ECG-gated Phase Contrast Research Articles

Demonstration of circumferential heterogeneity in displacement and strain in the abdominal aortic wall by spiral cine DENSE MRI.

Knowledge of tissue properties of the abdominal aorta can improve understanding of vascular disease and guide interventional approaches. Existing MRI methods to quantify aortic wall displacement and strain are unable to discern circumferential heterogeneity. To assess regional variation in abdominal aortic wall displacement and strain as a function of circumferential position using spiral cine displacement encoding with stimulated echoes (DENSE). Prospective. Cardiovascular disease-free men (n = 8) and women (n = 9) ages 30-42. Prospective electrocardiogram (ECG)-gated and navigator echo-gated spiral, cine 2D DENSE and retrospective ECG-gated phase contrast MR (PCMR) sequences at 3T. In-plane displacement values of the aortic wall acquired with DENSE were used to determine radial and circumferential aortic wall motion. A quadrilateral-based 2D strain calculation method was implemented to determine strain from the displacement field. Peak displacement and its radial and circumferential contributions as well as peak circumferential strain were compared among eight circumferential wall segments. Distensibility was calculated using PCMR and compared with homogenized circumferential strain. To account for repeated measurements in volunteers, linear mixed models for mean sector values were created for displacement magnitude, circumferential displacement, radial displacement, and circumferential strain. Comparisons were made between sectors. Calculated distensibility and homogenized circumferential strain were compared using Bland-Altman analysis. Statistical significance was defined as P < 0.05. Displacement was highest in the anterior wall (1.5 ± 0.7 mm) and was primarily in the radial as compared with circumferential direction (1.04 ± 0.05 mm vs. 0.81 ± 0.42 mm). Circumferential strain was highest in the lateral walls (left 0.16 ± 0.05 and right 0.21 ± 0.12) with homogenized circumferential strain of 0.14 ± 0.05. DENSE imaging in the abdominal aortic wall demonstrated that the anterior aortic wall exhibits the greatest displacement, while the lateral wall experiences the largest circumferential strain. 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:731-743.

Impact of cardiac arrhythmia on velocity quantification by ECG gated phase contrast MRI

Background Blood flow quantification using ECG gated phase contrast (PC) MRI has proven to be a useful clinical tool for the evaluation of cardiovascular pathologies such aortic valve disease or cardiac shunts. However, data are acquired in an ECG synchronized manner over multiple heart beats and the impact of cardiac arrhythmia, which can frequently be encountered in patients with atrial fibrillation (AF), on flow parameters is unclear. To assess the impact of arrhythmia and thus RR interval variability on ECG-gated PC MRI acquisitions we have performed a simulation study to systematically investigate the impact of beat-to-beat variations on ECG gated multi-beat flow imaging with MRI using real time invivo TEE data in 5 AF patients with known arrhythmia.

A qualitative and quantitative assessment of cardiac cine Phase contrast MRI: comparison of image quality between 2D and 3D acquisition

Background 3D and gapless multi-slice 2D cine Phase contrast (PC) MRI enables the visualization and analysis of 4D (3D + time) intracardiac flow. However, the image quality which affects the accuracy of segmentation of left ventricle (LV) has not been discussed. In this study, we compared the magnitude image and the source image of PC MR angiography (MagSUM) derived from both 2D and 3D PC MRI. For the qualitative analysis, we assessed the image quality for the delineation of endocardial border. And we measured LV volume and compared with standard cine MRI for the quantitative analysis. Methods Ten healthy volunteer (all male, median age: 24 years) underwent 2D and 3D prospectively ECG-gated PC MRI with respiratory naviation on 3T MRI (Trio a Tim, Siemens AG Healthcare Sector, Erlangen, Germany).The short axial plane was employed to cover left ventricle. The common parameters for PC MRI were: VENC = 150 cm/ sec, segmentation factor = 2 to 3, reconstruction phase = 12 to 14 according to R-R interval. The acquisition voxel of 2D and 3D PC MRI were reconstructed into 2.1x2.1x5 mm and 2.1x2.1x2.1 mm, respectively. Standard 2D retrospectively ECG-gated cine MRI was reconstructed to 2.1x1.8x8 mm. Two readers discussed and determined the

P07 Splanchnic steal in patients with liver disease: a 3T MRI study of visceral blood flow

IntroductionLiver cirrhosis and the development of portal hypertension is associated with significant morbidity and mortality. It is widely accepted that patients with liver disease have a hyperdynamic circulation that is...

Flow measurement by cardiovascular magnetic resonance: a multi-centre multi-vendor study of background phase offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements.

AimsCardiovascular magnetic resonance (CMR) allows non-invasive phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the offset error. We studied the severity of uncorrected velocity offset errors across sites and CMR systems.Methods and ResultsIn a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of offsets were implemented. The greatest uncorrected velocity offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement.ConclusionIn the absence of hardware or software upgrades able to reduce phase offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of offset correction software will still need testing with respect to clinical flow acquisitions.

Studies on developments of imaging and analytical methods and evaluations of properties mainly on image quality in MRI (in Japanese)

The aims of this thesis were to develop imaging and analytical methods in magnetic resonance imaging (MRI) to obtain morphological and functional information of the human body and to evaluate image quality of an MRI system. Various new methods are illustrated. A fast imaging method for obtaining a T1‐weighted image by using the rapid acquisition relaxation enhanced sequence combined with the variable flip angle excitation is described. Next, the thesis describes a method for performing a dynamic contrast‐enhanced T1‐weighted and study simultaneously to evaluate regional hemodynamics in brain tumors. This method can increase the amount of vascular information and reveals the hemodynamics of the brain tumor and surrounding regions in greater detail. The thesis describes a frequency analysis of cerebrospinal fluid (CSF) flow measured with an ECG gated phase contrast cine‐MRI to clarify the flow dynamics of intracranial CSF in normal pressure hydrocephalus (NPH). This frequency analysis can noninvasively provide a picture of the pathophysiology of NPH and of intracranial changes. Developments of the above imaging and analytical methods in MRI make it possible to obtain more detailed information on the human body. In addition, the thesis describes a new method to accurately measure the modulation transfer function and the signal‐to‐noise ratio in the positive and negative frequencies in MRI with a specially designed phantom. This evaluation method makes it possible to obtain more detail on the image quality of MRI, and is useful in various performance assessments such as the evaluation of pulse sequences.

MR-tomographische Liquorflußmessungen im Aquädukt

The aim of this study was to measure oscillating CSF flow in the mesencephalic aqueduct and to obtain normal values for the systolic-diastolic flow amplitude and systolic stroke volume.28 healthy volunteers of different age groups (10 to 75 years, median 45 years) were examined using an ECG-gated phase contrast sequence.From the oscillating flow we calculated 1. the systolic-diastolic flow amplitude and 2. the systolic stroke volume. There was a high interindividual variability: The 25th percentile/median/75th percentile were 0.20/0.30/0.45 ml/s for flow amplitude and 22/38/53 μl for stroke volume. Age correlated positively with the values. The high interindividual variability of normal values indicates difficulties in sensitivity and specificity examinating disturbances of CSF dynamics.