote myocardium; p < 0.0001) in all patients with edema. CONCLUSIONS: Myocardial T2 mapping is technically feasible and highly reproducible. It can detect focal edema und differentiate it from normal myocardium. Increased T2 was found in some volunteers most likely due to partial volume and residual motion

Aortic valve stenotic area calculation from phase contrast cardiovascular magnetic resonance: the importance of short echo time

<p>Abstract</p> <p>Background</p> <p>Cardiovascular magnetic resonance (CMR) can potentially quantify aortic valve area (AVA) in aortic stenosis (AS) using a single-slice phase contrast (PC) acquisition at valve level: AVA = aortic flow/aortic velocity-time integral (VTI). However, CMR has been shown to underestimate aortic flow in turbulent high velocity jets, due to intra-voxel dephasing. This study investigated the effect of decreasing intra-voxel dephasing by reducing the echo time (TE) on AVA estimates in patients with AS.</p> <p>Method</p> <p>15 patients with moderate or severe AS, were studied with three different TEs (2.8 ms/2.0 ms/1.5 ms), in the main pulmonary artery (MPA), left ventricular outflow tract (LVOT) and 0 cm/1 cm/2.5 cm above the aortic valve (AoV). PC estimates of stroke volume (SV) were compared with CMR left ventricular SV measurements and PC peak velocity, VTI and AVA were compared with Doppler echocardiography. CMR estimates of AVA obtained by direct planimetry from cine acquisitions were also compared with the echoAVA.</p> <p>Results</p> <p>With a TE of 2.8 ms, the mean PC SV was similar to the ventricular SV at the MPA, LVOT and AoV_{0 cm}(by Bland-Altman analysis bias ± 1.96 SD, 1.3 ± 20.2 mL/-6.8 ± 21.9 mL/6.5 ± 50.7 mL respectively), but was significantly lower at AoV₁and AoV_2.5(-29.3 ± 31.2 mL/-21.1 ± 35.7 mL). PC peak velocity and VTI underestimated Doppler echo estimates by approximately 10% with only moderate agreement. Shortening the TE from 2.8 to 1.5 msec improved the agreement between ventricular SV and PC SV at AoV_{0 cm}(6.5 ± 50.7 mL vs 1.5 ± 37.9 mL respectively) but did not satisfactorily improve the PC SV estimate at AoV_{1 cm}and AoV_{2.5 cm}. Agreement of CMR AVA with echoAVA was improved at TE 1.5 ms (0.00 ± 0.39 cm²) versus TE 2.8 (0.11 ± 0.81 cm²). The CMR method which agreed best with echoAVA was direct planimetry (-0.03 cm²± 0.24 cm²).</p> <p>Conclusion</p> <p>Agreement of CMR AVA at the aortic valve level with echo AVA improves with a reduced TE of 1.5 ms. However, flow measurements in the aorta (AoV 1 and 2.5) are underestimated and 95% limits of agreement remain large. Further improvements or novel, more robust techniques are needed in the CMR PC technique in the assessment of AS severity in patients with moderate to severe aortic stenosis.</p

Hyperbranched PEG-based multi-NHS polymer and bioconjugation with BSA

Star-shaped poly(ethylene glycol)-N-hydroxysuccinimide (star- PEG-NHS) has shown great promise in a variety of biomedical applications owing to its non-toxicity, innate non-immunogenic properties and versatile, multifunctional end groups. However, its complex and sophisticated synthetic methods, as well as high costs, have significantly impeded its wide application. Here, we report the design and synthesis of a hyperbranched PEG-based polymer with multiple NHS functional groups (>12). The hyper- branched PEG-based multi-NHS polymer can react easily with a protein (bovine serum albumin, BSA) to form a PEG-protein hydro- gel that displays great potential for biomedical applications

Myocardial T(1) and T(2) mapping at 3 T: reference values, influencing factors and implications

BACKGROUND: Myocardial T1 and T2 mapping using cardiovascular magnetic resonance (CMR) are promising to improve tissue characterization and early disease detection. This study aimed at analyzing the feasibility of T1 and T2 mapping at 3 T and providing reference values. METHODS: Sixty healthy volunteers (30 males/females, each 20 from 20--39 years, 40--59 years, 60--80 years) underwent left-ventricular T1 and T2 mapping in 3 short-axis slices at 3 T. For T2 mapping, 3 single-shot steady-state free precession (SSFP) images with different T2 preparation times were acquired. For T1 mapping, modified Look-Locker inversion recovery technique with 11 single shot SSFP images was used before and after injection of gadolinium contrast. T1 and T2 relaxation times were quantified for each slice and each myocardial segment. RESULTS: Mean T2 and T1 (pre-/post-contrast) times were: 44.1 ms/1157.1 ms/427.3 ms (base), 45.1 ms/1158.7 ms/411.2 ms (middle), 46.9 ms/1180.6 ms/399.7 ms (apex). T2 and pre-contrast T1 increased from base to apex, post-contrast T1 decreased. Relevant inter-subject variability was apparent (scatter factor 1.08/1.05/1.11 for T2/pre-contrast T1/post-contrast T1). T2 and post-contrast T1 were influenced by heart rate (p < 0.0001, p = 0.0020), pre-contrast T1 by age (p < 0.0001). Inter- and intra-observer agreement of T2 (r = 0.95; r = 0.95) and T1 (r = 0.91; r = 0.93) were high. T2 maps: 97.7% of all segments were diagnostic and 2.3% were excluded (susceptibility artifact). T1 maps (pre-/post-contrast): 91.6%/93.9% were diagnostic, 8.4%/6.1% were excluded (predominantly susceptibility artifact 7.7%/3.2%). CONCLUSIONS: Myocardial T2 and T1 reference values for the specific CMR setting are provided. The diagnostic impact of the high inter-subject variability of T2 and T1 relaxation times requires further investigation

Impact of QRS misclassifications on heart-rate-variability parameters (results from the CARLA cohort study)

Background Heart rate variability (HRV), an important marker of autonomic nervous system activity, is usually determined from electrocardiogram (ECG) recordings corrected for extrasystoles and artifacts. Especially in large population-based studies, computer-based algorithms are used to determine RR intervals. The Modular ECG Analysis System MEANS is a widely used tool, especially in large studies. The aim of this study was therefore to evaluate MEANS for its ability to detect non-sinus ECG beats and artifacts and to compare HRV parameters in relation to ECG processing. Additionally, we analyzed how ECG processing affects the statistical association of HRV with cardiovascular disease (CVD) risk factors. Methods 20-min ECGs from 1,674 subjects of the population-based CARLA study were available for HRV analysis. All ECGs were processed with the ECG computer program MEANS. A reference standard was established by experienced clinicians who visually inspected the MEANS-processed ECGs and reclassified beats if necessary. HRV parameters were calculated for 5-minute segments selected from the original 20-minute ECG. The effects of misclassified typified normal beats on i) HRV calculation and ii) the associations of CVD risk factors (sex, age, diabetes, myocardial infarction) with HRV were modeled using linear regression. Results Compared to the reference standard, MEANS correctly classified 99% of all beats. The averaged sensitivity of MEANS across all ECGs to detect non-sinus beats was 76% [95% CI: 74.1;78.5], but for supraventricular extrasystoles detection sensitivity dropped to 38% [95% CI: 36.8;38.5]. Time-domain parameters were less affected by false sinus beats than frequency parameters. Compared to the reference standard, MEANS resulted in a higher SDNN on average (mean absolute difference 1.4ms [95% CI: 1.0;1.7], relative 4.9%). Other HRV parameters were also overestimated as well (between 6.5 and 29%). The effect estimates for the association of CVD risk factors with HRV did not differ between the editing methods.</p

Current T(1) and T(2) mapping techniques applied with simple thresholds cannot discriminate acute from chronic myocadial infarction on an individual patient basis: a pilot study

BACKGROUND: Studying T1- and T2-mapping for discrimination of acute from chronic myocardial infarction (AMI, CMI). METHODS: Eight patients with AMI underwent CMR at 3 T acutely and after >3 months. Imaging techniques included: T2-weighted imaging, late enhancement (LGE), T2-mapping, native and post-contrast T1-mapping. Myocardial T2- and T1-relaxation times were determined for every voxel. Abnormal voxels as defined by having T2- and T1-values beyond a predefined threshold (T2 > 50 ms, native T1 > 1250 ms and post-contrast T1 delete acute infarction; unfortunately this is not possible in your web interface) acute infarction only in half of the subjects. Abnormal T2-values were also present in subjects with CMI, thereby matching the chronically infarcted territory in some. Abnormal native T1 times were present in voxels with AMI in 5/8 subjects, but also remote from the infarcted territory in four. In CMI, abnormal native T1 values corresponded with infarcted voxels, but were also abnormal remote from the infarcted territory. Voxels with abnormal post-contrast T1-relaxation times agreed well with LGE in AMI and CMI. CONCLUSIONS: In this pilot-study, T2- and T1-mapping with simple thresholds did not facilitate the discrimination of AMI and CMI