Optimizing cardiac diffusion tensor imaging in vivo: More directions or repetitions?.

Coveney, S.; Shelley, D.; Foster, RJ.; Afzali, M.; Poenar, AM.; Sharrack, N.; Plein, S.; Dall'Armellina, E.; Schneider, JE.; Nguyen, C.; Teh, I.

Optimizing cardiac diffusion tensor imaging in vivo: More directions or repetitions?.

All Authors

Coveney, S.

Shelley, D.

Foster, RJ.

Afzali, M.

Poenar, AM.

Sharrack, N.

Plein, S.

Dall'Armellina, E.

Schneider, JE.

Nguyen, C.

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LTHT Author

Shelley, David

LTHT Department

Radiology

Non Medic

Research Radiographer

Publication Date

2025

Item Type

Journal Article
Comparative Study

Abstract

BACKGROUND: Cardiac diffusion tensor imaging (cDTI) is sensitive to imaging parameters, including the number of unique diffusion encoding directions (ND) and number of repetitions (NR; analogous to number of signal averages). However, there is no clear guidance for optimizing these parameters in the clinical setting. METHODS: Spin echo cDTI data with second-order motion-compensated diffusion encoding gradients were acquired in 10 healthy volunteers on a 3T magnetic resonance imaging scanner with different diffusion encoding schemes in pseudo-randomized order. The data were subsampled to yield 96 acquisition schemes with 6 <= ND <= 30 and 33 <= total number of acquisitions (NAall) <= 180. Stratified bootstrapping with robust fitting was performed to assess the accuracy and precision of each acquisition scheme. This was quantified across a mid-ventricular short-axis slice in terms of root mean squared difference (RMSD), with respect to the full reference dataset, and standard deviation (SD) across bootstrap samples, respectively. RESULTS: For the same acquisition time, the ND = 30 schemes had on average 48%, 40%, 34%, and 34% lower RMSD and 6.2%, 7.4%, 10%, and 5.6% lower SD in mean diffusivity (MD), fractional anisotropy (FA), helix angle (HA), and absolute sheetlet angle ( E2A ) compared to the ND = 6 schemes. Given a fixed number of high b-value acquisitions, there was a trend toward lower RMSD and SD of MD and FA with increasing numbers of low b-value acquisitions. Higher NAall with longer acquisition times led to improved accuracy in all metrics, whereby quadrupling NAall from 40 to 160 volumes led to a 20%, 39%, 11%, and 5.4% reduction in RMSD of MD, FA, HA, and E2A , respectively, averaged across six diffusion encoding schemes. Precision was also improved with a corresponding 53%, 50%, 53%, and 36% reduction in SD. CONCLUSION: We observed that accuracy and precision were enhanced by (i) prioritizing number of diffusion encoding directions over NR given a fixed acquisition time, (ii) acquiring sufficient low b-value data, and (iii) using longer protocols where feasible. For clinically relevant protocols, our findings support the use of ND = 30 and NAb50:NAb500 >= 1/3 for better accuracy and precision in cDTI parameters. These findings are intended to help guide protocol optimization for harmonization of cDTI.