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Background Atrial fibrillation (AF) is the most common cardiac arrhythmia. It is often treated using catheter ablation, which aims to isolate arrhythmogenic regions by delivering localized energy. Whereas an insufficient energy delivery can lead to AF recurrence, excessive power can cause potentially lethal complications. Knowledge of atrial wall thickness can help select an optimal amount of energy, but clinical imaging does not currently provide atrial wall thickness data for patients. Even ex-vivo studies have only measured the thickness of the atrial wall in discrete locations using CT or post-mortem samples. In this study, we apply black-blood MR imaging to reconstruct both epiand endocardial surfaces of the entire atria and compute wall thickness maps in healthy volunteers. To our knowledge, this is the first study to provide a complete 3D map of the wall thickness of both right and left atria.

Results Figure 1 shows the results of the three dimensional shape analysis. Those receiving a RVPA shunt had highly significant differences (p

Background Aortic Coarctation (AoCo) accounts for 5-8% of the children with CHD. Even after successful early repair, life expectancy is still markedly reduced (80% at 50 years after surgery) compared to normal population due to long term complications (hypertension). Usually, invasive diagnostic catheter investigations are required to evaluate the pressure gradient across the aorta at rest, or unmask such a gradient by use of isoprenaline stress to mimic physical exercise. The application of imagebased computational fluid dynamics (CFD) in patients with AoCo appears promising as an alternative noninvasive diagnostic tool, as it may allow the avoidance of cardiac catheterization to determine pressure gradients. The motivation of this research is to know if a MRI based CFD model can accurately predict the pressure

Background Hypertrophic cardiomyopathy (HCM) is associated with significant associated morbidity and mortality. Increased maximal left ventricular wall thickness (LVWT) has been postulated as major risk factor of sudden death; however, relatives with normal LVWT are also at risk. Genetically driven interstitial collagenesis has been proposed as a possible mechanism of diffuse myocardial fibrosis and increased extracellular volume fractions (ECV) has been demonstrated in genotype positive subjects. We investigated whether native T1 can also separate genotype positive subjects in the absence of increase in LVWT and how does it relate to ECV measurements.

Background Cardiac magnetic resonance (CMR) increasingly adds to clinical conformation of the diagnosis in patients with suspected myocarditis. The proposed Lake Louise Consensus Criteria ("any-two” approach) can separate from chronic forms of myocardial inflammation. However, both global enhancement ratio (GRE) and T2-weighted imaging are underutilized, due to poor reproducibility and high susceptibility to artefacts. T1 and T2 mapping by CMR projects tissue-dependent relaxation times. T2 mapping has been recently proposed as a robust and accurate technique to identify areas of focal myocardial oedema. Our aim was to investigate the value of quantitative T2 values in discrimination between health and disease, and separation between active/acute myocarditis and chronic convalescent stage of the disease. Methods Twenty-four patients with acute presentation of viral myocarditis and twenty-three subjects in clinical convalescence were recruited. Thirty-three healthy subjects were served as controls. All subjects underwent CMR study for routine assessment of myocardial oedema, function and scar by at 3-Tesla scanner. T2 values were acquired in midventricular short-axis slice (mSAX) using GraSE sequence. We examined regional T2 values in patients and controls. T2 values are presented as an average of the six segments per mSAX. Secondly we investigated the differences between visually involved and remote myocardium (involved myocardium = areas by LGE, remote = areas with no LGE) Results Patients with acute myocarditis and chronic myocarditis showed significantly raised T2 values [controls vs. acute vs. chronic myocarditis, T2 myocardium (msec): 48 ± 3 vs. 59 ± 9 vs. 53 ± 5, p < 0.0001). Compared to controls, T2 values in remote myocardium were significantly different for acute myocarditis only (T2, msec: 48 ± 3 vs. 51 ± 5 vs. 49 ± 2, p < 0.01), whereas T2 values in involved myocardium differed between all groups (T2, msec: 48 ± 3 vs. 69 ± 13 vs. 57 ± 8, p < 0.0001]. Using T2 values of complete mSAX or involved were identified as the independent discriminators between active and chronic myocarditis. T2 values were concordant with T2 oedema ratio (T2 involved, r = 0.42, p < 0.0001) and with native T1 (r = 0.55, p < 0.001). Conclusions We demonstrate that quantitative T2 values are increased in patients with myocarditis. We further demonstrate that average mSAX and involved T2 values can discriminate between acute and chronic stage of the disease. Funding

Background Myocardial T1 mapping is emerging as a promising means to non-invasively discriminate between normal and diseased myocardium. Original modified Look-Locker sequence (3’3’5-MOLLI) can induce a long breath-hold and is prone to cardiac and respiratory motion. Several shorter sequences (3’5MOLLI, shMOLLI and SASHA) have been proposed for acquisition of T1 values. We examined native and postcontrast T1 values derived by above sequences within the same subject and investigated their ability to separate between health and disease. We further examined reproducibility of measurements within and between observers.

Background T1 mapping by cardiovascular magnetic resonance (CMR) provides tissue-dependent relaxation times in line with the underlying myocardial composition. In this study, we examined the value of native T1 in differentiation between acute viral myocarditis and chronic stages of healing. Methods Fifty-three patients with a clinical diagnosis of acute viral myocarditis were compared to fifty-six subjects in clinical convalescence. All subjects underwent assessment of myocardial oedema, function and scar by CMR at 1.5 and 3-Tesla. T1 values were measured in midventricular short-axis slice prior to and after administration of 0.2 mmol/kg of gadobutrol. Results Compared to controls (n = 40), native T1 values were increased in both acute and chronic myocarditis at both field strengths (controls vs. acute vs. chronic myocarditis; 1.5T: native T1 (msec): 940 ± 17 vs. 1070 ± 34 vs. 998 ± 28, p < 0.001; 3T: 1045 ± 18 vs. 1182 ± 66 vs. 1094 ± 15, p < 0.001). Native T1 values were significantly higher in acute vs. chronic myocardium (p < 0.001). Native T1 was identified as the independent discriminator between health and disease, as well as acute and chronic myocarditis (Figure 1). Native T1 showed gradual reduction of values between acute and chronic stage of myocardial inflammation.

Background Increased inflammation has been linked to myocardial dysfunction and heart failure. We investigated whether T1 mapping by cardiovascular magnetic resonance (CMR) in patients with systemic lupus erythematosus (SLE) can detect subclinical cardiac involvement.

Background Classical modified Look-Locker sequence (MOLLI) can induce a long breath-hold and is prone to cardiac and respiratory motion. Several shorter sequences based on inversion (3’5MOLLI, shMOLLI) and saturation recovery (SASHA) of longitudinal relaxation have been proposed for derivation of T1 values or calculation of extracellular volume fraction or lambdas. Despite the validation in T1 gel phantoms, it has not been determined whether these novel sequences provide equivalent information on T1 when performed within the same individual. Methods Twenty-three subjects underwent T1 mapping in a midventricular equatorial short axis slice using above sequences on 3T clinical scanner prior and after gadolinium contrast (0.2 mmol/kg) administration. The images were analyzed using PRIDE tool with in-built automated motion correction. ROIs were drawn conservatively within the septal and lateral myocardium and the blood pool. Comparison of the native T1 values and lambdas were performed and expressed as percentage of mean difference from the values obtained with goldstandard MOLLI sequence.

Background T1 mapping enables true quantitative assessment of myocardial tissue, separating scars and healthy myocardium. The modified Look-Locker inversion recovery (MOLLI) sequence acquires eleven images over the duration of a minimum of fifteen heart beats to obtain the final T1 map, which is susceptible to undesired respiratory motion due to a relatively long breath-hold. We aimed to implement a motion correction method using a hierarchical local affine registration of MOLLI images and tested if it improved image quality and thus produced more accurate post contrast myocardial tissue T1 estimation.

Methods A standard ultrafast gradient echo perfusion sequence (st-GrE) was compared with an advanced kt-accelerated steady state free precession sequence (kt-SSFP) at 1.5T in a hardware perfusion phantom, healthy volunteers (n=16) and patients (n=31) with known or suspected coronary artery disease. Volunteers had both sequences at rest in alternating order. Patients underwent stress imaging with either st-GrE (15) or kt-SSFP (16) prior to X-ray coronary angiography. The phantom was used to generate signal intensity curves and noise maps for SNR and CNR analysis. Human images were analysed by a blinded observer using a nominal scale for quality (0 non-diagnostic, 1 poor, 2 moderate, 3 good, 4 excellent) and respiratory artefacts (0 non-diagnostic, 1 severe, 2 moderate, 3 minor, 4 nil) and also for the presence of CAD in patients. Other analyses included the extent (% affected segments), transmurality (1: 1-25%, 2: 26-50%, 3: 5175%, 4 76-100%) and duration (frames) of dark rim artefacts (DRA). Segmental SNR and CNR were also quantified using the mid ventricular slice in volunteers.

Background Delayed-enhancement (DE) MRI is an effective technique for imaging left atrial (LA) ablation lesions following radio-frequency ablation for atrial fibrillation (AF). Existing techniques for segmentation/visualization of lesions require manual interaction of an expert user making them prone to high observer variability. Oakes et al.[1] applied thresholding on the intensity histogram of the manually-outlined atrial wall. Peters et al.[2] used maximum intensity projections (MIPs) to generate volume lesion visualizations for expert-user interpretation. Knowles et al.[3] employed MIP followed by userinteractive thresholding for lesion surface visualization.

Background ICD implantation is known to improve prognosis in patients with ischemic cardiomyopathy (ICM). Determining which patients are at high risk of ventricular arrhythmias and sudden death remains difficult. The presence and extent of grey zone detected by CMR has been linked to ventricular arrhythmias and may be useful in determining which patients should have an ICD. Several processing methods to define the area of grey zone based on traditional late enhancement sequences (LGE) have been developed. Recently, a novel delayed enhancement sequence (MCDE) combined with an automated segmentation method was introduced to more accurately assess the peri-infarct area. 1,2 One limitation of this technique is the presence of cardiac motion in the image making the analysis cumbersome as the images from the same point in the cardiac cycle need to be filtered out of the dataset during postprocessing. An alternative option for the quantitative T1 measurement of the grey zone is the modified look-locker (MOLLI), which is not affected by cardiac motion. In the current study, the MCDE and MOLLI sequences were compared for the evaluation of the grey zone.

A single-phase 3d steady-state-free precession whole heart approach with respiratory navigator gating and ECG triggering (3d SSFP) is now frequently used for diagnostic imaging in children with congenital heart disease (CHD). However, certain cardiac structures may be better assessed during the systolic and others in the diastolic rest period. Therefore, a previously described dual phase 3d-SSFP whole heart sequence may offer clinical benefit in these patients. (Uribe et al 2008)

Methods Our MR-compatible phantom resembles the anatomy of the heart and of the thoracic vessels of a 60 kg subject. Water flow (2-4 l/min) is driven into the system by a pump located outside the MR room. Gadolinium injections (Gadovist, gadobutrol, Bayer Schering, Germany) are performed in the vena cava by a power-injector (Medrad Solaris, Germany). Progressive dilution of the Gadolinium bolus across the chambers generates the AIF. A fraction of the cardiac output perfuses two myocardial compartments (made by arrays of parallel tubes) where perfusion can be controlled precisely and independently. Outside the MR room, a control unit allows for precise measurement and control of cardiac output and myocardial perfusion. The phantom was tested in a 3T-scanner (Philips Achieva, Netherlands). Acquisition of the perfusion sequence was repeated multiple times with a k-t SENSE sequence (flip-angle=20°; TR2.2 ms; TE1.1 ms; k-t factor 5, 11 training profiles) using similar flow conditions to demonstrate the reproducibility of the measurements. Different flow conditions were used to assess the response of the system to different myocardial perfusion rates. Quantification was performed by Fermi deconvolution.

Percutaneous cardiac interventions are currently performed under X-ray guidance. MR-guided cardiac interventions have been previously described but mainly in animals. Their translation into humans has been limited by the lack of MR-compatible and safe equipment, such as MR guidewires with mechanical characteristics similar to standard guidewires.

Background Perfusion imaging visualizes early changes within the ischaemic cascade and has been shown to accurately detect significant coronary artery stenoses. First pass myocardial perfusion CMR yields high spatial resolution and permits quantification of myocardial blood flow. However, perfusion-CMR has only been validated in a small number of previous studies and using relatively early perfusion methods. An isolated blood-perfused MR compatible porcine heart model which can be imaged by identical equipment used for humans has been recently proposed. The model permits full control of regional myocardial blood flow, thus providing a valuable tool for the validation of quantitative perfusion assessment.

It is known that 30-40% of heart failure patients that undergo cardiac resynchronization therapy (CRT) do not derive significant clinical benefit. Using cine imaging a measure of volume change over the cardiac cycle can be derived called the Systolic Dyssynchrony Index (SDI). This has the potential to improve patient selection pre CRT.