Three-dimensional assessment of image distortion induced by active cardiac implants in 3.0T CMR

CMR at 3.0T in the presence of active cardiac implants remains a challenge due to susceptibility artifacts. Beyond a signal void that cancels image information, magnetic field inhomogeneities may cause distorted appearances of anatomical structures. Understanding influencing factors and the extent of distortion are a first step towards optimizing the image quality of CMR with active implants at 3.0T. All measurements were obtained at a clinical 3.0T scanner. An in-house designed phantom with a 3D cartesian grid of water filled spheres was used to analyze the distortion caused by four representative active cardiac devices (cardiac loop recorder, pacemaker, 2 ICDs). For imaging a gradient echo (3D-TFE) sequence and a turbo spin echo (2D-TSE) sequence were used. The work defines metrics to quantify the different features of distortion such as changes in size, location and signal intensity. It introduces a specialized segmentation technique based on a reaction-diffusion-equation. The distortion features are dependent on the amount of magnetic material in the active implants and showed a significant increase when measured with the 3D TFE compared to the 2D TSE. This work presents a quantitative approach for the evaluation of image distortion at 3.0T caused by active cardiac implants and serves as foundation for both further optimization of sequences and devices but also for planning of imaging procedures.

Cardiac function in a large animal model of myocardial infarction at 7 T: deep learning based automatic segmentation increases reproducibility

Cardiac magnetic resonance (CMR) imaging allows precise non-invasive quantification of cardiac function. It requires reliable image segmentation for myocardial tissue. Clinically used software usually offers automatic approaches for this step. These are, however, designed for segmentation of human images obtained at clinical field strengths. They reach their limits when applied to preclinical data and ultrahigh field strength (such as CMR of pigs at 7 T). In our study, eleven animals (seven with myocardial infarction) underwent four CMR scans each. Short-axis cine stacks were acquired and used for functional cardiac analysis. End-systolic and end-diastolic images were labelled manually by two observers and inter- and intra-observer variability were assessed. Aiming to make the functional analysis faster and more reproducible, an established deep learning (DL) model for myocardial segmentation in humans was re-trained using our preclinical 7 T data (n = 772 images and labels). We then tested the model on n = 288 images. Excellent agreement in parameters of cardiac function was found between manual and DL segmentation: For ejection fraction (EF) we achieved a Pearson's r of 0.95, an Intraclass correlation coefficient (ICC) of 0.97, and a Coefficient of variability (CoV) of 6.6%. Dice scores were 0.88 for the left ventricle and 0.84 for the myocardium.

Accuracy of VO2 estimation according to the widely used Krakau formula for the prediction of cardiac output

BACKGROUND

Invasive cardiac output (CO) is measured with the thermodilution (TD) or the indirect Fick method (iFM) in right heart catheterization (RHC). The iFM estimates CO using approximation formulas for oxygen consumption ([Formula: see text]O2), but there are significant discrepancies (> 20%) between both methods. Although regularly applied, the formula proposed by Krakau has not been validated. We compared the CO discrepancies between the Krakau formula with the reference (TD) and three established formulas and investigated whether alterations assessed in cardiac magnetic resonance imaging (CMR) determined the extent of the deviations.

METHODS

This retrospective study included 188 patients aged 63 ± 14 years (30% women) receiving both CMR and RHC. The CO was measured with TD or with the iFM using the formulas by Krakau, LaFarge, Dehmer, and Bergstra for [Formula: see text]O2 estimation (iFM-K/-L/-D/-B). Percentage errors were calculated as twice the standard deviation of the difference between two CO methods divided by their means; a cut-off of < 30% was regarded as acceptable. The iFM and TD-derived CO ratio was built, and deviations > 20% were counted. Logistic regression analyses were performed to identify determinants of a deviation of > 20%.

RESULTS

The TD-derived CO (5.5 ± 1.7 L/min) was significantly different from all iFM (K: 4.8 ± 1.6, L: 4.3 ± 1.6; D: 4.8 ± 1.5 L/min; B: 5.4 ± 1.8 L/min all p < 0.05). The iFM-K-CO differed from all methods (p < 0.001) except iFM‑D (p = 0.19). Percentage errors between TD-CO and iFM-K/-L/-D/-B were all beyond the acceptance limit (44/45/44/43%), while percentage errors between iFM‑K and other iFM were all < 16%. None of the parameters measured in CMR was predictive of a discrepancy of > 20% between both methods.

CONCLUSION

The Krakau formula was comparable to other iFM in estimating CO levels, but none showed satisfactory agreement with the TD method. Improved derivation cohorts for [Formula: see text]O2 estimation are needed that better reflect today's patients undergoing RHC.

Complementary analysis of specific absorption rate safety for an 8Tx/16Rx array with central symmetry of elements for magnetic resonance imaging of the human heart and abdominopelvic organs at 7 T

A complementary safety assessment of the specific absorption rate (SAR) of the electromagnetic energy was performed in a prototype 8Tx/16Rx RF array for cardiac magnetic resonance imaging (MRI) at 7 T. The study aimed to address two critical aspects of 7-T SAR safety not always explicitly examined by coil vendors: (i) the influence of an RF-array position on a peak SAR value, and (ii) the risk of exceeding the permitted maximal SAR in the tissue surrounding conductive passive implants. The full-wave 3D electromagnetic simulations for the thorax with shifted array position and the whole-body volume in the presence of a dental retainer, an intrauterine contraceptive device (IUD), and a hip joint implant, were performed for two human voxel models. The effect of the array displacement on the SAR was simulated for seven array locations on the thorax shifted from the central position in different directions on 50 mm. The peak SAR values for both models were analyzed for the three phase-only transmit vectors optimized for B1 + homogeneity and transmit efficiency. Peak SAR values due to the shifts of the array position increase up to ≈50%. The worst-case peak SAR value for a dental retainer was found to be in the range of 10% of the maximal SAR in the tissue within the array's borders. For the IUD and artificial hip joint implants the effect was found to be negligible (peak SAR < 1% of the SAR within array borders). In addition to simulations for cardiac MRI, we performed a preliminary B1 + shimming and SAR-safety analysis for the same RF-array at various positions lower on the body trunk to assess a potential application in imaging abdominopelvic organs (prostate, kidney, and liver). The most promising target for an ad hoc alternative application of the array was found to be the prostate.

Diagnosing post-capillary hypertension in patients with left heart disease: impact of new guidelines

BACKGROUND

In 2022, the definition of pulmonary hypertension (PH) in the presence of left heart disease was updated according to the new joint guidelines of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS). The impact of the new ESC/ERS definition on the prevalence of post-capillary PH (pc-PH) and its subgroups of isolated post-capillary (Ipc-PH) and combined pre- and post-capillary PH (Cpc-PH) in patients with left heart disease is unclear.

METHODS

We retrospectively identified N = 242 patients with left heart disease with available data on right heart catheterisation (RHC) and cardiac magnetic resonance imaging (CMR). The proportion of pc-PH and its subgroups was calculated according to the old and new ESC/ERS PH definition. As the old definition did not allow the exact allocation of all patients with pc-PH into a respective subgroup, unclassifiable patients (Upc-PH) were regarded separately.

RESULTS

Seventy-six out of 242 patients had pc-PH according to the new ESC/ERS definitions, with 72 of these patients also meeting the criteria of the old definition. Using the old definition, 50 patients were diagnosed with Ipc-PH, 4 with Cpc-PH, and 18 with Upc-PH. Applying the new definition, Ipc-PH was diagnosed in 35 patients (4 newly), and Cpc-PH in 41 patients. No CMR parameter allowed differentiating between Ipc-PH and Cpc-PH, regardless of which guideline version was used.

CONCLUSION

Applying the new ESC/ERS 2022 guideline definitions mildly increased the proportion of patients diagnosed with pc-PH (+ 5.5%) but markedly increased Cpc-PH diagnoses. This effect was driven by the allocation of patients with formerly unclassifiable forms of post-capillary PH to the Cpc-PH subgroup and a significant shift of patients from the Ipc-PH to the Cpc-PH subgroup. Distribution of post-capillary pulmonary hypertension (pc-PH) subgroups according to the European Society of Cardiology/European Respiratory Society (ESC/ERS) PH guidelines from 2015 and 2022 in N = 242 patients with left heart disease.

Ultra-high field cardiac MRI in large animals and humans for translational cardiovascular research

A key step in translational cardiovascular research is the use of large animal models to better understand normal and abnormal physiology, to test drugs or interventions, or to perform studies which would be considered unethical in human subjects. Ultrahigh field magnetic resonance imaging (UHF-MRI) at 7 T field strength is becoming increasingly available for imaging of the heart and, when compared to clinically established field strengths, promises better image quality and image information content, more precise functional analysis, potentially new image contrasts, and as all in-vivo imaging techniques, a reduction of the number of animals per study because of the possibility to scan every animal repeatedly. We present here a solution to the dual use problem of whole-body UHF-MRI systems, which are typically installed in clinical environments, to both UHF-MRI in large animals and humans. Moreover, we provide evidence that in such a research infrastructure UHF-MRI, and ideally combined with a standard small-bore UHF-MRI system, can contribute to a variety of spatial scales in translational cardiovascular research: from cardiac organoids, Zebra fish and rodent hearts to large animal models such as pigs and humans. We present pilot data from serial CINE, late gadolinium enhancement, and susceptibility weighted UHF-MRI in a myocardial infarction model over eight weeks. In 14 pigs which were delivered from a breeding facility in a national SARS-CoV-2 hotspot, we found no infection in the incoming pigs. Human scanning using CINE and phase contrast flow measurements provided good image quality of the left and right ventricle. Agreement of functional analysis between CINE and phase contrast MRI was excellent. MRI in arrested hearts or excised vascular tissue for MRI-based histologic imaging, structural imaging of myofiber and vascular smooth muscle cell architecture using high-resolution diffusion tensor imaging, and UHF-MRI for monitoring free radicals as a surrogate for MRI of reactive oxygen species in studies of oxidative stress are demonstrated. We conclude that UHF-MRI has the potential to become an important precision imaging modality in translational cardiovascular research.

CMR detects extensive intracavitary thrombi as solitary clinical presentation of Antiphospholipid Syndrome: A case report

Intracavitary thrombi are an important differential diagnosis of cardiac masses. Cardiac magnetic resonance imaging (CMR) allows their non‐invasive characterization. This case highlights extensive cardiac thrombi detected by CMR as solitary presentation of antiphospholipid syndrome.

Signal voids of active cardiac implants at 3.0 T CMR

Recent technical advancements allow cardiac MRI (CMR) examinations in the presence of so-called MRI conditional active cardiac implants at 3.0 T. However, the artifact burden caused by susceptibility effects remain an obstacle. All measurements were obtained at a clinical 3.0 T scanner using an in-house designed cubic phantom and optimized sequences for artifact evaluation (3D gradient echo sequence, multi-slice 2D turbo spin echo sequence). Reference sequences according to the American Society for Testing and Materials (ASTM) were additionally applied. Four representative active cardiac devices and a generic setup were analyzed regarding volume and shape of the signal void. For analysis, a threshold operation was applied to the grey value profile of each data set. The presented approach allows the evaluation of the signal void and shape even for larger implants such as ICDs. The void shape is influenced by the orientation of the B0-field and by the chosen sequence type. The distribution of ferromagnetic material within the implants also matters. The void volume depends both on the device itself, and on the sequence type. Disturbances in the B0 and B1 fields exceed the visual signal void. This work presents a reproducible and highly defined approach to characterize both signal void artifacts at 3.0 T and their influencing factors.

Saturation recovery-prepared magnetic resonance angiography for assessment of left atrial and esophageal anatomy

OBJECTIVES

Magnetic resonance angiography (MRA) has been established as an important imaging method in cardiac ablation procedures. In pulmonary vein (PV) isolation procedures, MRA has the potential to minimize the risk of severe complications, such as atrio-esophageal fistula, by providing detailed information on esophageal position relatively to cardiac structures. However, traditional non-gated, first-pass (FP) MRA approaches have several limitations, such as long breath-holds, non-uniform signal intensity throughout the left atrium (LA), and poor esophageal visualization. The aim of this observational study was to validate a respiratory-navigated, ECG-gated (EC), saturation recovery-prepared MRA technique for simultaneous imaging of LA, LA appendage, PVs, esophagus, and adjacent anatomical structures.

METHODS

Before PVI, 106 consecutive patients with a history of AF underwent either conventional FP-MRA (n = 53 patients) or our new EC-MRA (n = 53 patients). Five quality scores (QS) of LA and esophagus visibility were assessed by two experienced readers. The non-parametric Mann-Whitney U-test was used to compare QS between FP-MRA and EC-MRA groups, and linear regression was applied to assess clinical contributors to image quality.

RESULTS

EC-MRA demonstrated significantly better image quality than FP-MRA in every quality category. Esophageal visibility using the new MRA technique was markedly better than with the conventional FP-MRA technique (median 3.5 [IQR 1] vs median 1.0, p < 0.001). In contrast to FP-MRA, overall image quality of EC-MRA was not influenced by heart rate.

CONCLUSION

Our ECG-gated, respiratory-navigated, saturation recovery-prepared MRA technique provides significantly better image quality and esophageal visibility than the established non-gated, breath-holding FP-MRA. Image quality of EC-MRA technique has the additional advantage of being unaffected by heart rate.

ADVANCES IN KNOWLEDGE

Detailed information of cardiac anatomy has the potential to minimize the risk of severe complications and improve success rates in invasive electrophysiological studies. Our novel ECG-gated, respiratory-navigated, saturation recovery-prepared MRA technique provides significantly better image quality of LA and esophageal structures than the traditional first-pass algorithm. This new MRA technique is robust to arrhythmia (tachycardic, irregular heart rates) frequently observed in AF patients.

Deep learning-based cardiac cine segmentation: Transfer learning application to 7T ultrahigh-field MRI

PURPOSE

Artificial neural networks show promising performance in automatic segmentation of cardiac MRI. However, training requires large amounts of annotated data and generalization to different vendors, field strengths, sequence parameters, and pathologies is limited. Transfer learning addresses this challenge, but specific recommendations regarding type and amount of data required is lacking. In this study, we assess data requirements for transfer learning to experimental cardiac MRI at 7T where the segmentation task can be challenging. In addition, we provide guidelines, tools, and annotated data to enable transfer learning approaches by other researchers and clinicians.

METHODS

A publicly available segmentation model was used to annotate a publicly available data set. This labeled data set was subsequently used to train a neural network for segmentation of left ventricle and myocardium in cardiac cine MRI. The network is used as starting point for transfer learning to 7T cine data of healthy volunteers (n = 22; 7873 images) by updating the pre-trained weights. Structured and random data subsets of different sizes were used to systematically assess data requirements for successful transfer learning.

RESULTS

Inconsistencies in the publically available data set were corrected, labels created, and a neural network trained. On 7T cardiac cine images the model pre-trained on public imaging data, acquired at 1.5T and 3T, achieved DICE_LV = 0.835 and DICE_MY = 0.670. Transfer learning using 7T cine data and ImageNet weight initialization improved model performance to DICE_LV = 0.900 and DICE_MY = 0.791. Using only end-systolic and end-diastolic images reduced training data by 90%, with no negative impact on segmentation performance (DICE_LV = 0.908, DICE_MY = 0.805).

CONCLUSIONS

This work demonstrates and quantifies the benefits of transfer learning for cardiac cine image segmentation. We provide practical guidelines for researchers planning transfer learning projects in cardiac MRI and make data, models, and code publicly available.

First-line daratumumab shows high efficacy and tolerability even in advanced AL amyloidosis: the real-world experience

Background

Daratumumab was the first monoclonal CD38 antibody with single-agent activity approved for the treatment of multiple myeloma. Moreover, daratumumab demonstrated high response rates in relapsed immunoglobulin light-chain (AL) amyloidosis.

Patients and methods

In our single-center retrospective real-life case series, we analyzed the efficacy and safety of daratumumab as first-line treatment. Daratumumab was administered with low-dose dexamethasone alone or in combination with other multiple myeloma therapeutics

Results

Fourteen patients were eligible, including nine patients with cardiac stage IIIa or IIIb. Overall hematologic response rate was 100%, with 64.3% achieving complete response after a median of 16 cycles of treatment. Median time to hematologic response was 1.4 months. Organ response rates were 45.5% after a median of 4.0 months and 66.7% after a median of 10.0 months, for heart and kidney involvement, respectively. After a median follow-up of 20.5 months, two patients underwent successful autologous stem cell transplantation (ASCT), while another three patients were in preparation for ASCT. Three patients remained on daratumumab at the last follow-up. There were no unexpected toxicities and no grade III or IV adverse events, although more than half of our patients were in stage IIIa or IIIb.

Conclusion

Daratumumab proved to be highly effective in newly diagnosed AL amyloidosis with excellent hematologic and organ response rates, a remarkable safety profile, and good tolerability even in patients with advanced stage of disease.

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Daratumumab yields high hematologic response rates in untreated AL amyloidosis.

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Treatment is well tolerated even in advanced disease stages.

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No unexpected toxicity was observed.

Rationale and design of the cardiovascular status in patients with endogenous cortisol excess study (CV-CORT-EX): a prospective non-interventional follow-up study

BACKGROUND

Endogenous Cushing's syndrome (CS) results in increased cardiovascular (CV) morbidity and mortality. So far, most studies focussed on distinct disease entities rather than the integrity of the CV system. We here describe the design of the Cardiovascular Status in Endogenous Cortisol Excess Study (CV-CORT-EX), a study aiming to comprehensively investigate the health status of patients with endogenous CS (with a particular focus on CV phenotypes, biochemical aspects, quality of life, and psychosocial status).

METHOD

A prospective non-interventional cohort study performed at a German tertiary referral centre. At the time of enrolment, patients will be categorised as: (1) newly diagnosed overt CS, (2) recurrent overt CS, (3) CS in remission, (4) presence of mild autonomous cortisol excess (MACE). The target cohorts will be n = 40 (groups 1 + 2), n = 80 (group 3), and n = 20 (group 4). Patients with overt CS at the time of enrolment will be followed for 12 months after remission (with re-evaluations after 6 and 12 months). At each visit, patients will undergo transthoracic echocardiography, cardiac magnetic resonance imaging, 24-h electrocardiogram, 24-h blood pressure measurement, and indirect evaluation of endothelial function. Furthermore, a standardised clinical investigation, an extensive biochemical workup, and a detailed assessment of quality of life and psychosocial status will be applied. Study results (e.g. cardiac morphology and function according to transthoracic echocardiography and cardiac magnetic resonance imaging; e.g. prevalence of CV risk factors) from patients with CS will be compared with matched controls without CS derived from two German population-based studies.

DISCUSSION

CV-CORT-EX is designed to provide a comprehensive overview of the health status of patients with endogenous CS, mainly focussing on CV aspects, and the holistic changes following remission.

TRAIL REGISTRATION

ClinicalTrials.gov ( https://clinicaltrials.gov/ ) NCT03880513, registration date: 19 March 2019 (retrospectively registered). Protocol Date: 28 March 2014, Version 2.

B0 shimming of the human heart at 7T

PURPOSE

Inhomogeneities of the static magnetic B₀ field are a major limiting factor in cardiac MRI at ultrahigh field (≥ 7T), as they result in signal loss and image distortions. Different magnetic susceptibilities of the myocardium and surrounding tissue in combination with cardiac motion lead to strong spatio-temporal B₀ -field inhomogeneities, and their homogenization (B₀ shimming) is a prerequisite. Limitations of state-of-the-art shimming are described, regional B₀ variations are measured, and a methodology for spherical harmonics shimming of the B₀ field within the human myocardium is proposed.

METHODS

The spatial B₀ -field distribution in the heart was analyzed as well as temporal B₀ -field variations in the myocardium over the cardiac cycle. Different shim region-of-interest selections were compared, and hardware limitations of spherical harmonics B₀ shimming were evaluated by calibration-based B₀ -field modeling. The role of third-order spherical harmonics terms was analyzed as well as potential benefits from cardiac phase-specific shimming.

RESULTS

The strongest B₀ -field inhomogeneities were observed in localized spots within the left-ventricular and right-ventricular myocardium and varied between systolic and diastolic cardiac phases. An anatomy-driven shim region-of-interest selection allowed for improved B₀ -field homogeneity compared with a standard shim region-of-interest cuboid. Third-order spherical harmonics terms were demonstrated to be beneficial for shimming of these myocardial B₀ -field inhomogeneities. Initial results from the in vivo implementation of a potential shim strategy were obtained. Simulated cardiac phase-specific shimming was performed, and a shim term-by-term analysis revealed periodic variations of required currents.

CONCLUSION

Challenges in state-of-the-art B₀ shimming of the human heart at 7 T were described. Cardiac phase-specific shimming strategies were found to be superior to vendor-supplied shimming.

Clinical safety of ProMRI implantable cardioverter-defibrillator systems during head and lower lumbar magnetic resonance imaging at 1.5 Tesla

Magnetic resonance imaging (MRI) has long been contraindicated in patients with implanted pacemakers, defibrillators, and cardiac resynchronisation therapy (CRT) devices due to the risk of adverse effects through electromagnetic interference. Since many recipients of these devices will have a lifetime indication for an MRI scan, the implantable systems should be developed as ‘MRI-conditional’ (be safe for the MRI environment under predefined conditions). We evaluated the clinical safety of several Biotronik ProMRI (‘MRI-conditional’) defibrillator and CRT systems during head and lower lumbar MRI scans at 1.5 Tesla. The study enrolled 194 patients at 22 sites in Australia, Canada, and Europe. At ≥9 weeks after device implantation, predefined, non-diagnostic, specific absorption rate (SAR)-intensive head and lower lumbar MRI scans (total ≈30 minutes per patient) were performed in 146 patients that fulfilled pre-procedure criteria. Three primary endpoints were evaluated: freedom from serious adverse device effects (SADEs) related to MRI and defibrillator/CRT (leading to death, hospitalisation, life-threatening condition, or potentially requiring implanted system revision or replacement), pacing threshold increase, and sensing amplitude decrease, all at the 1-month post-MRI clinical visit. No MRI-related SADE occurred. Lead values remained stable, measured in clinic and monitored daily by the manufacturer home monitoring technology.

Myocardial infarction triggers cardioprotective antigen-specific T helper cell responses

T cell autoreactivity is a hallmark of autoimmune diseases but can also benefit self-maintenance and foster tissue repair. Herein, we investigated whether heart-specific T cells exert salutary or detrimental effects in the context of myocardial infarction (MI), the leading cause of death worldwide. After screening more than 150 class-II-restricted epitopes, we found that myosin heavy chain alpha (MYHCA) was a dominant cardiac antigen triggering post-MI CD4+ T cell activation in mice. Transferred MYHCA614-629-specific CD4+ T (TCR-M) cells selectively accumulated in the myocardium and mediastinal lymph nodes (med-LN) of infarcted mice, acquired a Treg phenotype with a distinct pro-healing gene expression profile, and mediated cardioprotection. Myocardial Treg cells were also detected in autopsies from patients who suffered a MI. Noninvasive PET/CT imaging using a CXCR4 radioligand revealed enlarged med-LNs with increased cellularity in MI-patients. Notably, the med-LN alterations observed in MI patients correlated with the infarct size and cardiac function. Taken together, the results obtained in our study provide evidence showing that MI-context induces pro-healing T cell autoimmunity in mice and confirms the existence of an analogous heart/med-LN/T cell axis in MI patients.

[Magnetic resonance imaging and active cardiac implants]

The combination of magnetic resonance imaging (MRI) and active cardiac implants, such as pacemakers and implantable cardioverter defibrillators (ICD) has been a challenge for electrophysiologists and imaging for many years. Diagnostic and therapeutic possibilities on the one hand and technical hazards on the other hand highlight the need for improvements and algorithms that enable a safe approach to these challenges. The advent of so-called MRI conditional implants provides safe procedures for at least some of the patients with an implant and the need for MRI. Recently published data encourage clinicians not to completely excluded an imaging modality as promising as MRI in clinically urgent cases in the presence of conventional implants. The interdisciplinary consensus paper of the German Society of Cardiology and the German Society of Radiology provides recommendations for these situations. This review article discusses these recommendations and provides an overview of the most recent publications with a focus on the long-term course of device parameters.

Detection of cardiac amyloidosis with 18F-Florbetaben-PET/CT in comparison to echocardiography, cardiac MRI and DPD-scintigraphy

PURPOSE

Cardiac amyloidosis (CA) is a rare cause of heart failure with frequently delayed diagnosis, because specific early signs or symptoms are missing. Recently, direct amyloid imaging using positron emission tomography/computed tomography (PET/CT) has emerged. The aim of this study was to examine the performance of ¹⁸F-florbetaben-PET/CT in detection of CA, and compare it to echocardiography (echo), cardiac MRI (CMR) and scintigraphy. Additionally, the use of ¹⁸F-florbetaben-PET/CT for quantification of amyloid burden and monitoring of treatment response was assessed.

METHODS

Twenty-two patients with proven (n = 5) or clinical suspicion (n = 17) of CA underwent ¹⁸F-florbetaben-PET/CT for diagnostic work-up. Qualitative and quantitative assessment including calculation of myocardial tracer retention (MTR) was performed, and compared to echo (n = 20), CMR (n = 16), scintigraphy (n = 16) and serologic biomarkers (NT-proBNP, cTnT, free light chains). In four patients, follow-up PET/CT was available (after treatment initiation, n = 3; surveillance, n = 1).

RESULTS

PET demonstrated myocardial ¹⁸F-florbetaben retention consistent with CA in 14/22 patients. Suspicion of CA was subsequently dropped in all eight PET-negative patients. Amyloid subtypes showed characteristic retention patterns (AL > AA > ATTR; all p < 0.005). MTR correlated with morphologic and functional parameters, as measured by CMR and echo (all r| > 0.47|, all p < 0.05), but not with cardiac biomarkers. Changes in MTR from baseline to follow-up corresponded well to treatment response, as assessed by cardiac biomarkers and performance status.

CONCLUSIONS

Imaging of cardiac amyloidosis (CA) with ¹⁸F-florbetaben-PET/CT is feasible and might be useful in differentiating CA subtypes.

Bioactive glass based scaffolds coated with gelatin for the sustained release of icariin

Gelatin-coated, 3D sponge-like scaffolds based on 45S5 bioactive glass were produced using the foam replication technique. Compressive strength tests of gelatin-coated samples compared to uncoated scaffolds showed significant strengthening and toughening effects of the gelatin coating with compressive strength values in the range of cortical bone. Additionally, the crosslinked gelatin network (using either caffeic acid or N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC)/N-hxdroxysuccinimide (NHS) as crosslinking agent) was shown to be a suitable candidate for the sustained release of the bioactive molecule icariin. Concerning bioactivity of the produced scaffolds, characterization by FTIR and SEM indicated the formation of hydroxyapatite (HA) in all samples after immersion in simulated body fluid (SBF) for 14 days, highlighting the favorable combination of mechanical robustness, bioactivity and drug delivery capability of this new type of scaffolds.

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Foam like bioactive glass scaffolds produced by replication technique.

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Gelatin coatings confer increased compression strength to scaffolds.

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Crosslinked gelatin coating is suitable candidate for the sustained release of icariin.

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Favorable combination of bioactivity, gelatin coating and icariin release demonstrated.

Associative effects between Arachis pintoi and dwarf elephantgrass hays on nutritional value in sheep

The aim of the present study was to evaluate the effect of including different levels of peanut (Arachis pintoi cv. Amarillo) hay (167 and 572 g/kg dry matter (DM) of crude protein and neutral detergent fibre respectively) on the nutritional value of diets based on dwarf elephantgrass (Pennisetum purpureum Shum, cv. Kurumi) hay (98 and 668 g/kg DM of crude protein and neutral detergent fibre respectively). Peanut hay was included in the proportions of 0.0, 0.33, 0.66 and 1.00 of total diet DM. Eight Texel × Suffolk crossbred wethers provided with duodenal cannula were assigned to the treatments in a replicated 4 × 4 Latin-square experiment. The organic matter (OM) intake increased linearly (P < 0.05) and the total apparent OM digestibility decreased linearly (P < 0.001) with an increasing inclusion of legume. The nitrogen (N) intake and N urinary excretion increased linearly (P < 0.05), whereas linear and quadratic responses were significant for digestible OM intake, N retention, and for the efficiency of rumen microbial protein synthesis. Cubic positive responses were significant (P < 0.05) for duodenal flow of total N, non-ammonia-N and rumen microbial-N. The inclusion of A. pintoi in dwarf elephantgrass-based diets improved the nutrient supply to sheep, but no additive effect was observed as a result of increasing the peanut proportion in the mixed diet.

Improved post-processing strategy for MOLLI based tissue characterization allows application in patients with dyspnoe and impaired left ventricular function

Contrast and non-contrast MRI based characterization of myocardium by T₁-mapping will be of paramount importance to obtain biomarkers, e.g. fibrosis, which determines the risk of heart failure patients. T₁-mapping by the standard post-processing of the modified look-locker inversion recovery (MOLLI) lacks of accuracy when trying to reduce its duration, which on the other hand, is highly desirable in patients with heart failure. The recently suggested inversion group fitting (IGF) technique, which considers more parameters for fitting, has a superior accuracy for long T₁ times despite a shorter duration. However, for short T₁ values, the standard method has a superior precision. A conditional fitting routine is proposed which ideally takes advantage of both algorithms.

MATERIALS AND METHODS

All measurements were performed on a 1.5T clinical scanner (ACHIEVA, Philips Healthcare, The Netherlands) using a MOLLI 5(n)3(n)3 prototype with n(heart beats) being a variable waiting time between inversion experiments. Phantom experiments covered a broad range of T₁ times, waiting times and heart rates. A saturation recovery experiment served as a gold standard for T₁ measurement. All data were analyzed with the standard MOLLI, the IGF fit and the conditional fitting routine and the obtained T₁ values were compared with the gold standard. In vivo measurements were performed in a healthy volunteer and a total of 34 patients with normal findings, dilative cardiomyopathy and amyloidosis.

RESULTS

Theoretical analysis and phantom experiments provided a threshold value for an apparent IGF T₁^* determining processing with IGF post processing for values above, or switching to the standard technique for values below. This was validated in phantoms and patients measurements. A reduction of the waiting time to 1 instead of 3 heart beats between the inversion experiments showed reliable results. The acquisition time was reduced from 17 to 13 heart beats. The in vivo measurements showed ECV values between 25% (18-33%; SD 0.03) in the healthy, 30% (22-40%; SD 0.04) in patients with DCM and 45% (30-60%; SD 0.9) in patients with amyloidosis.

CONCLUSION

The adopted post-processing algorithm determines long T₁ values with high accuracy and short T₁ values while maintaining a high precision. Based on reduction of waiting time, and independence of heart rate, it shortens breath hold duration and allows fast T₁-mapping, which is frequently a prerequisite in patients with cardiac diseases.

Somatostatin receptor based PET/CT in patients with the suspicion of cardiac sarcoidosis: an initial comparison to cardiac MRI

Diagnosis of cardiac sarcoidosis is often challenging. Whereas cardiac magnetic resonance imaging (CMR) and positron emission tomography/computed tomography (PET/CT) with 18F-fluorodeoxyglucose (FDG) are most commonly used to evaluate patients, PET/CT using radiolabeled somatostatin receptor (SSTR) ligands for visualization of inflammation might represent a more specific alternative. This study aimed to investigate the feasibility of SSTR-PET/CT for detecting cardiac sarcoidosis in comparison to CMR.15 patients (6 males, 9 females) with sarcoidosis and suspicion on cardiac involvement underwent SSTR-PET/CT imaging and CMR. Images were visually scored. The AHA 17-segment model of the left myocardium was used for localization and comparison of inflamed myocardium for both imaging modalities. In semi-quantitative analysis, mean (SUVmean) and maximum standardized uptake values (SUVmax) of affected myocardium were calculated and compared with both remote myocardium and left ventricular (LV) cavity.SSTR-PET was positive in 7/15, CMR in 10/15 patients. Of the 3 CMR+/PET- subjects, one patient with minor involvement (<25% of wall thickness in CMR) was missed by PET. The remaining two CMR+/PET- patients displayed no adverse cardiac events during follow-up.In the 17-segment model, PET/CT yielded 27 and CMR 29 positive segments. Overall concordance of the 2 modalities was 96.1% (245/255 segments analyzed). SUVmean and SUVmax in inflamed areas were 2.0±1.2 and 2.6±1.2, respectively. The lesion-to-remote myocardium and lesion-to-LV cavity ratios were 1.8±0.2 and 1.9±0.2 for SUVmean and 2.0±0.3 and 1.7±0.3 for SUVmax, respectively.Detection of cardiac sarcoidosis by SSTR-PET/CT is feasible. Our data warrant further analysis in larger prospective series.

MRI-guided ablation of wide complex tachycardia in a univentricular heart

Magnetic resonance imaging can be used for preprocedural assessment of complex anatomy for radiofrequency (RF) ablations, e.g., in a univentricular heart. This case report features the treatment of a young patient with a functionally univentricular heart who suffered from persistent sudden onset tachycardia with wide complexes that required RF ablation as treatment.

Minimizing risk of nephrogenic systemic fibrosis in cardiovascular magnetic resonance

Nephrogenic Systemic Fibrosis is a rare condition appearing only in patients with severe renal impairment or failure and presents with dermal lesions and involvement of internal organs. Although many cases are mild, an estimated 5% have a progressive debilitating course. To date, there is no known effective treatment thus stressing the necessity of ample prevention measures. An association with the use of Gadolinium based contrast agents (GBCA) makes Nephrogenic Systemic Fibrosis a potential side effect of contrast enhanced magnetic resonance imaging and offers the opportunity for prevention by limiting use of gadolinium based contrast agents in renal failure patients. In itself toxic, Gadolinium is embedded into chelates that allow its safe use as a contrast agent. One NSF theory is that Gadolinium chelates distribute into the extracellular fluid compartment and set Gadolinium ions free, depending on multiple factors among which the duration of chelates exposure is directly related to the renal function. Major medical societies both in Europe and in North America have developed guidelines for the usage of GBCA. Since the establishment of these guidelines and the increased general awareness of this condition, the occurrence of NSF has been nearly eliminated. Giving an overview over the current knowledge of NSF pathobiochemistry, pathogenesis and treatment options this review focuses on the guidelines of the European Medicines Agency, the European Society of Urogenital Radiology, the FDA and the American College of Radiology from 2008 up to 2011 and the transfer of this knowledge into every day practice.

Direct cooling of the catheter tip increases safety for CMR-guided electrophysiological procedures

BACKGROUND

One of the safety concerns when performing electrophysiological (EP) procedures under magnetic resonance (MR) guidance is the risk of passive tissue heating due to the EP catheter being exposed to the radiofrequency (RF) field of the RF transmitting body coil. Ablation procedures that use catheters with irrigated tips are well established therapeutic options for the treatment of cardiac arrhythmias and when used in a modified mode might offer an additional system for suppressing passive catheter heating.

METHODS

A two-step approach was chosen. Firstly, tests on passive catheter heating were performed in a 1.5 T Avanto system (Siemens Healthcare Sector, Erlangen, Germany) using a ASTM Phantom in order to determine a possible maximum temperature rise. Secondly, a phantom was designed for simulation of the interface between blood and the vascular wall. The MR-RF induced temperature rise was simulated by catheter tip heating via a standard ablation generator. Power levels from 1 to 6 W were selected. Ablation duration was 120 s with no tip irrigation during the first 60 s and irrigation at rates from 2 ml/min to 35 ml/min for the remaining 60 s (Biotronik Qiona Pump, Berlin, Germany). The temperature was measured with fluoroscopic sensors (Luxtron, Santa Barbara, CA, USA) at a distance of 0 mm, 2 mm, 4 mm, and 6 mm from the catheter tip.

RESULTS

A maximum temperature rise of 22.4°C at the catheter tip was documented in the MR scanner. This temperature rise is equivalent to the heating effect of an ablator's power output of 6 W at a contact force of the weight of 90 g (0.883 N). The catheter tip irrigation was able to limit the temperature rise to less than 2°C for the majority of examined power levels, and for all examined power levels the residual temperature rise was less than 8°C.

CONCLUSION

Up to a maximum of 22.4°C, the temperature rise at the tissue surface can be entirely suppressed by using the catheter's own irrigation system. The irrigated tip system can be used to increase MR safety of EP catheters by suppressing the effects of unwanted passive catheter heating due to RF exposure from the MR scanner.

First observation of electrorheological plasmas

We report the experimental discovery of "electrorheological (ER) complex plasmas," where the control of the interparticle interaction by an externally applied electric field is due to distortion of the Debye spheres that surround microparticles (dust) in a plasma. We show that interactions in ER plasmas under weak ac fields are mathematically equivalent to those in conventional ER fluids. Microgravity experiments, as well as molecular dynamics simulations, show a phase transition from an isotropic to an anisotropic (string) plasma state as the electric field is increased.

Working aboard the Mir space station

For more than ten years, the Mir station has been the World's only permanently manned laboratory in low earth orbit. With an orbital inclination of 51.6 degrees, its ground track covers more than 85% of the Earth's surface, where approximately 95% of the population lives. For the transfer of up to three crew members per trip to and from Mir, the 6.9 t Soyuz spacecraft is used. In general, the station's crew is changed every six months, with an overlap during the exchange of between one and two weeks. A Progress spacecraft (an unmanned derivative of the Soyuz vehicle) visits the station every three months to resupply it, with up to 2.1 t of payload, and to reboost it to maintain its nominal orbital altitude. The station's core module, injected into orbit in February 1986, contains the central control post for most onboard systems, the computer for attitude control, and the telemetry and communications system. It also contains the station's largest work space, which is 7.0 m long and varies in width between 1.5 and 2.5 m.

Cell-cycle-dependent expression of DNA primase activity

Protein extracts were prepared at various times after serum stimulation of growth-arrested mouse 3T3 fibroblasts. The extracts were fractionated by sucrose gradient centrifugation and used to determine the activities of DNA polymerase alpha and DNA primase. We found that polymerase and primase appeared in close association in one homogeneous 8.2-S peak. Neither polymerase, free of associated primase, nor primase, free of polymerase, could be detected at any time after serum stimulation. The activities of both enzymes started to increase concomitantly at the beginning of the DNA replication phase of the cell cycle. We found five to six times more DNA primase activity in replicating than in resting 3T3 cells. Besides DNA primase, a second additional priming activity could be detected. This activity sedimented at 12.5 S and corresponded most probably to RNA polymerase I.

Synthesis of DNA polymerase alpha analyzed by immunoprecipitation from synchronously proliferating cells

Synchronously proliferating TC7 monkey and 3T3 mouse cells were pulse labeled with [35S]methionine. Radioactively labeled DNA polymerase alpha was immunoprecipitated with polymerase-specific monoclonal antibodies. The precipitated polypeptides were identified by gel electrophoresis and fluorography. The increase in DNA polymerase alpha activity during S phase was accompanied by an increased synthesis of the enzyme. Some DNA polymerase alpha was synthesized in growth-arrested TC7 cells whereas the synthesis of the large polymerase subunit in 3T3 cells was strictly coupled to the replicative phase of the cell cycle. We also found that DNA polymerase alpha was more prone to proteolysis in TC7 cells than in 3T3 cells. In 3T3 cells, a polymerase subunit with an apparent molecular weight of 186 000 was observed; this subunit was most probably associated with two smaller subunits of Mr 74 000 and 52 000. Synthesis of these three polymerase-associated polypeptides appeared to be regulated differently.

Shape-dependent regulation of cytoskeletal protein synthesis in anchorage-dependent and anchorage-independent cells

We examine changes in protein synthesis that accompany suspension (i.e. shape alteration) of anchorage-dependent and anchorage-independent cells using a newly developed cell fractionation procedure based on detergent extraction. Using this procedure, a cell can be divided into four distinct and independent fractions: soluble, cytoskeleton, chromatin and nuclear matrix-intermediate filament. This fractionation procedure is used to investigate protein synthetic events associated with the release from anchorage-dependent growth, characteristic of transformed cells. Suspension results in several unexpected events in both anchorage-dependent (3T3) cells and anchorage-independent (SVPy 3T3) cells. Suspension of 3T3 cells results in a reduction of total protein synthesis; however, two proteins are enhanced in their amount of synthesis. Suspension of SVPy 3T3 results in about 20 proteins proceeding through short and long-term alterations in the rate of synthesis. The synthesis of some of these proteins is inhibited, others undergo a transient decrease in synthesis upon suspension and then increase above their rate in the anchored state, while the synthesis of others steadily increases after suspension. Suspension of anchorage-dependent cells results in a fraction specific shift in the rates of protein synthesis. Possible roles for these fraction-specific proteins are considered.

"Prompt" heat shock proteins: translationally regulated synthesis of new proteins associated with the nuclear matrix-intermediate filaments as an early response to heat shock

The response of mammalian cells, such as HeLa cells, to prolong exposure to increased temperature (termed heat shock) has been well characterized. In these studies new mRNA is synthesized for several proteins whose translation is best seen after a return to 37 degrees C. We show here another response to increased temperature of a distinctively different character. A set of at least 50 newly detectable proteins, exclusively associated with the nuclear matrix-intermediate filaments (NM-IF) fraction, is synthesized immediately upon exposure to high temperature. These are of very low abundance or nonexistent in the unstressed cell and none appear to correspond to the "classic" heat shock proteins produced after new transcription. Prior treatment with actinomycin D has little effect on these "prompt" proteins, and they appear to be made from preexisting mRNAs that are activated at the increased temperature. The protein synthesis in the soluble, cytoskeletal, and chromatin fractions is strongly reduced by the increased temperature, while the labeling of the prompt proteins associated with NM-IF complex rapidly rises severalfold above that in control cells. Additionally these results suggest that the four cell fractions are not arbitrary cell divisions; rather they represent physiologically significant compartments in the cell.

Initiation of adenovirus DNA replication

In an attempt to study the mechanism of initiation of adenovirus DNA replication, an assay was developed to investigate the pattern of DNA synthesis in early replicative intermediates of adenovirus DNA. By using wild-type virus-infected cells, it was possible to place the origin of adenovirus type 2 DNA replication within the terminal 350 to 500 base pairs from either of the two molecular termini. In addition, a variety of parameters characteristic of adenovirus DNA replication were compared with those obtained in a soluble nuclear extract competent for viral DNA replication. It was observed that in vitro DNA replication, which is dependent on the exogenously added viral DNA-protein complex as its optimal template, occurs in a manner apparently indistinguishable from the situation in virus-infected cells. This includes the presence of proteinaceous material on the molecular termini of newly initiated viral DNA.