Theoretical Considerations on Joint Inference of Cardiac Diffusion and Strain Tensors from second-order motion compensated cDTI Data

Abstract

Cardiac diffusion tensor imaging (cDTI) as well as cardiac strain imaging both offer invaluable information on the functional state of the heart. Acquiring both, takes too long to be clinically feasible. Free breathing, cDTI acquisition with second-order motion compensated diffusion encoding waveforms display residual phase variations, that encode higher orders of contractile motion during the diffusion encoding process. This work presents a theoretical framework on how to jointly infer strain and diffusion tensors from complex-valued cDTI data with varying trigger delays.

CMRsim–A python package for cardiovascular MR simulations incorporating complex motion and flow

“…64,65 Sequence definitions for the experiments described in this work were based on CMRseq. 51 In conclusion, CMRsim is a simulation framework that allows the incorporation of complex motion to systematically study advanced CMR acquisition and reconstruction approaches. The open-source package features modularity and transparency, facilitating maintainability and extensibility in support of reproducible research.…”

“…CMRsim deliberately does not contain functionality to define MR sequences, as this functionality is not inherent to the simulation logic and therefore should be implemented separately, such as using (Py)Pulseq 64,65 . Sequence definitions for the experiments described in this work were based on CMRseq 51 …”

“…Figure 3 shows a flowchart of the simulation experiment. The NumPy arrays defining gradient and RF waveforms, as well as sampling events, were generated using the CMRseq 51 package. In addition to the unweighted reference, six velocity encodings (VENCs) were used: (550, 50, 250, 50, 100, 50) cm/s in directions ([0, 0, 1], [0, 0, 1], [0, 1, 0], [0, 1, 0], [1, 0, 0], [1, 0, 0]).…”

“…The experiment described in this section aims to study the effect of cardiac motion–induced phase on cardiac diffusion tensor estimation when using acceleration‐compensated diffusion encoding with spin echoes (SE‐M012) 54 . The SE‐M012 single‐shot EPI sequence, including binomial excitation pulses, was defined using CMRseq 51 . The temporal grid for RF and gradient waveforms was set to 100 μs.…”

“…54 The SE-M012 single-shot EPI sequence, including binomial excitation pulses, was defined using CMRseq. 51 The temporal grid for RF and gradient waveforms was set to 100 μs. The EPI readout was defined using a 91 × 49 matrix and an in-plane resolution of 2 × 2 mm.…”