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Optimizing IMPULSED Acquisition Protocols for Clinical 3T Scanners Through Bayesian Experimental Design
Yan Dai1, Xun Jia2, Todd Aguilera1
1Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Purpose:
To optimize diffusion MRI acquisition protocols for Imaging Microstructural Parameters Using Limited Spectrally Edited Diffusion (IMPULSED) model at clinical 3T scanner using Bayesian experimental design, enabling accurate cellular-scale parameter estimation under realistic scan time and scanner hardware constraints.
Methods:
Expected Information Gain (EIG) was used as the optimization objective to maximize the information content of acquired measurements for IMPULSED model fitting. Bayesian optimization with Gaussian process surrogates efficiently searched the high-dimensional acquisition parameter space, including pulse types (PGSE, OGSEn1, and OGSEn2), diffusion times, and b values. Optimized protocols were systematically evaluated against a heuristically designed baseline protocol through simulation studies assessing classification accuracy and parameter estimation performance across SNR levels of 5-40. Robustness to optimization assumptions was examined by varying prior distributions and assumed SNR. In vivo validation was performed using canine tumor data acquired at 3T.
Results:
The optimized protocol eliminated OGSEn2 acquisitions, concentrated measurements at high b values (maximum 2000 s/mm2 for PGSE, 1220 s/mm2 for OGSEn1), employing concurrently optimized diffusion timing. Compared to the baseline protocol, the optimized design achieved superior classification accuracy for distinguishing cell populations and reduced parameter estimation error across biologically relevant parameter ranges at various SNRs. Performance advantages were consistent across diverse optimization scenarios, demonstrating robustness to prior knowledge and noise assumptions. In vivo parameter maps showed substantially improved quality and smoothness.
Conclusion:
Bayesian optimization substantially improves IMPULSED acquisition design for clinical 3T scanners. This principled, algorithm-agnostic framework enables accurate diffusion MRI cytometry under clinical constraints, with potential applications to tumor characterization and treatment monitoring.
