Improved Pediatric MR Imaging with Compressed Sensing

Abstract

Purpose:To develop a method that combines parallel imaging and compressed sensing to enable faster and/or higher spatial resolution magnetic resonance (MR) imaging and show its feasibility in a pediatric clinical setting. Materials and Methods:Institutional review board approval was obtained for this HIPAA-compliant study, and informed consent or assent was given by subjects. A pseudorandom k-space undersampling pattern was incorporated into a threedimensional (3D) gradient-echo sequence; aliasing then has an incoherent noiselike pattern rather than the usual coherent fold-over wrapping pattern. This k-space-sampling pattern was combined with a compressed sensing nonlinear reconstruction method that exploits the assumption of sparsity of medical images to permit reconstruction from undersampled k-space data and remove the noiselike aliasing. Thirty-four patients (15 female and 19 male patients; mean age, 8.1 years; range, 0-17 years) referred for cardiovascular, abdominal, and knee MR imaging were scanned with this 3D gradient-echo sequence at high acceleration factors. Obtained k-space data were reconstructed with both a traditional parallel imaging algorithm and the nonlinear method. Both sets of images were rated for image quality, radiologist preference, and delineation of specifi c structures by two radiologists. Wilcoxon and symmetry tests were performed to test the hypothesis that there was no signifi cant difference in ratings for image quality, preference, and delineation of specifi c structures. Results:Compressed sensing images were preferred more often, had signifi cantly higher image quality ratings, and greater delineation of anatomic structures ( P , .001) than did images obtained with the traditional parallel reconstruction method. Conclusion:A combination of parallel imaging and compressed sensing is feasible in a clinical setting and may provide higher resolution and/or faster imaging, addressing the challenge of delineating anatomic structures in pediatric MR imaging.q RSNA, 2010

Compressed sensing MRI: a review of the clinical literature

“…32 A total of 275 subjects were imaged across the 18 studies (range, 3-34; mean 5 15.28; median 5 11.5; standard deviation 5 10.23). 7 studies imaged healthy subjects, 15,[19][20][21]23,24,27 and 11 imaged patients referred for the type of imaging under consideration 1,2,14,[16][17][18]22,25,26,28,29 ( Figure 5). …”

“…22 In 10 studies human readers rated images. 1,15,18,[21][22][23][26][27][28][29] In eight studies, accurate measurement of a quantitative metric with CS MRI (e.g. contrast uptake or metabolite concentration) was assessed.…”

“…MR images are thus susceptible to motion-related artefacts, which may even necessitate sedation or anaesthesia. Relatively low temporal resolution limits MRI of body parts that move with respiration, such as in abdominal 1 and cardiac imaging. 2 Long scan times increase costs and limit the number of patients for whom MRI is available.…”

“…10 However, PI acceleration factors .2 are not reliably achievable in the clinic, without unacceptable image degradation. 1 Within the past decade, another technique has been developed and has been applied to accelerate MRI acquisition.…”

“…However, publications are largely focused on technical aspects of methodology and implementation; few studies 1,2,14229 have examined the quality and diagnostic efficacy of accelerated CS images (Figure 1b). This review evaluates the literature assessing performance of CS for clinical applications, where diagnostic efficacy is of the utmost importance.…”