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Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging
Published on: November 8, 2012
Reproducibility of spatial penalty-based methodologies for intravoxel incoherent motion analysis with diffusion MRI
Esha Baidya Kayal1, Shuvadeep Ganguly2, Devasenathipathy Kandasamy3
1Centre for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, India.
Abstract:
Objective was to assess the precision and reproducibility of spatial penalty-based intravoxel incoherent motion (IVIM) methods in comparison to the conventional bi-exponential (BE) model-based IVIM methods. IVIM-MRI (11 b-values; 0-800 s/mm2) of forty patients (N = 40; Age = 17.7 ± 5.9 years; Male:Female = 30:10) with biopsy-proven osteosarcoma were acquired on a 1.5 Tesla scanner at 3 time-points: (i) baseline, (ii) after 1-cycle and (iii) after 3-cycles of neoadjuvant chemotherapy. Diffusion coefficient (D), Perfusion coefficient (D*) and Perfusion fraction (f) were estimated at three time-points in whole tumor and healthy muscle tissue using five methodologies (1) BE with three-parameter-fitting (BE), (2) Segmented-BE with two-parameter-fitting (BESeg-2), (3) Segmented-BE with one-parameter-fitting (BESeg-1), (4) BE with adaptive Total-Variation-penalty (BE + TV) and (5) BE with adaptive Huber-penalty (BE + HPF). Within-subject coefficient-of-variation (wCV) and between-subject coefficient-of-variation (bCV) of IVIM parameters were measured in healthy and tumor tissue. For precision and reproducibility, intra-scan comparison of wCV and bCV among five IVIM methods were performed using Friedman test followed by Wilcoxon-signed-ranks (WSR) post-hoc test. Experimental results demonstrated that BE + TV and BE + HPF showed significantly (p < 10-3) lower wCV and bCV for D (wCV: 24-32%; bCV: 22-31%) than BE method (wCV: 38-49%; bCV: 36-46%) across three time-points in healthy muscle and tumor. BE + TV and BE + HPF also demonstrated significantly (p < 10-3) lower wCV and bCV for estimating D* (wCV: 89-108%; bCV: 83-102%) and f (wCV: 55-60%; bCV: 56-60%) than BE, BESeg-2 and BESeg-1 methods (D*-wCV: 102-122%; D*-bCV: 98-114% and f-wCV: 96-130%; f-bCV: 94-125%) in both tumor and healthy tissue across three time-points. Spatial penalty based IVIM analysis methods BE + TV and BE + HPF demonstrated lower variability and improved precision and reproducibility in the current clinical settings.
Insights
Spatial penalty-based intravoxel incoherent motion (IVIM) methods, specifically BE+TV and BE+HPF, offer improved precision and reproducibility for diffusion coefficient (D), perfusion coefficient (D*), and perfusion fraction (f) in osteosarcoma patients compared to conventional models.
Area of Science:
- Medical Imaging
- Radiology
- Oncology
Background:
- Intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) is a valuable technique for assessing tissue microenvironment.
- Conventional bi-exponential (BE) IVIM models face challenges in precision and reproducibility, particularly in dynamic studies like chemotherapy response assessment.
- Spatial penalty-based methods offer potential improvements in IVIM parameter estimation.
Purpose of the Study:
- To compare the precision and reproducibility of spatial penalty-based IVIM methods (BE+TV, BE+HPF) against conventional BE models.
- To evaluate IVIM parameter estimation (D, D*, f) in osteosarcoma patients undergoing neoadjuvant chemotherapy.
- To determine the efficacy of different IVIM fitting methodologies in clinical settings.
Main Methods:
- IVIM MRI was performed on 40 osteosarcoma patients at baseline, after 1 cycle, and after 3 cycles of chemotherapy using 11 b-values (0-800 s/mm²).
- Diffusion coefficient (D), perfusion coefficient (D*), and perfusion fraction (f) were estimated using five methods: BE, BESeg-2, BESeg-1, BE+TV, and BE+HPF.
- Within-subject (wCV) and between-subject (bCV) coefficients of variation were calculated for healthy muscle and tumor tissues to assess precision and reproducibility.
Main Results:
- BE+TV and BE+HPF methods demonstrated significantly lower wCV and bCV for D, D*, and f compared to conventional BE, BESeg-2, and BESeg-1 methods (p < 10⁻³).
- These improvements in precision and reproducibility were observed across all three time-points in both healthy muscle and tumor tissues.
- Spatial penalty-based methods showed substantially reduced variability in IVIM parameter estimation.
Conclusions:
- Spatial penalty-based IVIM analysis methods (BE+TV and BE+HPF) offer superior precision and reproducibility over conventional methods.
- These advanced IVIM techniques are well-suited for clinical applications, including monitoring treatment response in osteosarcoma.
- The improved reliability of BE+TV and BE+HPF enhances their utility in quantitative MRI studies.
