title: Real-time 2D spatially selective MRI experiments: Comparative analysis of optimal control design methods.
abstract: There is an increasing need for development of advanced radio-frequency (RF) pulse techniques in modern magnetic resonance imaging (MRI) systems driven by recent advancements in ultra-high magnetic field systems, new parallel transmit/receive coil designs, and accessible powerful computational facilities. 2D spatially selective RF pulses are an example of advanced pulses that have many applications of clinical relevance, e.g., reduced field of view imaging, and MR spectroscopy. The 2D spatially selective RF pulses are mostly generated and optimised with numerical methods that can handle vast controls and multiple constraints. With this study we aim at demonstrating that numerical, optimal control (OC) algorithms are efficient for the design of 2D spatially selective MRI experiments, when robustness towards e.g. field inhomogeneity is in focus. We have chosen three popular OC algorithms; two which are gradient-based, concurrent methods using first- and second-order derivatives, respectively; and a third that belongs to the sequential, monotonically convergent family. We used two experimental models: a water phantom, and an in vivo human head. Taking into consideration the challenging experimental setup, our analysis suggests the use of the sequential, monotonic approach and the second-order gradient-based approach as computational speed, experimental robustness, and image quality is key. All algorithms used in this work were implemented in the MATLAB environment and are freely available to the MRI community.
authors: Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. Electronic address: ivan@e3.physik.tu-dortmund.de.
authors: Ivan I
authors: II
authors: Maximov
authors: Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, DK-8000 Aarhus, Denmark. Electronic address: msv@inano.au.dk.
authors: Mads S
authors: MS
authors: Vinding
authors: Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors: Desmond H Y
authors: DH
authors: Tse
authors: Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, DK-8000 Aarhus, Denmark.
authors: Niels Chr
authors: NC
authors: Nielsen
authors: Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; Department of Neurology, Faculty of Medicine, RWTH Aachen University, JARA, 52074 Aachen, Germany.
authors: N Jon
authors: NJ
authors: Shah
mesh_terms: D000328:Adult; D000465:Algorithms; D004574:Electromagnetic Fields; D004867:Equipment Design; D006257:Head / Q000033:anatomy & histology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D011786:Quality Control; D011846:Radio Waves; D014867:Water; D057188:Workflow
chemical_list: D014867:Water
keywords: 2D spatially selective excitation; MRI; Optimal control; RF pulse design; blOCh