Longitudinal strain from velocity encoded cardiovascular magnetic resonance: a validation study.
BACKGROUND
Regional myocardial function is typically evaluated by visual assessment by experienced users, or by methods requiring substantial post processing time. Visual assessment is subjective and not quantitative. Therefore, the purpose of this study is to develop and validate a simple method to derive quantitative measures of regional wall function from velocity encoded cardiovascular magnetic resonance (CMR), and provide associated normal values for longitudinal strain.


METHODS
Both fast field echo (FFE) and turbo field echo (TFE) velocity encoded CMR images were acquired in three long axis planes in 36 healthy volunteers (13 women, 23 men), age 35±12 years. Strain was also quantified in 10 patients within one week after myocardial infarction. The user manually delineated myocardium in one time frame and strain was calculated as the myocardium was tracked throughout the cardiac cycle using an optimization formulation and mechanical a priori assumptions. A phantom experiment was performed to validate the method with optical tracking of deformation as an independent gold standard.


RESULTS
There was an excellent agreement between longitudinal strain measured by optical tracking and longitudinal strain measured with TFE velocity encoding. Difference between the two methods was 0.0025 ± 0.085 (ns). Mean global longitudinal strain in the 36 healthy volunteers was -0.18 ± 0.10 (TFE imaging). Intra-observer variability for all segments was 0.00 ± 0.06. Inter-observer variability was -0.02 ± 0.07 (TFE imaging). The intra-observer variability for radial strain was high limiting the applicability of radial strain. Mean longitudinal strain in patients was significantly lower (-0.15± 0.12) compared to healthy volunteers (p<0.05). Strain (expressed as percentage of normal strain) in infarcted regions was lower compared to remote areas (p<0.01).


CONCLUSIONS
In conclusion, we have developed and validated a robust and clinically applicable technique that can quantify longitudinal strain and regional myocardial wall function and present the associated normal values for longitudinal strain.
Department of Clinical Physiology, Lund University, Lund University Hospital, Lund, Sweden. einar.heiberg@med.lu.se
Einar
E
Heiberg
Ulrika
U
Pahlm-Webb
Shruti
S
Agarwal
Erik
E
Bergvall
Helen
H
Fransson
Katarina
K
Steding-Ehrenborg
Marcus
M
Carlsson
Håkan
H
Arheden
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D003287:Contrast Media; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology; D015588:Observer Variation; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D012016:Reference Values; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013997:Time Factors; D016276:Ventricular Function; D055815:Young Adult
D003287:Contrast Media