Ventricular function assessment using MRI: comparative study between cartesian and radial techniques of k-space filling

Transcription

1 Ventricular function assessment using MRI: comparative study between cartesian and radial techniques of k-space filling Poster No.: B-0681 Congress: ECR 014 Type: Scientific Paper Authors: C. Ferreira, P. M. Martins, B. Graça, F. Peixoto, S. Monteiro, S. Barbosa, M. Castelo-Branco ; Coimbra/PT, Aveiro/PT Keywords: Cardiac, MR, Technical aspects, Education DOI: /ecr014/B-0681 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 9

2 Purpose Cartesian K-space trajectories are routinely used in cardiac MRI studies to evaluate ventricular function [1,]. However, due to relatively long acquisition times, required long breath-hold times and are prone to movement/respiratory artefacts [1-3]. Radial k-space filling allows an acquisition less prone to movement/respiratory artefacts but is prone to blurring and sticking artefacts that could affect image quality [-5]. The aim of this study is to assess overall image quality and compare cardiac measures derived from two kspace sampling techniques (cartesian and radial) in the evaluation of ventricular function. Methods and materials Subjects Ten young adults aged 4,10 ± 3,414 (5 female and 5 male) without cardiac pathology where enrolled in this study.before their enrolment they were informed about the objectives of the study and their informed consent was obtained. A MR safety screening was also performed to ensure that all the volunteers had all the safety requisites to be submitted safely to the scanner. MRI Protocol The Cardiac cine images were collected at IBILI and acquired with a 3 Tesla scanner. A standard 16-channel body and a spine matrix coil were used. Two and four chamber localizers and a short axis localizer were initially acquired to program cine sequences. Short axis cine images were acquired in EEG retrospective gating and in breath-hold. The sequences were acquired with the parameters as described in Table 1. Image Processing and Statistical Analysis Quantitative analysis for the evaluation of left ventricular function was performed using Siemens Argus function to calculate ejection fraction (EF), diastolic volume (EDV) and systolic volume (ESV). Left ventricular segmentation was done based on the short axis cine images by semi-automatic delimitation, being as criterions the delineation of endocardium cavity and epicardiac lines (manual adjustments were made (Figure 1)). Page of 9

3 Statistical analysis was performed with IBM SPSS Statistics, version , 64bit edition. The differences in the assessment of LV (Left Ventricle) volumes and EF between both k-sampling techniques were tested using the Student's paired t-test (pvalue 0,05) after verifying normality with Shapiro-Wilk tests. The imaging techniques were qualitatively assessed by an experienced radiologist on a four-point scale (4-excellent, 1-non-diagnostic). A Wilcoxon test was performed to evaluate differences between the scores attributed to images obtained using the two techniques. Images for this section: Table 1: Parameters used to acquire MRI Cardiac Images. Page 3 of 9

4 Fig. 1: Delineation lines to estimate the parameters for functional evaluation (ESV, EDV, EJ). Red - endocardium delineation line; Green - epicardiac delineation line. Page 4 of 9

5 Results The radial technique yielded images with fewer artefacts than the cartesian technique, with overall good delineation of the endocardium (Figure ). The median scores attributed by the experienced radiologist to the images were and 3 for cartesian k-space filling and for the radial k-space filling, respectively. The qualitative difference between the images is statistically significant, as assessed by the Wilcoxon test (p=0.034). Concerning the quantitative analysis, EDV was ±4.9mL for the radial technique and 13.30±4.15mL for the cartesian technique (p=0.18). The corresponding EF values were 69.63±4.09% and 68.56±5.17% (p=0.31). ESV was 41.70± 9,45mL for the radial technique and for the Cartesian technique 41,90± (Table and 3). In order to better visualise and understand the differences between the two k-space techniques, a box plot was built (Figure 3). There are no visible outliers and only slight differences between the two k-space filling techniques. The slight differences observed were statistically evaluated and both k-space filling techniques show a similar behaviour as shown in Table 4 (all differences non-significant). Images for this section: Page 5 of 9

6 Fig. : a) an example of cartesian k-space filling short axis acquisition; b) radial k-space filling short axis acquisition. Note more movement artefact in a) as compared with b). Table : Results of the calculated values using cartesian k-space filling. Table 3: Results of the calculated values using radial k-space filling. Fig. 3: Box plot for the calculated values of the evaluated cardiac function parameters. a) 1 - EDV Cartesian technique; - ESV Cartesian technique Cine; 3 - EDV Radial technique; 4 - ESV Radial Technique. b) 5- EF Cartesian technique and 6 - EF Radial technique. Page 6 of 9

7 Table 4: Comparisons of mean results. Page 7 of 9

8 Conclusion Despite some limitations due to the presence of artefacts which are more conspicuous at higher fields [6-8], cardiac MRI has several advantages in comparison with other imaging methods. Ventricular function assessment is feasible with the use of radial kspace sampling with better overall image quality in comparison with cartesian technique. The latter is more prone to respiratory artefacts. Despite the relatively low sample size, this study suggests that radial k-sampling holds promise in the evaluation of patients with difficulties performing breath-hold techniques. Personal information Carlos Ferreira, Institute of Biomedical Research in Light and Imaging, Faculty of Medicine, University of Coimbra / Institute of Nuclear Sciences Applied to Health, University of Coimbra / Superior School of Health, University of Aveiro, Portugal. Paula Martins, Superior School of Health/Institute of Electronics and Telematics Engineering of the University of Aveiro, Portugal. Bruno Graça (MD), Radiology Sector - Radiology Department of Coimbra University Hospital (CHUC) Filipa Peixoto, Superior School of Health, University of Aveiro, Portugal. Samuel Monteiro, Superior School of Health, University of Aveiro, Portugal. Sérgio Barbosa, Superior School of Health, University of Aveiro, Portugal. Miguel Castelo-Branco (MD; PhD), Institute of Biomedical Research in Light and Imaging, Faculty of Medicine, University of Coimbra, Portugal. References [1] Kaji, S., Yang, P. C., Kerr, A. B., Tang, W. H. W., Meyer, C. H., Macovski, A., Pauly, J. M., Nishimura, D. G., Hu, B. S. (001). Rapid evaluation of left ventricular volume Page 8 of 9

9 and mass without breath-holding using real- time interactive cardiac magnetic resonance imaging system. Journal of the American College of Cardiology, 38 (): [] Xie, J., Lai, P., Huang, F., Li, Y., Li, D. (010). Cardiac magnetic resonance imaging using radial k-space sampling and self-calibrated partial parallel reconstruction. Magn Reson Imaging, 8 (4): [3] Muthurangu, V., Lurz, P., Critchely, J.D., Deanfield, J.E., Taylor, A.M., Hansen, M.S. (008). Real-time assessment of right and left ventricular volumes and functions in patients with congenital heart disease by using high spatiotemporal resolution radial kt SENSE. Radiology, 48 (3): [4] Jahnke, C., Paetsch, I., Schnackenburg, B., Gebker, R., Kohler, U., Bornstedt, A., Fleck, E., Nagel, E. (004). Comparison of radial and Cartesian imaging techniques for MR coronary angiography. J Cardiovasc Magn Reson, 6 (4): [5] Shankaranarayanan, A., Simonetti, O. P., Laub, G., Lewin, J. S., Duerk, J. L. (001). Segmented k-space and Real-Time Cardiac Cine MR Imaging with Radial Trajectories1. Radiology, 1(3): [6] Nayak, K.S, Cunningham, C.H, Santos, J.M., Pauly, J.M. (004). Real-time cardiac MRI at 3 Tesla. Magnetic Resonance in Medicine 51: [7] Smith, T.B., Nayak, K.S. (010). MRI artifacts and correction strategies. Imaging Med. (4): [8] Ferreira, P.F, Gatehouse, P.D., Mohiaddin, R.H., Firmin, D.N. (013). Cardiovascular magnetic resonance artefacts. Journal of Cardiovascular Magnetic Resonance, 15 (41). Page 9 of 9