title: T2 mapping of the heart with a double-inversion radial fast spin-echo method with indirect echo compensation.
abstract: BACKGROUND
  The abnormal signal intensity in cardiac T2-weighted images is associated with various pathologies including myocardial edema. However, the assessment of pathologies based on signal intensity is affected by the acquisition parameters and the sensitivities of the receiver coils. T2 mapping has been proposed to overcome limitations of T2-weighted imaging, but most methods are limited in spatial and/or temporal resolution. Here we present and evaluate a double inversion recovery radial fast spin-echo (DIR-RADFSE) technique that yields data with high spatiotemporal resolution for cardiac T2 mapping.
  
  
  METHODS
  DIR-RADFSE data were collected at 1.5 T on phantoms and subjects with echo train length (ETL) = 16, receiver bandwidth (BW) = ±32 kHz, TR = 1RR, matrix size = 256 × 256. Since only 16 views per echo time (TE) are collected, two algorithms designed to reconstruct highly undersampled radial data were used to generate images for 16 time points: the Echo-Sharing (ES) and the CUrve Reconstruction via pca-based Linearization with Indirect Echo compensation (CURLIE) algorithm. T2 maps were generated via least-squares fitting or the Slice-resolved Extended Phase Graph (SEPG) model fitting. The CURLIE-SEPG algorithm accounts for the effect of indirect echoes. The algorithms were compared based on reproducibility, using Bland-Altman analysis on data from 7 healthy volunteers, and T2 accuracy (against a single-echo spin-echo technique) using phantoms.
  
  
  RESULTS
  Both reconstruction algorithms generated in vivo images with high spatiotemporal resolution and showed good reproducibility. Mean T2 difference between repeated measures and the coefficient of repeatability were 0.58 ms and 2.97 for ES and 0.09 ms and 4.85 for CURLIE-SEPG. In vivo T2 estimates from ES were higher than those from CURLIE-SEPG. In phantoms, CURLIE-SEPG yielded more accurate T2s compared to reference values (error was 7.5-13.9% for ES and 0.6-2.1% for CURLIE-SEPG), consistent with the fact that CURLIE-SEPG compensates for the effects of indirect echoes. The potential of T2 mapping with CURLIE-SEPG is demonstrated in two subjects with known heart disease. Elevated T2 values were observed in areas of suspected pathology.
  
  
  CONCLUSIONS
  DIR-RADFSE yielded TE images with high spatiotemporal resolution. Two algorithms for generating T2 maps from highly undersampled data were evaluated in terms of accuracy and reproducibility. Results showed that CURLIE-SEPG yields T2 estimates that are reproducible and more accurate than ES.
authors.affiliation: Biomedical Engineering Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona, USA. tbarr@email.arizona.edu.
authors.forename: Tomoe
authors.initials: T
authors.lastname: Hagio
authors.affiliation: Department of Mathematics, University of Arizona, Tucson, Arizona, USA. chuan.huang@stonybrook.edu.|Departments of Radiology and Psychiatry, Stony Brook University, Stony Brook, New York, USA. chuan.huang@stonybrook.edu.
authors.forename: Chuan
authors.initials: C
authors.lastname: Huang
authors.affiliation: Department of Medicine, University of Arizona, Tucson, Arizona, USA. aabidov@shc.arizona.edu.|Arizona Sarver Heart Center, University of Arizona, Tucson, Arizona, USA. aabidov@shc.arizona.edu.
authors.forename: Aiden
authors.initials: A
authors.lastname: Abidov
authors.affiliation: Department of Medicine, University of Arizona, Tucson, Arizona, USA. drjaspreet28@gmail.com.
authors.forename: Jaspreet
authors.initials: J
authors.lastname: Singh
authors.affiliation: Department of Medicine, University of Arizona, Tucson, Arizona, USA. bujji.dr@gmail.com.
authors.forename: Bujji
authors.initials: B
authors.lastname: Ainapurapu
authors.affiliation: Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA. ssquire@email.arizona.edu.
authors.forename: Scott
authors.initials: S
authors.lastname: Squire
authors.affiliation: Arizona Sarver Heart Center, University of Arizona, Tucson, Arizona, USA. dbruck@shc.arizona.edu.
authors.forename: Denise
authors.initials: D
authors.lastname: Bruck
authors.affiliation: Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA. maltbach@email.arizona.edu.
authors.forename: Maria I
authors.initials: MI
authors.lastname: Altbach
mesh_terms: D000465:Algorithms; D006331:Heart Diseases / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016018:Least-Squares Analysis; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D009206:Myocardium / Q000473:pathology*; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D015203:Reproducibility of Results