Can we predict the diffusion "sweet-spot" based on a standard cine?

Background Cardiac diffusion tensor imaging (cDTI) is often performed using a stimulated echo sequence with monopolar diffusion encoding [1,2]. While diffusion measured with this sequence is modified by strain [1] the standard strain model predicts that the strain effects can be eliminated by imaging at one of two “sweet-spots” in the cardiac cycle where the effects of strain cancel [3]. However, analysis of strain data to calculate the sweetspot timings (SST) is typically too time consuming to be performed during an exam. Here we hypothesise that the SST is linearly related to the time to peak strain (PST) and PST will be approximately equal to end-systole time (EST) estimated from a standard cine. If so, EST could be used to easily predict SST. Methods 2D spiral cine DENSE data [4] from a mid-ventricular short axis slice in 13 healthy subjects was analysed using the DENSE analysis tool from the University of Virginia [5]. Data were acquired on a Siemens Skyra with either a 3D (navigator gated, 0.10 cycles/mm balanced encoding, n = 5) or a 2D encoded protocol (breath hold, 0.06 cycles/m simple encoding), both 30 ms temporal/3.5 × 3.5 × 8 mm spatial resolution. Global radial and circumferential strain curves were analysed. The SST were defined as the time points during systolic contraction and diastolic relaxation where the strain was closest to the mean strain over the cardiac cycle. Radial and circumferential PST were averaged. EST was estimated as the timing of the image with minimum left ventricular