title: On the R2⁎relaxometry in complex multi-peak multi-Echo chemical shift-based water-fat quantification: Applications to the neuromuscular diseases.
abstract: Investigation of the feasibility of the R2⁎mapping techniques by using latest theoretical models corrected for confounding factors and optimized for signal to noise ratio.
  
  
  
  The improvement of the performance of state of the art magnetic resonance imaging (MRI) relaxometry algorithms is challenging because of a non-negligible bias and still unresolved numerical instabilities. Here, R2⁎mapping reconstructions, including complex fitting with multi-spectral fat-correction by using single-decay and double-decay formulation, are deeply studied in order to investigate and identify optimal configuration parameters and minimize the occurrence of numerical artifacts. The effects of echo number, echo spacing, and fat/water relaxation model type are evaluated through both simulated and in-vivo data. We also explore the stability and feasibility of the fat/water relaxation model by analyzing the impact of high percentage of fat infiltrations and local transverse relaxation differences among biological species.
  
  
  
  The main limits of the MRI relaxometry are the presence of bias and the occurrence of artifacts, which significantly affect its accuracy. Chemical-shift complex R2⁎-correct single-decay reconstructions exhibit a large bias in presence of a significant difference in the relaxation rates of fat and water and with fat concentration larger than 30%. We find that for fat-dominated tissues or in patients affected by extensive iron deposition, MRI reconstructions accounting for multi-exponential relaxation time provide accurate R2⁎measurements and are less prone to numerical artifacts.
  
  
  
  Complex fitting and fat-correction with multi-exponential decay formulation outperforms the conventional single-decay approximation in various diagnostic scenarios. Although it still lacks of numerical stability, which requires model enhancement and support from spectroscopy, it offers promising perspectives for the development of relaxometry as a reliable tool to improve tissue characterization and monitoring of neuromuscular disorders.
authors: Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University of Messina, V.le F. D'alcontres, 31, 98166, Messina, Italy; Department of Computer Engineering and Telecommunications, University of Catania, Viale Andrea Doria 6, 95125, Catania, Italy. Electronic address: giuliosiracusano@gmail.com.
authors: Giulio
authors: G
authors: Siracusano
authors: Department of Computer Engineering and Telecommunications, University of Catania, Viale Andrea Doria 6, 95125, Catania, Italy.
authors: Aurelio
authors: A
authors: La Corte
authors: Department of Biomedical sciences, Dental and of Morphological and Functional images, University of Messina, Via Consolare Valeria 1, 98125, Messina, Italy.
authors: Carmelo
authors: C
authors: Milazzo
authors: Department of Biomedical sciences, Dental and of Morphological and Functional images, University of Messina, Via Consolare Valeria 1, 98125, Messina, Italy.
authors: Giuseppe Pio
authors: GP
authors: Anastasi
authors: Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University of Messina, V.le F. D'alcontres, 31, 98166, Messina, Italy; Istituto Nazionale di Geofisica e Vulcanologia (INGV), Via Vigna Murata 605, 00143, Roma, Italy.
authors: Giovanni
authors: G
authors: Finocchio
authors: Department of Biomedical sciences, Dental and of Morphological and Functional images, University of Messina, Via Consolare Valeria 1, 98125, Messina, Italy.
authors: Michele
authors: M
authors: Gaeta
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000473:pathology; D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008962:Models, Theoretical; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000473:pathology; D009468:Neuromuscular Diseases / Q000000981:diagnostic imaging*; D059629:Signal-To-Noise Ratio; D014867:Water
chemical_list: D014867:Water
keywords: Chemical shift; Fat-water; Multi Echo; Neuromuscular disease; R(2)(⁎) relaxometry; TRID