Myocardial T1 mapping using SMART1Map: initial in vivo experience
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KeywordsHeart Rate Variability Heart Beat Heart Rate Variation Cardiac Interval Single Shot Image
Recently a single-point, saturation-recovery myocardial T1 mapping sequence (SMART1Map = Saturation Method using Adaptive Recovery Times for cardiac T1 Mapping) was presented . Compared to common methods like MOLLI, SMART1Map measures true T1 instead of apparent T1 relaxation, is more time efficient and can track exact TI times instead of estimated ones based on the heart rate during prescription. In this work we compare SMART1Map to MOLLI in an initial cohort of volunteers.
Versions of SMART1Map and MOLLI were implemented on a GE MR450w scanner. Four healthy subjects were imaged without contrast agent and with informed consent. Single shot images were acquired at the TI times. SMART1Map acquisitions collected 5 TIs in 9 heart beats at 1,1,1,2 and 4 heart beats after saturation. MOLLI acquisitions collected 8 TIs (2,2 and 4 heartbeats after each inversion) in 14 heart beats. A total of 12 data sets for each sequence were collected. T1 values in an ROI in the mid-septum were calculated. Values were computed with both estimated TI times based on the heart rate at the time of scan prescription and true TI times based on pulse sequence measurements of each cardiac interval during scanning. MOLLI values were computed with and without Look-Locker (LL) correction . SMART1Map values represent true, not apparent, T1 values and thus no correction was applied.
Mean measured T1 values in normal myocardium.
Mean T1 values (N=12)
MOLLI no LL correction
MOLLI with LL correction and estimated TI times
MOLLI with LL correction and measured TI times
SMART1Map with estimated TI times
SMART1Map with measured (true) TI times
SMART1Map is a new T1 mapping method that provides accurate, breath held, true myocardial T1 values for normal myocardium. Compared to literature values, it provides more accurate T1 measurements compared to MOLLI which studies have shown underestimates long T1s.
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