Marcel Prothmann

Acoustic cardiac triggering: a practical solution for synchronization and gating of cardiovascular magnetic resonance at 7 Tesla.

BackgroundTo demonstrate the applicability of acoustic cardiac triggering (ACT) for imaging of the heart at ultrahigh magnetic fields (7.0 T) by comparing phonocardiogram, conventional vector electrocardiogram (ECG) and traditional pulse oximetry (POX) triggered 2D CINE acquisitions together with (i) a qualitative image quality analysis, (ii) an assessment of the left ventricular function parameter and (iii) an examination of trigger reliability and trigger detection variance derived from the signal waveforms.ResultsECG was susceptible to severe distortions at 7.0 T. POX and ACT provided waveforms free of interferences from electromagnetic fields or from magneto-hydrodynamic effects. Frequent R-wave mis-registration occurred in ECG-triggered acquisitions with a failure rate of up to 30% resulting in cardiac motion induced artifacts. ACT and POX triggering produced images free of cardiac motion artefacts. ECG showed a severe jitter in the R-wave detection. POX also showed a trigger jitter of approximately Δt = 72 ms which is equivalent to two cardiac phases. ACT showed a jitter of approximately Δt = 5 ms only. ECG waveforms revealed a standard deviation for the cardiac trigger offset larger than that observed for ACT or POX waveforms.Image quality assessment showed that ACT substantially improved image quality as compared to ECG (image quality score at end-diastole: ECG = 1.7 ± 0.5, ACT = 2.4 ± 0.5, p = 0.04) while the comparison between ECG vs. POX gated acquisitions showed no significant differences in image quality (image quality score: ECG = 1.7 ± 0.5, POX = 2.0 ± 0.5, p = 0.34).ConclusionsThe applicability of acoustic triggering for cardiac CINE imaging at 7.0 T was demonstrated. ACTs trigger reliability and fidelity are superior to that of ECG and POX. ACT promises to be beneficial for cardiovascular magnetic resonance at ultra-high field strengths including 7.0 T.

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

BackgroundThe 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.MethodsHealthy 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.ResultsIn 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 < 0.0001 for both). Anteroseptal and apical segments had higher T2 than inferior and basal segments (SAX: 59 ± 6 vs. 48 ± 5 ms for FLASH and 59 ± 7 vs. 52 ± 4 ms for SSFP; p < 0.0001 for both). 14 volunteers had segments with T2 ≥ 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.ConclusionsMyocardial 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.

Impact of surgical correction of pectus excavatum on cardiac function: insights on the right ventricle. A cardiovascular magnetic resonance study †

OBJECTIVES Pectus excavatum (PE) is often regarded as a cosmetic disease, while its effect on cardiac function is under debate. Data regarding cardiac function before and after surgical correction of PE are limited. We aimed to assess the impact of surgical correction of PE on cardiac function by cardiovascular magnetic resonance (CMR). METHODS CMR at 1.5 T was performed in 38 patients (mean age 21 ± 8.3; 31 men) before and after surgical correction to evaluate thoracic morphology, indices and its relation to three-dimensional left and right ventricular cardiac function. RESULTS Surgery was successful in all patients as shown by the Haller Index ratio of maximum transverse diameter of the chest wall and minimum sternovertebral distance [pre: 9.64 (95% CI 8.18-11.11) vs post: 3.0 (2.84-3.16), P < 0.0001]. Right ventricular ejection fraction (RVEF) was reduced before surgery and improved significantly at the 1-year follow-up [pre: 45.7% (43.9-47.4%) vs 48.3% (46.9-49.5%), P = 0.0004]. Left ventricular ejection fraction was normal before surgery, but showed a further improvement after 1 year [pre: 61.0% (59.3-62.7%) vs 62.7% (61.3-64.2%), P = 0.0165]. Cardiac compression and the asymmetry index changed directly after surgery and were stable at the 1-year follow-up [3.93 (3.53-4.33) vs 2.08 (1.98-2.19) and 2.36 (2.12-2.59) vs 1.38 (1.33-1.44), respectively; P < 0.0001 for both]. None of the obtained thoracic indices were predictors of the improvement of cardiac function. A reduced preoperative RVEF was predictive of RVEF improvement. CONCLUSIONS PE is associated with reduced RVEF, which improves after surgical correction. CMR has the capability of offering additional information prior to surgical correction.

A T1 and ECV phantom for global T1 mapping quality assurance: The T1 mapping and ECV standardisation in CMR (T1MES) program

Background Myocardial T1 and extracellular volume (ECV) estimates have applications in a range of myocardial diseases. Factors responsible for systematic inaccuracies in T1 mapping are beginning to be known but little is known about its delivery at ‘health-care system’ scale and there is no global quality assurance (QA) system. Agarose phantoms are common in MRI and nickel ions preferred for lower temperature sensitivity. This program aims to 1 Create a partnership to design 1.5/3T phantoms for any manufacturer/sequence reflecting myocardial/blood T1 pre/post-contrast 2 Test and mass produce phantoms to regulatory standards 3 Distribute globally 4 Analyse serial scans to understand T1 mapping at scale 5 Publish recipes 6 Explore delivery of a ‘T1/ECV Standard’ via local calibration We report results of steps 1-3.

High Spatial Resolution Cardiovascular Magnetic Resonance at 7.0 Tesla in Patients with Hypertrophic Cardiomyopathy – First Experiences: Lesson Learned from 7.0 Tesla

Background Cardiovascular Magnetic Resonance (CMR) provides valuable information in patients with hypertrophic cardiomyopathy (HCM) based on myocardial tissue differentiation and the detection of small morphological details. CMR at 7.0T improves spatial resolution versus today’s clinical protocols. This capability is as yet untapped in HCM patients. We aimed to examine the feasibility of CMR at 7.0T in HCM patients and to demonstrate its capability for the visualization of subtle morphological details. Methods We screened 131 patients with HCM. 13 patients (9 males, 56 ±31 years) and 13 healthy age- and gender-matched subjects (9 males, 55 ±31years) underwent CMR at 7.0T and 3.0T (Siemens, Erlangen, Germany). For the assessment of cardiac function and morphology, 2D CINE imaging was performed (voxel size at 7.0T: (1.4x1.4x2.5) mm3 and (1.4x1.4x4.0) mm3; at 3.0T: (1.8x1.8x6.0) mm3). Late gadolinium enhancement (LGE) was performed at 3.0T for detection of fibrosis. Results All scans were successful and evaluable. At 3.0T, quantification of the left ventricle (LV) showed similar results in short axis view vs. the biplane approach (LVEDV, LVESV, LVMASS, LVEF) (p = 0.286; p = 0.534; p = 0.155; p = 0.131). The LV-parameters obtained at 7.0T where in accordance with the 3.0T data (pLVEDV = 0.110; pLVESV = 0.091; pLVMASS = 0.131; pLVEF = 0.182). LGE was detectable in 12/13 (92%) of the HCM patients. High spatial resolution CINE imaging at 7.0T revealed hyperintense regions, identifying myocardial crypts in 7/13 (54%) of the HCM patients. All crypts were located in the LGE-positive regions. The crypts were not detectable at 3.0T using a clinical protocol. Conclusions CMR at 7.0T is feasible in patients with HCM. High spatial resolution gradient echo 2D CINE imaging at 7.0T allowed the detection of subtle morphological details in regions of extended hypertrophy and LGE.

Magnetic Resonance Imaging Applications on Infiltrative Cardiomyopathies.

Infiltrative cardiomyopathies are a heterogenous group of diseases that typically lead to restrictive cardiac dysfunction. Due to similar phenotypes, accurate diagnosis is challenging without invasive endomyocardial biopsy which has historically been considered mandatory. Cardiac magnetic resonance (CMR) has been well established in the diagnostic workup of patients with suspected cardiomyopathies due to its unique capability for tissue differentiation and its unsurpassed accuracy in defining cardiac morphology and function. The increasing variety of CMR techniques has generated both excitement and uncertainty with regard to their potential clinical use and its role vis-à-vis conventional noninvasive imaging techniques. The purpose of this review is to give an overview of established and emerging CMR techniques and typical image characteristics of the most commonly encountered infiltrative cardiomyopathies.

Differentiation of acute and chronic myocardial infarction using T2-weighted imaging, late enhancement and T1 and T2 mapping - a pilot study at 3T

Background Qualitative assessment of myocardial T2-weighted and late enhancement (LGE) images has been demonstrated to differentiate acute from chronic myocardial infarction (AMI, CMI). Parametric mapping could help to overcome challenges in image quality and could contribute to making contrast media application obsolete. The aim of this pilot study was to analyze, whether T2and T1maps are useful to discriminate AMI from CMI.

Equivalence of conventional and fast late gadolinium enhancement (LGE) techniques for quantitative evaluation of fibrosis in ischemic and non-ischemic cardiac disease - Save the Time!

Methods Patients with myocardial infarction (n = 45), myocarditis (n = 25) or hypertrophic cardiomyopathy (HCM) (n = 15) were prospectively enrolled. After administration of gadolinium contrast agent, LGE images were acquired ECG-gated in short axis slices (slice thickness 7 mm, no gap) using 4 different LGE sequences: (1) conventional segmented 2D phase-sensitive inversion recovery in single-slice/single-breath-hold technique (2D-PSIR; gold standard; TR 744 ms, TE 5,17 ms, voxel size 1.4 × 1.4 × 7.0 mm), (2) single-breath-hold 3D-IR sequence (3D-IR bh; TR 924 ms, TE 1.06 ms, voxel size 1.9 × 1.9 × 7.0 mm), (3) single breath-hold 3D-SSFP sequence (3DSSFP; TE 700 ms, TE 1.05 ms, voxel size 1.9 × 1.9 × 7.0 mm) and (4) non-breath-hold technique (3D-IR nbh). (Figure 1) For all techniques, inversion time was individually adjusted to null the remote myocardium. Myocardial fibrosis was quantitatively assessed using a semiautomated threshold method; positive LGE was defined as signal intensity 6 standard deviations (SD) above signal intensity of remote myocardium for myocardial infarction and 3 SD for myocarditis / HCM. Detection rates were determined as number of matching myocardial AHA segments with detected LGE in gold standard and each fast technique.

Abnormal regional myocardial morphology in patients with left ventricular pressure overload and preserved ejection fraction detected by multiparametric MR tissue mapping

Charité Medical Faculty and HELIOS clinics, Working group Cardiovascular MRI, Berlin, Germany Full list of author information is available at the end of the article Figure 1 Mean ± SD of T2and T1-relaxation times and partition coefficient per segment. Segments that differed significantly from healthy controls are marked “*” and highlighted in orange. von Knobelsdorff-Brenkenhoff et al. Journal of Cardiovascular Magnetic Resonance 2016, 18(Suppl 1):P336 http://www.jcmr-online.com/content/18/S1/P336

Combined parametric mapping allows discrimination of disease activity in myocarditis

Background Noninvasive detection of myocarditis is a unique feature of Cardiovascular Magnetic Resonance (CMR), but conventional CMR-imaging suffers from different challenges including imaging quality. It has already been shown, that T1 mapping has the potential to identify acute myocarditis [1,2]. We aim to differentiate the course of disease and to identify the acute stage by combining mapping techniques.