Current artefacts in cardiac and chest magnetic resonance imaging: tips and tricks

Abstract

Currently MRI is extensively used for the evaluation of cardiovascular and thoracic disorders because of the well-established advantages that include use of non-ionizing radiation, good contrast and high spatial resolution. Despite the advantages of this technique, numerous categories of artefacts are frequently encountered. They may be related to the scanner hardware or software functionalities, environmental factors or the human body itself. In particular, some artefacts may be exacerbated with high-field-strength MR machines (e.g. 3 T). Cardiac imaging poses specific challenges with respect to breath-holding and cardiac motion. In addition, new cardiac MR-conditional devices may also be responsible for peculiar artefacts. The image quality may thus be impaired and give rise to a misdiagnosis. Knowledge of acquisition and reconstruction techniques is required to understand and recognize the nature of these artefacts. This article will focus on the origin and appearance of the most common artefacts encountered in cardiac and chest MRI along with possible correcting methods to avoid or reduce them.

Figure 1.

Zipper artefacts present as lines of electronic noise extending perpendicular to the frequency-encoding direction throughout the image series. A defective light was the cause. Another aspect is a sharp spike at the centre of the image.

Figure 2.

An aliasing or wrap-around artefact occurs because the imaged chest is larger than the field of view (FOV). It results in the projection of the right arm located beyond FOV boundaries on the left hemithorax.

Figure 3.

Late gadolinium enhancement images in the short-axis direction, showing two small fibrotic areas (arrows). (a) A large wrap-round artefact (asterisk) overlays the heart owing to reproduction of the anatomical structure outside the field of view in the phase-encoding direction. (b) The wrap-round artefact is placed outside the heart by changing the phase-encoding direction, resulting in a better quality and diagnostic image.

Figure 4.

Zebra artefacts appear as alternating curved bright and dark bands mainly at the periphery of the MR image (a). The inhomogeneity of the magnetic field combined with aliasing may also give rise to a centrally located artefact (b).

Figure 5.

A round magnetic susceptibility artefact observed in a volumetric interpolated breath-hold sequence with gadolinium injection (a) that was not seen on a balanced steady-state free precession sequence (b). This artefact is projected on an underlying pleural effusion with alveolar consolidation of the right lower lobe.

Figure 6.

Magnetic susceptibility artefacts noticed during a balanced steady-state free precession sequence at 3 T, simulating an aortic dissection at the level of the aortic arch (a) (thick arrow). A pseudoflap appearance located in the descending aorta was also seen in another patient referred for cardiac MRI (b) (thin arrow). In (b), the artefactual nature was easily recognized owing to the same appearance in the pulmonary trunk (hollow arrow).

Figure 7.

Cine images at end-diastole in short-axis view at the mid-ventricular level using balanced steady-state free precession (a) and fast spoiled gradient echo (b) in a patient with an implantable cardioverter defibrillator. In (a), large dark band off-resonance and generator-related ferromagnetic susceptibility (arrow) artefacts hamper the image interpretation. In (b), dark band off-resonance artefacts are not any longer present and only the generator-related ferromagnetic susceptibility artefact is visible (arrow), resulting in good image quality adequate for clinical interpretation. The use of cine fast-spoiled gradient echo has the advantage of not being associated with dark band off-resonance artefacts.

Figure 8.

A 50-year-old male with congenital heart disease who underwent pulmonary valve replacement with biological valve prosthesis. Metallic artefacts related to sternotomy (arrows) are associated with total signal dropout on volumetric interpolated breath-hold sequence (a), but they are not any longer visualized on the half-Fourier acquisition single-shot turbo spin-echo sequence (b). Metallic artefacts may also appear as peripheral high signal intensity (arrowheads) (c).

Figure 9.

Dixon artefacts most commonly related to a local swapping of water and fat signal which generates complementary geographic areas of signal void (asterisks). (a, c) Water images and (b, d) fat images.

Figure 10.

Dixon artefacts simulating pulmonary embolism visible on the water (a) and fat images (b) (arrows). The artefact disappeared in the opposition sequence (c). Although the quadrangular shape was suggestive of an artefact, CT pulmonary angiography (d) performed to definitely exclude this diagnosis was normal.

Figure 11.

A truncation artefact appearing as central low signal intensity within the right laterobasal pulmonary artery (arrow) on contrast-enhanced pulmonary MR angiography (a). Such artefacts appear parallel to the abrupt transitions between regions of high and low signal intensities as in the case of opacified vessels. This was misdiagnosed as pulmonary embolism that was excluded by CT angiogram (b) performed following the MR examination. Note the dilated oesophagus in this patient with gastric bypass (asterisks).

Figure 12.

Motion artefacts related to breathing.

Figure 13.

Ghost artefacts on the volumetric interpolated breath-hold examination sequence due to non-electrocardiogram, triggering generating alternative white and black curved lines parallel to the border of the ascending aorta (solid arrow) (a), right cardiac border (white arrows with black border) (b) and ascending aorta (open arrow) (c).

Figure 14.

A ghost artefact of the ascending aorta (arrows) in the sagittal oblique plane (a) that should not be confused with a real chronic dissection of the descending aorta as seen in sagittal and axial planes (b) in this 44-year-old male with Marfan syndrome.

Figure 15.

Cardiac ghost artefacts on the volumetric interpolated breath-hold examination sequence more prominent in the phase-encoding direction projecting posteriorly on the lung parenchyma (open arrow) (a). This should not be confused with the abnormal signal more laterally located in the left lower lobe on a half-Fourier acquisition single-shot turbo spin-echo sequence (solid arrow) (b). The latter signal corresponded to a ground-glass nodule on CT (c) metabolically hyperactive on positron emission tomography (d) that was related to pulmonary localization of a primary gastric lymphoma (arrows).

Figure 16.

End-diastolic (a) and end-systolic (b) cine images in the horizontal long-axis view using retrospective electrocardiogram gating in a patient with frequent ectopic ventricular beats. Using cross-validation-sparse (compressed sensing), the cine images are acquired in a single breath-hold heart beat, resulting in a significant improvement of image quality at end-diastole (c) and end-systole (d). The compressed sensing applies a compression algorithm during the acquisition process and then reconstructs the undersampled data with a novel non-linear reconstruction algorithm.

Figure 17.

End-diastolic (a) and end-systolic (b) cine images in a patient with atrial fibrillation (irregular R–R interval) using retrospective electrocardiogram (ECG) gating. With this method, the images are acquired continuously throughout the cardiac cycle over several (irregular) heart beats. Using prospective ECG triggering, the acquisition window is limited to the systolic phase (in this case, 350 ms after R-wave), partially avoiding the artefacts due to irregular R–R interval. This approach results in a better image quality at end-diastole (c) and end-systole (d) and throughout the imaged cardiac cycle.

Figure 18.

Flow artefacts generating a signal loss in the pulmonary trunk and the left main pulmonary artery on the axial image of the volumetric interpolated breath-hold sequence (a) disappearing on the sagittal oblique image (b) and coronal views (c).

Figure 19.

Flow artefacts observed in the half-Fourier acquisition single-shot turbo spin-echo sequence simulating aortic dissection (a) and pulmonary embolism (c) that disappeared on volumetric interpolated breath-hold examination sequences (b, d). These artefacts are mainly related to the axial orientation of the aortic arch and left main pulmonary artery when performing dark-blood double inversion-recovery pulse sequence. A perpendicular black-blood sequence to these vessels could also suppress these artefacts.

Figure 20.

Abnormal signal in the interlobar artery on half-Fourier acquisition single-shot turbo spin echo (a) confirmed as pulmonary embolism on axial (b), sagittal (c) and coronal volumetric interpolated breath-hold examination sequences (d). For each abnormal signal intensity seen on one plane or sequence, its presence should always be confirmed on other planes and sequences.