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Background: In cardiac magnetic resonance imaging (MRI), left ventricular stroke volume (SV) and ejection fractions (EF) are occasionally calculated using single-plane and biplane ellipsoid models. In previous studies, the calculated SV and EF using single- and biplane ellipsoid models have been compared to reference values calculated from short-axis (SA) images. In these studies, however, it has been emphasized that through-plane motion of the basal SA images represents an important source of error, which may result in incorrect reference values. Purpose: To compare the calculated SV and EF using single-plane and biplane ellipsoid models with SV and EF calculated from SA images in which compensation was made for through-plane motion. Material and Methods: A group of 20 patients who underwent MRI examination were included in the study. SV and EF were calculated using the stack of SA images (which had been compensated for through-plane motion) and compared to the SV and EF calculated according to the single- and biplane ellipsoid models. Results: The mean difference between the single-plane model and the reference was -0.3±6.5 for EF and 7.2±17.1 ml for SV. Corresponding comparison between the biplane method and the reference resulted in a mean difference of 0.3±6.1 for EF and 11.8±14.9 ml for SV. Conclusion: The results from this study show that left ventricular EF can be adequately estimated using the single- and biplane ellipsoid models, while SV tends to be overestimated using both geometrical models. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to evaluate commercial metal artefact reduction (MAR) techniques in X-ray CT imaging of hip prostheses. Methods: Monoenergetic reconstructions of dual-energy CT (DECT) data and several different MAR algorithms, combined with single-energy CT or DECT, were evaluated by imaging a bilateral hip prosthesis phantom. The MAR images were compared with uncorrected images based on CT number accuracy and noise in different regions of interest. Results: The three MAR algorithms studied implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to the prostheses and between the two prostheses, The application of monoenergetic reconstruction, without any MAR algorithm, did not decrease the noise in the regions close to the prostheses to the same extent as did the MAR algorithms and even increased the noise in the region between the prostheses. Conclusion: The MAR algorithms evaluated generally improved CT number accuracy and substantially reduced the noise in the hip prostheses phantom images, both close to the prostheses and between the two prostheses. The study showed that the monoenergetic reconstructions evaluated did not sufficiently reduce the severe metal artefact caused by large orthopaedic implants. Advances in knowledge: This study evaluates several commercially available MAR techniques in CT imaging of large orthopaedic implants. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance (MR) imaging and echocardiography both allow assessment of aortic valve stenosis. In MR the aortic valve area (AvA) is measured using planimetry while in transthoracic echocardiography (TTE) AvA is usually calculated by applying the continuity equation. Purpose: To compare the measured stenotic aortic valve areas using five different MR-acquisition alternatives with the corresponding area values calculated by TTE. Material and Methods: The aortic valve was imaged in 14 patients, with diagnosed aortic valve stenosis, using balanced steady state free precession (bSSFP) gradient echo (GE) and phase contrast imaging (PC). Three adjacent slices were planned to encompass the aortic valve and the aortic valve area was measured using planimetry. The two sets of complex valued images generated by the PC sequence formed three kinds of images that could be used for aortic valve area measurements: the magnitude image (PC/Mag), the modulus (PCA/M), and phase difference (PCA/P) between the two complex images, respectively. The valve area from TTE was calculated using the continuity equation. A cut-off of <1.0 cm(2) was used as a criteria for severe stenosis. Results: The mean area differences between the different MR acquisitions and TTE method were -0.05 ± 0.37 cm(2) (GE), -0.18 ± 0.46 cm(2) (bSSFP), 0.27 ± 0.43 cm(2) (PC/Mag), 0.15 ± 0.32 cm(2) (PCA/P), and 0.26 ± 0.27 cm(2) (PCA/M). The valve area was significantly overestimated using PCA/M that, in turn, implied a significant underestimation of the aortic valve stenosis severity compared to the assessments using TTE. Conclusion: The smallest area valve difference between TTE and an MR-acquisition alternative is obtained with gradient echo images. The use of PCA/M leads to significant differences in planimetry measurements of the aortic valve orifice and the gradation of the stenosis severity compared to TTE. [ABSTRACT FROM AUTHOR]