An optimized b ‐value sampling for the quantification of interstitial fluid using diffusion‐weighted MRI , a genetic algorithm approach

• Published in: Magnetic resonance in medicine Vol. 90; no. 1; pp. 194 - 201
• Main Authors: Drenthen, Gerhard S., Jansen, Jacobus F. A., van der Thiel, Merel M., Voorter, Paulien H. M., Backes, Walter H.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.07.2023
• Subjects: Algorithms; Brain - diagnostic imaging; Computer Simulation; Diffusion; Diffusion Magnetic Resonance Imaging - methods; Estimation; Extracellular Fluid - diagnostic imaging; Genetic algorithms; Magnetic resonance imaging; Mathematical models; Microvasculature; Parenchyma; Root-mean-square errors; Sampling; interstitial fluid; glymphatics; magnetic resonance imaging; IVIM; diffusion weighted imaging; cerebral clearance
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.29612

Multi-b-value diffusion-weighted MRI techniques can simultaneously measure the parenchymal diffusivity, microvascular perfusion, and a third, intermediate diffusion component. This component is related to the interstitial fluid in the brain parenchyma. However, simultaneously estimating three diffusion components from multi-b-value data is difficult and has strong dependence on SNR and chosen b-values. As the number of acquired b-values is limited due to scanning time, it is important to know which b-values are most effective to be included. Therefore, this study evaluates an optimized b-value sampling for interstitial fluid estimation. The optimized b-value sampling scheme is determined using a genetic algorithm. Subsequently, the performance of this optimized sampling is assessed by comparing it with a linear, logarithmic, and previously proposed sampling scheme, in terms of the RMS error (RMSE) for the intermediate component estimation. The in vivo performance of the optimized sampling is assessed using 7T data with 101 equally spaced b-values ranging from 0 to 1000 s/mm . In this case, the RMSE was determined by comparing the fit that includes all b-values. The optimized b-value sampling for estimating the intermediate component was reported to be [0, 30, 90, 210, 280, 350, 580, 620, 660, 680, 720, 760, 980, 990, 1000] s/mm . For computer simulations, the optimized sampling had a lower RMSE, compared with the other samplings for varying levels of SNR. For the in vivo data, the voxel-wise RMSE of the optimized sampling was lower compared with other sampling schemes. The genetic algorithm-optimized b-value scheme improves the quantification of the diffusion component related to interstitial fluid in terms of a lower RMSE.