Influence of orientation, size and shape of the region of interest in diffusion MRI along perivascular spaces index

• Published in: Magma (New York, N.Y.) Vol. 38; no. 5; pp. 761 - 769
• Main Authors: Ulloa, Patricia, Rudolf, Justus Christian, Kremer, Janina, Schmidt, Aileen, Schramm, Peter
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.10.2025; Springer Nature B.V
• Subjects: Adult; Agreements; Algorithms; Basic Science - Diffusion; Biomedical Engineering and Bioengineering; Brain - diagnostic imaging; Brain cancer; Cerebrospinal fluid; Computer Appl. in Life Sciences; Configurations; Diffusion; Diffusion Magnetic Resonance Imaging - methods; Diffusion Tensor Imaging - methods; Female; Glymphatic System - diagnostic imaging; Health Informatics; Healthy Volunteers; Humans; Hypotheses; Image Processing, Computer-Assisted - methods; Imaging; Imaging techniques; Male; Mathematical analysis; Medicine; Medicine & Public Health; Middle Aged; Parameter sensitivity; Radiology; Reliability; Reproducibility of Results; Research Article; Solid State Physics; Statistical analysis; Tensors; Young Adult; United States > US; Germany; Interstitial fluid dynamics; Glymphatic system; ROI standardization; ALPS method; DWI ALPS; Neurofluids; DTI ALPS; Harmonization
• ISSN: 1352-8661; 0968-5243; 1352-8661
• DOI: 10.1007/s10334-025-01248-0

Objective Diffusion-tensor imaging (DTI) and diffusion-weighted imaging (DWI) along perivascular spaces (ALPS) index have been proposed as noninvasive techniques to indirectly evaluate the glymphatic system function. However, these techniques are sensitive to examination parameters, limiting inter-study comparability. The definition of the region of interest (ROI) has been identified as the primary weakness of the ALPS method. Therefore, we aimed to determine which ROI characteristics would best promote consistent ALPS index analysis. Methods We examined 13 healthy volunteers using DTI and DWI to calculate the ALPS index, and compared and determined correlations among 11 different ROI configurations, and tested inter-method reliability. Results We found significant differences between different ROI configurations in the ALPS index calculation. Considering ROI characteristics and inter-method reliability, a squared ROI is the most suitable. The ICC between ROI configurations showed good-to-excellent inter-method agreement (mean ICC = 0.83). We did not find significant inter-method differences. Conclusion It is important to standardize the ROI characteristics for consistent ALPS index calculation.