title: Systolic ShMOLLI myocardial T1-mapping for improved robustness to partial-volume effects and applications in tachyarrhythmias.
abstract: BACKGROUND
  T1-mapping using the Shortened Modified Look-Locker Inversion Recovery (ShMOLLI) technique enables non-invasive assessment of important myocardial tissue characteristics. However, tachyarrhythmia may cause mistriggering and inaccurate T1 estimation. We set out to test whether systolic T1-mapping might overcome this, and whether T1 values or data quality would be significantly different compared to conventional diastolic T1-mapping.
  
  
  METHODS
  Native T1 maps were acquired using ShMOLLI at 1.5 T (Magnetom Avanto, Siemens Healthcare) in 10 healthy volunteers (5 male) in sinus rhythm, at varying prescribed trigger delay (TD) times: 0, 50, 100 and 150 ms (all "systolic"), 340 ms (MOLLI TD 500 ms, the conventional TD for ShMOLLI) and also "end diastolic". T1 maps were also acquired using a shorter readout, to explore the effect of reducing image readout time and sensitivity to systolic motion. The feasibility and image quality of systolic T1-mapping was tested in 15 patients with tachyarrhythmia (n = 13 atrial fibrillation, n = 2 sinus tachycardia; mean HR range 93-121 bpm).
  
  
  RESULTS
  In healthy volunteers, systolic readout increased the thickness of myocardium compared to the diastolic readout. There was a small overall effect of TD on T1 values (p = 0.04), with slightly shorter T1 values in systole compared to diastole (maximum difference 10 ms). While there were apparent gender differences (with no effect of TD on T1 values in males, more marked differences in females, and exaggeration of this effect in thinner myocardial segments in females), dilatation and erosion of contours suggested that the effect of TD on T1 in females was almost entirely due to more partial-volume effects in diastole. All T1 maps were of excellent quality, but systolic TD and shorter readout were associated with less variability in segmental T1 values. In tachycardic patients, systolic acquisitions produced consistently excellent T1 maps (median R (2) = 0.993).
  
  
  CONCLUSIONS
  In healthy volunteers, systolic ShMOLLI T1-mapping reduces T1 variability and reports clinically equivalent T1 values to conventional diastolic readout; slightly shorter T1 values in systole are mostly explained by reduced partial-volume effects due to the increase in functional myocardial thickness. In patients with tachyarrhythmia, systolic ShMOLLI T1-mapping is feasible, circumvents mistriggering and produces excellent quality T1 maps. This extends its clinical applicability to challenging rhythms (such as rapid atrial fibrillation) and aids the investigation of thinner myocardial segments. With further validation, systolic T1-mapping may become a new and convenient standard for myocardial T1-mapping.
authors: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU, Oxford, UK. vanessa.ferreira@cardiov.ox.ac.uk.
authors: Vanessa M
authors: VM
authors: Ferreira
authors: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU, Oxford, UK. rohan.wijesurendra@cardiov.ox.ac.uk.
authors: Rohan S
authors: RS
authors: Wijesurendra
authors: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU, Oxford, UK. alexander.liu@cardiov.ox.ac.uk.
authors: Alexander
authors: A
authors: Liu
authors: Siemens Healthcare, Erlangen, Germany. andreas.greiser@siemens.com.
authors: Andreas
authors: A
authors: Greiser
authors: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU, Oxford, UK. barbara.casadei@cardiov.ox.ac.uk.
authors: Barbara
authors: B
authors: Casadei
authors: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU, Oxford, UK. matthew.robson@cardiov.ox.ac.uk.
authors: Matthew D
authors: MD
authors: Robson
authors: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU, Oxford, UK. stefan.neubauer@cardiov.ox.ac.uk.
authors: Stefan
authors: S
authors: Neubauer
authors: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU, Oxford, UK. s_k_piechnik@yahoo.co.uk.
authors: Stefan K
authors: SK
authors: Piechnik
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology*; D005240:Feasibility Studies; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006331:Heart Diseases / Q000473:pathology* / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009206:Myocardium / Q000473:pathology*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012737:Sex Factors; D013599:Systole; D013616:Tachycardia, Sinus / Q000175:diagnosis / Q000503:physiopathology*; D013997:Time Factors