4D Flow CMR data were analyzed with in-house developed software based on Matlab (Version R2012a, Mathworks Inc., Novi, MI). First, the LV endocardial boundaries were manually delineated using MASS research software (Version 2013EXP, Leiden University Medical Center, Leiden, The Netherlands). Subsequently, the Lambda2-method was applied to the 4D Flow CMR data to identify the vortex structures within the LV blood pool. Early (E) filling and atrial (A) filling phases were defined from the flow rate-time graph after transmitral velocity mapping in combination with retrospective valve tracking . For every subject, the vortex ring core (if detected) of peak early filling and peak late filling was used for further quantitative analysis. As described in previous work, the Lambda2 isovalue threshold ( Tλ2) was defined as Tλ2=Kμ (with K as a real number and μ as the λ2 average of voxels with λ2 < 0) with K chosen as the value providing the most circular vortex ring core having the least attached trailing structures . The parameter K was chosen separately for every filling phase. The shape and location of the peak early (E) and late (A) -vortex ring cores were further quantitatively analyzed using the parameters explained below. In the remainder, the vortex cores detected at peak early filling and peak late filling will be denoted as E-vortex and A-vortex, respectively.
Tudo isso com uma taxa de quadros inferior a 16 quadros por segundo?
Estudar a diástole requer taxas de quadro superiores, preferencialmente acima de 30.
Em outro momento sugere uma captura de 35 quadros por segundo.