[Show abstract][Hide abstract] ABSTRACT: Objective:
The aim of this study was to evaluate the potential of contrast media (CM) reduction in computed tomography angiography (CTA) of coronary artery bypass grafts (CABGs) when adapting CM volume to automatically selected tube voltages.
Material and methods:
Sixty consecutive patients (mean age, 71 ± 14.5 years) with a total of 176 CABGs (692 bypass segments) underwent contrast-enhanced prospectively electrocardiography-gated high-pitch CTA with automated, attenuation-based tube voltage selection (100 ref. peak kilovoltage [kVp], 200 ref. mAs, tube voltages from 70-150 kVp in 10-kVp steps) using a third-generation 192-slice dual-source computed tomography scanner. Volume and flow of CM (370 mg/mL iodine) was adapted according to the tube voltages using iodine attenuation-curves derived from a foregoing phantom study. In patients, CM volumes ranged from 80 mL (flow rate, 7 mL/s) at 120 kVp to 48 mL (flow rate, 4.2 mL/s) at 80 kVp. Two independent, blinded readers evaluated subjective image quality of the proximal anastomosis, bypass graft, distal anastomosis, and postanastomotic native coronary artery using a 3-point Likert scale. Objective image quality (attenuation of graft and noise) was determined and contrast-to-noise ratio (CNR) was calculated. Volume computed tomography dose index and dose-length product of each CTA examination were noted. Cohen κ was used to define interreader agreement of subjective image quality. Regression analysis was used to determine relationships between tube voltage and vascular attenuation, image noise, and CNR.
Using attenuation-based tube voltage selection, 5 patients (8%) were scanned at 80 kVp, 22 (37%) at 90 kVp, 11 (18%) at 100 kVp, 10 (17%) at 110 kVp, and 12 (20%) at 120 kVp. Agreement in subjective image quality between readers was good (κ = 0.678). Diagnostic image quality was achieved in 679 of 692 (98%) bypass segments in 169 of 176 bypass grafts (96%). Thirteen of 692 bypass segments (2%) in 7 of 176 bypass grafts (4%) were rated as nondiagnostic because of severe artifacts caused by motion or beam hardening (2 proximal anastomoses of sequential bypasses, 3 graft bodies, 5 distal anastomoses, and 3 postanastomotic coronary artery segments). Regression analysis revealed no significant relationship between the automatically selected tube voltages and objective image quality parameters (bypass graft attenuation: P = 0.315; noise: P = 0.433; and CNR: P = 0.168), indicating homogenous attenuation, noise, and CNR across tube voltage levels. Mean volume computed tomography dose index was 4.0 ± 0.9 mGy, and mean dose length product was 135.0 ± 29.6 mGy*cm.
Adapting CM protocols to automatically selected tube voltage levels allows for low-volume CM CTA examinations of CABG grafts with diagnostic image quality.
No preview · Article · Dec 2015 · Investigative radiology
[Show abstract][Hide abstract] ABSTRACT: Quantification of myocardial perfusion from first-pass cardiovascular magnetic resonance (CMR) images at high contrast agent (CA) dose requires separate acquisition of blood pool and myocardial tissue enhancement. In this study, a dual-sequence approach interleaving 2D imaging of the arterial input function with high-resolution 3D imaging for myocardial perfusion assessment is presented and validated for low and high CA dose.
A dual-sequence approach interleaving 2D imaging of the aortic root and 3D imaging of the whole left ventricle using highly accelerated k-t PCA was implemented. Rest perfusion imaging was performed in ten healthy volunteers after administration of a Gadolinium-based CA at low (0.025 mmol/kg b.w.) and high dose (0.1 mmol/kg b.w.). Arterial input functions extracted from the 2D and 3D images were analysed for both doses. Myocardial contrast-to-noise ratios (CNR) were compared across volunteers and doses. Variations of myocardial perfusion estimates between volunteers and across myocardial territories were studied.
High CA dose imaging resulted in strong non-linearity of the arterial input function in the 3D images at peak CA concentration, which was avoided when the input function was derived from the 2D images. Myocardial CNR was significantly increased at high dose compared to low dose, with a 2.6-fold mean CNR gain. Most robust myocardial blood flow estimation was achieved using the arterial input function extracted from the 2D image at high CA dose. In this case, myocardial blood flow estimates varied by 24 % between volunteers and by 20 % between myocardial territories when analysed on a per-volunteer basis.
Interleaving 2D imaging for arterial input function assessment enables robust quantitative 3D myocardial perfusion imaging at high CA dose.
Preview · Article · Dec 2015 · Journal of Cardiovascular Magnetic Resonance
[Show abstract][Hide abstract] ABSTRACT: Left ventricular thrombus (LVT) formation may worsen the post-infarct outcome as a result of thromboembolic events. It also complicates the use of modern antiplatelet regimens, which are not compatible with long-term oral anticoagulation. The knowledge of the incidence of LVT may therefore be of importance to guide antiplatelet and antithrombotic therapy after acute myocardial infarction (AMI).
In 177 patients with large, mainly anterior AMI, standard cardiac magnetic resonance imaging (CMR) including cine and late gadolinium enhancement (LGE) imaging was performed shortly after AMI as per protocol. CMR images were analysed at an independent core laboratory blinded to the clinical data. Transthoracic echocardiography (TTE) was not mandatory for the trial, but was performed in 64% of the cases following standard of care. In a logistic model, 3 out of 61 parameters were used in a multivariable model to predict LVT.
LVT was detected by use of CMR in 6.2% (95% confidence interval [CI] 3.1%-10.8%). LGE sequences were best to detect LVT, which may be missed in cine sequences. We identified body mass index (odds ratio 1.18; p = 0.01), baseline platelet count (odds ratio 1.01, p = 0.01) and infarct size as assessed by use of CMR (odds ratio 1.03, p = 0.02) as best predictors for LVT. The agreement between TTE and CMR for the detection of LVT is substantial (kappa = 0.70).
In the current analysis, the incidence of LVT shortly after AMI is relatively low, even in a patient population at high risk. An optimal modality for LVT detection is LGE-CMR but TTE has an acceptable accuracy when LGE-CMR is not available.
Full-text · Article · Jun 2015 · Schweizerische medizinische Wochenschrift
[Show abstract][Hide abstract] ABSTRACT: Purpose To evaluate the potential of advanced modeled iterative reconstruction (ADMIRE) for optimizing radiation dose of high-pitch coronary CT angiography (CCTA). Methods High-pitch 192-slice dual-source CCTA was performed in 25 patients (group 1) according to standard settings (ref. 100 kVp, ref. 270 mAs/rot). Images were reconstructed with filtered back projection (FBP) and ADMIRE (strength levels 1–5). In another 25 patients (group 2), high-pitch CCTA protocol parameters were adapted according to results from group 1 (ref. 160 mAs/rot), and images were reconstructed with ADMIRE level 4. In ten patients of group 1, vessel sharpness using full width at half maximum (FWHM) analysis was determined. Image quality was assessed by two independent, blinded readers. Results Interobserver agreements for attenuation and noise were excellent (r = 0.88/0.85, p p p Conclusions In a selected population, ADMIRE can be used for optimizing high-pitch CCTA to an effective dose of 0.3 mSv.
• Advanced modeled IR (ADMIRE) reduces image noise up to 50 % as compared to FBP. • Coronary artery vessel borders show an increasing sharpness at higher ADMIRE levels. • High-pitch CCTA with ADMIRE is possible at a radiation dose of 0.3 mSv.
No preview · Article · Jun 2015 · European Radiology
[Show abstract][Hide abstract] ABSTRACT: Background-First-pass myocardial perfusion cardiovascular magnetic resonance (CMR) imaging yields high diagnostic accuracy for the detection of coronary artery disease (CAD). However, standard 2D multislice CMR perfusion techniques provide only limited cardiac coverage, and hence considerable assumptions are required to assess myocardial ischemic burden. The aim of this prospective study was to assess the diagnostic performance of 3D myocardial perfusion CMR to detect functionally relevant CAD with fractional flow reserve (FFR) as a reference standard in a multicenter setting. Methods and Results-A total of 155 patients with suspected CAD listed for coronary angiography with FFR were prospectively enrolled from 5 European centers. 3D perfusion CMR was acquired on 3T MR systems from a single vendor under adenosine stress and at rest. All CMR perfusion analyses were performed in a central laboratory and blinded to all clinical data. One hundred fifty patients were successfully examined (mean age 62.9+/-10 years, 45 female). The prevalence of CAD defined by FFR (<0.8) was 56.7% (85 of 150 patients). The sensitivity and specificity of 3D perfusion CMR were 84.7% and 90.8% relative to the FFR reference. Comparison to quantitative coronary angiography (>= 50%) yielded a prevalence of 65.3%, sensitivity and specificity of 76.5% and 94.2%, respectively. Conclusions-In this multicenter study, 3D myocardial perfusion CMR proved highly diagnostic for the detection of significant CAD as defined by FFR.
Full-text · Article · Mar 2015 · Circulation Cardiovascular Imaging
[Show abstract][Hide abstract] ABSTRACT: Since the discovery of the obese (ob) gene product leptin, fat has been considered an endocrine organ. Especially epicardial fat has gained increasing attention in recent years. The epicardial fat plays a major role in fat metabolism; however, harmful properties have also been reported. Echocardiography, computed tomography and cardiac magnetic resonance imaging are the non-invasive tools used to measure epicardial fat volume. This review briefly introduces the basic physiological and pathophysiological considerations concerning epicardial fat. The main issue of this review is the presentation of non-invasive measurement techniques of epicardial fat using various imaging modalities and a literature overview of associations between epicardial fat and common cardiovascular diseases.
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVES: To describe the use of a new extracellular matrix patch as a means for atrial reconstruction in patients with cardiac tumours.
METHODS: A new extracellular matrix patch was used to reconstruct atrial and neighbouring structures after tumour resections. In 1 case, it was used to reconstruct the atrial septum and the left atrial roof after excision of a huge myxoma. In a second case, it was used to reconstruct the right atrium, including the superior vena cava after excision of a primary cardiac sarcoma. In a third case, it was used to reconstruct both atria, the right-sided pulmonary venous confluence and the roof of the coronary sinus after excision of a metastasis of malignant melanoma.
RESULTS: In all cases, reconstruction was successful and facilitated because of the flexible and thin character of the extracellular matrix, which also seemed to be advantageous with regards to haemostasis.
CONCLUSIONS: Extracellular matrix patches are a potential alternative for pericardial patches for complex reconstructions of atrial structures because of their pliable characteristics and consecutively reduced need for haemostatic stitches.
Full-text · Article · Sep 2014 · Interactive Cardiovascular and Thoracic Surgery
[Show abstract][Hide abstract] ABSTRACT: Purpose
In this work we present a dual-phase diffusion tensor imaging (DTI) technique that incorporates a correction scheme for the cardiac material strain, based on 3D myocardial tagging.
In vivo dual-phase cardiac DTI with a stimulated echo approach and 3D tagging was performed in 10 healthy volunteers. The time course of material strain was estimated from the tagging data and used to correct for strain effects in the diffusion weighted acquisition. Mean diffusivity, fractional anisotropy, helix, transverse and sheet angles were calculated and compared between systole and diastole, with and without strain correction. Data acquired at the systolic sweet spot, where the effects of strain are eliminated, served as a reference.
The impact of strain correction on helix angle was small. However, large differences were observed in the transverse and sheet angle values, with and without strain correction. The standard deviation of systolic transverse angles was significantly reduced from 35.9±3.9° to 27.8°±3.5° (p<0.001) upon strain-correction indicating more coherent fiber tracks after correction. Myocyte aggregate structure was aligned more longitudinally in systole compared to diastole as reflected by an increased transmural range of helix angles (71.8°±3.9° systole vs. 55.6°±5.6°, p<0.001 diastole). While diastolic sheet angle histograms had dominant counts at high sheet angle values, systolic histograms showed lower sheet angle values indicating a reorientation of myocyte sheets during contraction.
An approach for dual-phase cardiac DTI with correction for material strain has been successfully implemented. This technique allows assessing dynamic changes in myofiber architecture between systole and diastole, and emphasizes the need for strain correction when sheet architecture in the heart is imaged with a stimulated echo approach.
[Show abstract][Hide abstract] ABSTRACT: Fett wird seit der Entdeckung des ob-Gen-Produkts Leptin als endokrines Organ angesehen. Insbesondere dem epikardialen Fett ist in den letzten Jahren vermehrte Aufmerksamkeit geschenkt worden. Das epikardiale Fett nimmt Aufgaben im Fettmetabolismus wahr, jedoch werden ihm auch schädliche parakrine, autokrine und systemische Wirkungen zugeschrieben. Die bildmorphologische Bestimmung des epikardialen Fettvolumens gelingt mittels der Echokardiographie, der Computertomographie oder der Magnetresonanztomographie. In diesem Review sollen zunächst grundlegende Betrachtungen der Physiologie und Pathophysiologie des epikardialen Fetts skizziert werden. Der Schwerpunkt des Reviews liegt dann auf der Vorstellung der Messmethoden des epikardialen Fetts mittels der einzelnen Bildgebungsmodalitäten und einem Literaturüberblick der Assoziationen des epikardialen Fetts zu Erkrankungen des kardiovaskulären Systems wie dem metabolischen Syndrom, der Herzinsuffizienz und der koronaren Herzkrankheit.
Since the discovery of the obese (ob) gene product leptin, fat has been considered an endocrine organ. Especially epicardial fat has gained increasing attention in recent years. The epicardial fat plays a major role in fat metabolism; however, harmful properties have also been reported. Echocardiography, computed tomography and cardiac magnetic resonance imaging are the non-invasive tools used to measure epicardial fat volume. This review briefly introduces the basic physiological and pathophysiological considerations concerning epicardial fat. The main issue of this review is the presentation of non-invasive measurement techniques of epicardial fat using various imaging modalities and a literature overview of associations between epicardial fat and common cardiovascular diseases.