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Non-Cartesian sampling: Spiral and Radial. a) Spiral k-space trajectory with two interleaves, the centre and edge of one interleave is zoomed in on the left. Below is shown a sequence diagram of the acquisition of one spiral interleave. b) Radial trajectory. Below is shown a sequence diagram for the acquisition of two radial lines.
Source publication
The multitude of applications offered by CMR make it an increasing popular modality to study the heart and the surrounding vessels. Nevertheless the anatomical complexity of the chest, together with cardiac and respiratory motion, and the fast flowing blood, present many challenges which can possibly translate into imaging artefacts. The literature...
Contexts in source publication
Context 1
... sampling can also have non-cartesian trajec- tories, with the most common being spiral or radial. In a spiral acquisition each k-space line follows a spiral tra- jectory (Figure 7a), this is efficient in the sense that it achieves a greater coverage of k-space with fewer shots than Cartesian. Also a spiral acquisition collects a circu- lar area of k-space and therefore ignores the corners of k-space which are collected with a Cartesian acquisition but don't necessarily contribute to the final image. ...Context 2
... requirements are used to define the gradient waveform, although due to hardware limitations the gradients cannot reach their maximum amplitudes immediately from the beginning, and instead the amplitude is ramped up during the first few cycles. The result of this is an oversampling of data in the centre of k-space, with a higher density of data points than in the edges (Figure 7a). ...Context 3
... sampling was the first k-space sampling tra- jectory to be used in MRI with a backprojection image reconstruction [11], analogous to Computed Tomog- raphy. In a radial trajectory the k-space is sampled with radial spokes that pass through the centre of k-space (Figure 7b). Image reconstruction in radial sampling can either be with a back projection algorithm or, most commonly, gridded into a Cartesian matrix which is then reconstructed as Cartesian data. ...Context 4
... for example, motion only occurred when sampling the edges of k-space, then motion artefacts would result in blurring of the edges of the moving object in the phase encoding direction. If, on the other hand, the central regions of k-space were affected then this would result in a more significant ghosting and image degradation ( Figure 17). In general if breathing motion is periodic during the acquisition of k-space in the phase encode direction, it results in a number of defined "ghost" arte- facts distributed in that direction on the image. ...Context 5
... general if breathing motion is periodic during the acquisition of k-space in the phase encode direction, it results in a number of defined "ghost" arte- facts distributed in that direction on the image. As can be seen from Figure 17, for acquisition sequences that employ an interleaved segmented coverage of k-space then a single movement or drift in the respiratory pos- ition will have a similar impact to periodic breathing motion. On the other hand for sequences that acquire k-space in a block sequential manner a single move- ment, as long as it doesn't coincide with the centre of k- space, or similarly a drift in position, will cause some blurring but will generally cause less impact through ghosting. ...Similar publications
Background:
The associations between cardiovascular disease (CVD) risk factors and the biventricular geometry of the right ventricle (RV) and left ventricle (LV) have been difficult to assess, due to subtle and complex shape changes. We sought to quantify reference RV morphology as well as biventricular variations associated with common cardiovasc...
Background:
Myopericardial inflammation, perfusion's defects and fibrosis are major causes of cardiac disease in scleroderma (SSc). We hypothesized that using inflammation and stress perfusion-fibrosis cardiovascular magnetic resonance (CMR), we can identify the pathophysiology of heart disease in asymptomatic diffuse SSc.
Patients-methods:
46 r...
Background Intramyocardial hemorrhage (IMH) identified by CMR is an established prognostic marker following acute myocardial infarction (AMI), but remains relatively underused in the clinical setting. Detection of IMH by T2-weighted or T2* CMR can be limited by long breath hold times and sensitivity to artefacts, especially at 3 Tesla. Alternative...
Background
Computed tomography angiography (CTA) or contrast-enhanced (CE) cardiovascular magnetic resonance angiography (CMRA) is often obtained in patients with atrial fibrillation undergoing evaluation prior to pulmonary vein (PV) isolation. Drawbacks of CTA include radiation exposure and potential risks from iodinated contrast agent administrat...
Background:
Breath-hold (BH) requirement remains the limiting factor on the spatio-temporal resolution and coverage of the cine balanced steady-state free precession (bSSFP) cardiovascular magnetic resonance (CMR) imaging. In this prospective two-center clinical trial, we validated the performance of a respiratory triggered (RT) bSSFP cine sequenc...
Citations
... There have been a number of studies on segmentation algorithms have achieved good segmentation results [28,29]. However, CMR images are susceptible to noise and artefacts [30], which can reduce the accuracy of automatic segmentation and radiomics analysis. Stochastic resonance can be used to improve the contrast by using the noise in the image, so that more accurate segmentation can be performed [31,32]. ...
Background
The prevalence of hypertensive heart disease (HHD) is high and there is currently no easy way to detect early HHD. Explore the application of radiomics using cardiac magnetic resonance (CMR) non-enhanced cine sequences in diagnosing HHD and latent cardiac changes caused by hypertension.
Methods
132 patients who underwent CMR scanning were divided into groups: HHD (42), hypertension with normal cardiac structure and function (HWN) group (46), and normal control (NOR) group (44). Myocardial regions of the end-diastolic (ED) and end-systolic (ES) phases of the CMR short-axis cine sequence images were segmented into regions of interest (ROI). Three feature subsets (ED, ES, and ED combined with ES) were established after radiomic least absolute shrinkage and selection operator feature selection. Nine radiomic models were built using random forest (RF), support vector machine (SVM), and naive Bayes. Model performance was analyzed using receiver operating characteristic curves, and metrics like accuracy, area under the curve (AUC), precision, recall, and specificity.
Results
The feature subsets included first-order, shape, and texture features. SVM of ED combined with ES achieved the highest accuracy (0.833), with a macro-average AUC of 0.941. AUCs for HHD, HWN, and NOR identification were 0.967, 0.876, and 0.963, respectively. Precisions were 0.972, 0.740, and 0.826; recalls were 0.833, 0.804, and 0.863, respectively; and specificities were 0.989, 0.863, and 0.909, respectively.
Conclusions
Radiomics technology using CMR non-enhanced cine sequences can detect early cardiac changes due to hypertension. It holds promise for future use in screening for latent cardiac damage in early HHD.
... Commonly used acquisition schemes for T1 mapping utilise Look-Locker methods and rely on inversion-recovery sequences with several single-shot acquisitions at different inversion times in stand-still diastole to achieve the most congruent position of the myocardium at each inversion time as a prerequisite for pixel-wise mapping [11][12][13] . While cardiac MRI is generally prone to artefacts due to incorrect triggering or patient movement, little is known about possible effects of conduction abnormalities, such as LBBB, on myocardial T1 measurements 14,15 . Therefore, the aim of the present study is to determine the influence of LBBB on T1 mapping 16 . ...
Tissue characterisation using T1 mapping has become an established magnetic resonance imaging (MRI) technique to detect myocardial diseases. This retrospective study aimed to determine the influence of left bundle branch block (LBBB) on T1 mapping at 1.5 T. Datasets of 36 patients with LBBB and 27 healthy controls with T1 mapping (Modified Look-Locker inversion-recovery (MOLLI), 5(3)3 sampling) were included. T1 relaxation times were determined on mid-cavity short-axis images. R² maps were generated as a pixel-wise indicator for the goodness of the fit of T1 maps. R² values were significantly lower in patients with LBBB than in healthy controls (whole myocardium/septum, 0.997, IQR, 0.00 vs. 0.998, IQR, 0.00; p = 0.008/0.998, IQR, 0.00 vs. 0.999, IQR, 0.00; p = 0.027). Manual correction of semi-automated evaluation tended to improve R² values but not significantly. Strain analysis was performed and the systolic dyssynchrony index (SDIglobal) was calculated as a measure for left ventricular dyssynchrony. While MRI is generally prone to artefacts, lower goodness of the fit in LBBB may be mainly attributable to asynchronous contraction. Therefore, careful checking of the source data and, if necessary, manual post-processing is important. New techniques might improve the goodness of the fit of T1 mapping by reducing sampling in the motion prone diastole of LBBB patients.
... As it is common to ECG gated acquisitions, excessive heart rate variability in combination with inadequate gating windows can lead to imaging in different effective cardiac phases. 54 Thus, in double ECG-gated FAIR-myoASL, this effect can lead to incongruence between the control and tag image. Due to the relatively stable duration of the systole compared to the diastole, 55 however, recent studies suggest that systolic FAIR-myoASL can offer higher robustness to such timing issues. ...
Purpose
To investigate and mitigate the influence of physiological and acquisition‐related parameters on myocardial blood flow (MBF) measurements obtained with myocardial Arterial Spin Labeling (myoASL).
Methods
A Flow‐sensitive Alternating Inversion Recovery (FAIR) myoASL sequence with bSSFP and spoiled GRE (spGRE) readout is investigated for MBF quantification. Bloch‐equation simulations and phantom experiments were performed to evaluate how variations in acquisition flip angle (FA), acquisition matrix size (AMS), heart rate (HR) and blood T1$$ {\mathrm{T}}_1 $$ relaxation time (T1,B$$ {\mathrm{T}}_{1,B} $$) affect quantification of myoASL‐MBF. In vivo myoASL‐images were acquired in nine healthy subjects. A corrected MBF quantification approach was proposed based on subject‐specific T1,B$$ {\mathrm{T}}_{1,B} $$ values and, for spGRE imaging, subtracting an additional saturation‐prepared baseline from the original baseline signal.
Results
Simulated and phantom experiments showed a strong dependence on AMS and FA (R2$$ {R}^2 $$>0.73), which was eliminated in simulations and alleviated in phantom experiments using the proposed saturation‐baseline correction in spGRE. Only a very mild HR dependence (R2$$ {R}^2 $$>0.59) was observed which was reduced when calculating MBF with individual T1,B$$ {\mathrm{T}}_{1,B} $$. For corrected spGRE, in vivo mean global spGRE‐MBF ranged from 0.54 to 2.59 mL/g/min and was in agreement with previously reported values. Compared to uncorrected spGRE, the intra‐subject variability within a measurement (0.60 mL/g/min), between measurements (0.45 mL/g/min), as well as the inter‐subject variability (1.29 mL/g/min) were improved by up to 40% and were comparable with conventional bSSFP.
Conclusion
Our results show that physiological and acquisition‐related factors can lead to spurious changes in myoASL‐MBF if not accounted for. Using individual T1,B$$ {\mathrm{T}}_{1,B} $$ and a saturation‐baseline can reduce these variations in spGRE and improve reproducibility of FAIR‐myoASL against acquisition parameters.
... These artefacts are artificial and obscure things in an image considered obstacles to a proper diagnosis. Many of these artefacts may appear in CMR images, including motion, Gibbs ringing, aliasing or wraparound, chemical-shift artefacts and those related to B0-inhomogeneities [4]. Assessing image quality subjectively in the large-scale studies like UK Biobank is a time-consuming, laborious, and non-reproducible task [5]. ...
... Previous studies [24,26] have added artefacts to CMR images by k-space manipulation techniques to generate datasets for CMR IQA. Therefore, considering that respiratory and cardiac motion, Gibbs, and aliasing artefacts are the most common artefacts in CMR images [4,27], we used the techniques introduced in our previous study [11] to add these artefacts to images and generate synthetically but realistic artefacted images. ...
... These artefacts are artificial and obscure things in an image considered obstacles to a proper diagnosis. Many of these artefacts may appear in CMR images, including motion, Gibbs ringing, aliasing or wraparound, chemical-shift artefacts and those related to B0-inhomogeneities [4]. Assessing image quality subjectively in the large-scale studies like UK Biobank is a time-consuming, laborious, and non-reproducible task [5]. ...
... Previous studies [24,26] have added artefacts to CMR images by k-space manipulation techniques to generate datasets for CMR IQA. Therefore, considering that respiratory and cardiac motion, Gibbs, and aliasing artefacts are the most common artefacts in CMR images [4,27], we used the techniques introduced in our previous study [11] to add these artefacts to images and generate synthetically but realistic artefacted images. ...
Background and Objectives: Cardiovascular magnetic resonance (CMR) imaging is a powerful modality in functional and anatomical assessment for various cardiovascular diseases. Sufficient image quality is essential to achieve proper diagnosis and treatment. A large number of medical images, the variety of imaging artefacts, and the workload of imaging centres are among the things that reveal the necessity of automatic image quality assessment (IQA). However, automated IQA requires access to bulk annotated datasets for training deep learning (DL) models. Labelling medical images is a tedious, costly and time-consuming process, which creates a fundamental challenge in proposing DL-based methods for medical applications. This study aims to present a new method for CMR IQA when there is limited access to annotated datasets. Methods: The proposed generalised deep meta-learning model can evaluate the quality by learning tasks in the prior stage and then fine-tuning the resulting model on a small labelled dataset of the desired tasks. This model was evaluated on the data of over 6,000 subjects from the UK Biobank for five defined tasks, including detecting respiratory motion, cardiac motion, Aliasing and Gibbs ringing artefacts and images without artefacts. Results: The results of extensive experiments show the superiority of the proposed model. Besides, comparing the model's accuracy with the domain adaptation model indicates a significant difference by using only 64 annotated images related to the desired tasks. Conclusion: The proposed model can identify unknown artefacts in images with acceptable accuracy, which makes it suitable for medical applications and quality assessment of large cohorts.
... Regarding phantom design, the ideal shape would have been Lorentz uniform (e.g., ellipsoid body) to avoid susceptibility-induced magnetostatic field perturbations, but such perfectly ellipsoidal geometry is difficult to mass produce. Although many phantoms are cylindrical, there are off-resonance artefacts even if the phantom is co-axially aligned with B 0 [19]. To compromise from a geometric point of view, our phantom's outer body shape along the z-axis was fairly ellipsoidal (Fig. 1i) but square in cross-section (Fig. 1ii) as it consisted of a rounded-edged, short, hollow, wide necked and leakproof brown-transparent poly vinyl chloride (PVC) bottle with a melting temperature of 140 °C. ...
Introduction:
A long T2 relaxation time can reflect oedema, and myocardial inflammation when combined with increased plasma troponin levels. Cardiovascular magnetic resonance (CMR) T2 mapping therefore has potential to provide a key diagnostic and prognostic biomarkers. However, T2 varies by scanner, software, and sequence, highlighting the need for standardization and for a quality assurance system for T2 mapping in CMR.
Aim:
To fabricate and assess a phantom dedicated to the quality assurance of T2 mapping in CMR.
Method:
A T2 mapping phantom was manufactured to contain 9 T1 and T2 (T1|T2) tubes to mimic clinically relevant native and post-contrast T2 in myocardium across the health to inflammation spectrum (i.e., 43-74 ms) and across both field strengths (1.5 and 3 T). We evaluated the phantom's structural integrity, B0 and B1 uniformity using field maps, and temperature dependence. Baseline reference T1|T2 were measured using inversion recovery gradient echo and single-echo spin echo (SE) sequences respectively, both with long repetition times (10 s). Long-term reproducibility of T1|T2 was determined by repeated T1|T2 mapping of the phantom at baseline and at 12 months.
Results:
The phantom embodies 9 internal agarose-containing T1|T2 tubes doped with nickel di-chloride (NiCl2) as the paramagnetic relaxation modifier to cover the clinically relevant spectrum of myocardial T2. The tubes are surrounded by an agarose-gel matrix which is doped with NiCl2 and packed with high-density polyethylene (HDPE) beads. All tubes at both field strengths, showed measurement errors up to ≤ 7.2 ms [< 14.7%] for estimated T2 by balanced steady-state free precession T2 mapping compared to reference SE T2 with the exception of the post-contrast tube of ultra-low T1 where the deviance was up to 16 ms [40.0%]. At 12 months, the phantom remained free of air bubbles, susceptibility, and off-resonance artifacts. The inclusion of HDPE beads effectively flattened the B0 and B1 magnetic fields in the imaged slice. Independent temperature dependency experiments over the 13-38 °C range confirmed the greater stability of shorter vs longer T1|T2 tubes. Excellent long-term (12-month) reproducibility of measured T1|T2 was demonstrated across both field strengths (all coefficients of variation < 1.38%).
Conclusion:
The T2 mapping phantom demonstrates excellent structural integrity, B0 and B1 uniformity, and reproducibility of its internal tube T1|T2 out to 1 year. This device may now be mass-produced to support the quality assurance of T2 mapping in CMR.
... Furthermore, synthetic LGE images show less motion artifacts (patient's motion, arrhythmia, etc.) than conventional LGE images, as they are based on single-shot imaging, which is less affected by motion. Also, the artifacts are further reduced by a curve-fitted imaging technique [16,17]. When we reviewed electronic medical records of five cases in which the image quality score differs the most between conventional and synthetic LGE images, four of them were due to motion artifact (e.g., breathing difficulty, poor cooperation by hearing loss, patient movement, and arrhythmia) and the other case was due to inadequate myocardial nulling time (Fig. 3). ...
Abstract Backgrounds Synthetic late gadolinium enhancement (LGE) images are less sensitive to inversion time (TI) and robust to motion artifact, because it is generated retrospectively by post-contrast T1-mapping images. To explore the clinical applicability of synthetic LGE, we investigated the image quality and diagnostic accuracy of synthetic LGE images, in comparison to that of conventional LGE for various disease groups. Method and materials From July to November 2019, a total of 98 patients who underwent cardiovascular magnetic resonance imaging (CMR), including LGE and T1-mapping sequences, with suspicion of myocardial abnormality were retrospectively included. Synthetic magnitude inversion-recovery (IR) and phase-sensitive IR (PSIR) images were generated through calculations based on the post-contrast T1-mapping sequence. Three cardiothoracic radiologists independently analyzed the image quality of conventional and synthetic LGE images on an ordinal scale with per-segment basis and the image qualities were compared with chi-square test. The agreement of LGE detection was analyzed on per-patient and per-segment basis with Cohen’s kappa test. In addition, the LGE area and percentage were semi-quantitatively analyzed for LGE positive ischemic (n = 14) and hypertrophic cardiomyopathy (n = 13) subgroups by two cardiothoracic radiologists. The difference of quantified LGE area and percentage between conventional and synthetic LGE images were assessed with Mann–Whitney U-test and the inter-reader agreement was assessed with Bland–Altman analysis. Results The image quality of synthetic images was significantly better than conventional images in both magnitude IR and PSIR through all three observers (P
... 5 With Cartesian imaging, no or poor BHs can lead to respiratory ghosting artifacts. 6 Also, inconsistencies between different BHs can result in slice misalignment, potentially leading to deviations in functional assessment. 7 Therefore, it would be of clinical interest to acquire the cine images in free-breathing (FB) while minimizing respiratory motion blurring and ghosting artifacts. ...
Purpose
To develop a free‐breathing (FB) 2D radial balanced steady‐state free precession cine cardiac MRI method with 100% respiratory gating efficiency using respiratory auto‐calibrated motion correction (RAMCO) based on a motion‐sensing camera.
Methods
The signal from a respiratory motion‐sensing camera was recorded during a FB retrospectively electrocardiogram triggered 2D radial balanced steady‐state free precession acquisition using pseudo–tiny‐golden‐angle ordering. With RAMCO, for each acquisition the respiratory signal was retrospectively auto‐calibrated by applying different linear translations, using the resulting in‐plane image sharpness as a criterium. The auto‐calibration determines the optimal magnitude of the linear translations for each of the in‐plane directions to minimize motion blurring caused by bulk respiratory motion. Additionally, motion‐weighted density compensation was applied during radial gridding to minimize through‐plane and non‐bulk motion blurring. Left ventricular functional parameters and sharpness scores of FB radial cine were compared with and without RAMCO, and additionally with conventional breath‐hold Cartesian cine on 9 volunteers.
Results
FB radial cine with RAMCO had similar sharpness scores as conventional breath‐hold Cartesian cine and the left ventricular functional parameters agreed. For FB radial cine, RAMCO reduced respiratory motion artifacts with a statistically significant difference in sharpness scores (P < 0.05) compared to reconstructions without motion correction.
Conclusion
2D radial cine imaging with RAMCO allows evaluation of left ventricular functional parameters in FB with 100% respiratory efficiency. It eliminates the need for breath‐holds, which is especially valuable for patients with no or impaired breath‐holding capacity. Validation of the proposed method on patients is warranted.
... First, the study population consisted of a small sample size and included only young healthy volunteers with normal body mass index, without any known cardiovascular disease. In the future, a larger cohort of patients with cardiovascular diseases should be included, involving subjects with arrhythmias, wall motion abnormalities, defective heart valves, and impaired BH capacity [34]. Arrhythmias could induce electrocardiographic mistriggering causing jumps in repetion time or heart-rate cycle variations which result in inconsistencies between k-space segments leading to artifacts. ...
Background:
A new 72-channel receive array coil and sensitivity encoding, compressed (C-SENSE) and noncompressed (SENSE), were investigated to decrease the number of breath-holds (BHs) for cardiac magnetic resonance (CMR).
Methods:
Three-T CMRs were performed using the 72-channel coil with SENSE-2/4/6 and C-SENSE-2/4/6 accelerated short-axis cine two-dimensional balanced steady-state free precession sequences. A 16-channel coil with SENSE-2 served as reference. Ten healthy subjects were included. BH-time was kept under 15 s. Data were compared in terms of image quality, biventricular function, number of BHs, and scan times.
Results:
BHs decreased from 7 with C-SENSE-2 (scan time 70 s, 2 slices/BH) to 3 with C-SENSE-4 (scan time 42 s, 4-5 slices/BH) and 2 with C-SENSE-6 (scan time 28 s, 7 slices/BH). Compared to reference, image sharpness was similar for SENSE-2/4/6, slightly inferior for C-SENSE-2/4/6. Blood-to-myocardium contrast was unaffected. C-SENSE-4/6 was given lower qualitative median scores, but images were considered diagnostically adequate to excellent, with C-SENSE-6 suboptimal. Biventricular end-diastolic (EDV), end-systolic (ESV) and stroke volumes, ejection fractions (EF), cardiac outputs, and left ventricle (LV)-mass were similar for SENSE-2/4/6 with no systematic bias and clinically appropriate limits of agreements. C-SENSE slightly underestimated LV-EDV (-6.38 ± 6.0 mL, p < 0.047), LV-ESV (-7.94 ± 6.0 mL, p < 0.030) and overestimated LV-EF (3.16 ± 3.10%; p < 0.047) with C-SENSE-4. Bland-Altman analyses revealed minor systematic biases in these variables with C-SENSE-2/4/6 and for LV-mass with C-SENSE-6.
Conclusions:
Using the 72-channel coil, short-axis CMR for quantifying biventricular function was feasible in two BHs where SENSE slightly outperformed C-SENSE.
... However, CMR is also prone to certain technical difficulties and pitfalls that may entail important limitations. The detailed description of CMR artefacts is beyond the scope of this review, and here we refer to source documents addressing these issues [160]. It should be noted that most clinically used CMR sequences require breath-hold and low premature ventricular beat burden during data collection as they are prone to motion artefacts. ...
... It has been long debated if we should include papillary muscles into the compact myocardium or use a simplified contouring technique excluding the papillary muscles and trabeculae [43]. Apart from significantly reducing segmentation time, emerging machine learning tools might also help standardize these contouring protocols in the future [160]. Caution should be taken during LGE characterization, too [43]. ...
Prolonged and intensive exercise induces remodeling of all four cardiac chambers, a physiological process which is coined as the “athlete’s heart”. This cardiac adaptation, however, shows overlapping features with non-ischemic cardiomyopathies, such as dilated, arrhythmogenic and hypertrophic cardiomyopathy, also associated with athlete’s sudden cardiac death. Cardiac magnetic resonance (CMR) is a well-suited, highly reproducible imaging modality that can help differentiate athlete’s heart from cardiomyopathy. CMR allows accurate characterization of the morphology and function of cardiac chambers, providing full coverage of the ventricles. Moreover, it permits an in-depth understanding of the myocardial changes through specific techniques such as mapping or late gadolinium enhancement. In this narrative review, we will focus on the certainties and uncertainties of the role of CMR in sports cardiology. The main aspects of physiological adaptation due to regular and intensive sports activity and the application of CMR in highly trained athletes will be summarized.
