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Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging
Published on: November 8, 2012
Repeatability of derived parameters from histograms following non-Gaussian diffusion modelling of diffusion-weighted
Neil P Jerome1, Keiko Miyazaki1, David J Collins1
1Division of Radiotherapy & Imaging, The Institute of Cancer Research, Cancer Research UK Cancer Imaging Centre, 123 Old Brompton Road, London, SW7 3RP, UK.
Insights
Repeatability of diffusion imaging parameters in pediatric solid tumors was assessed. The stretched exponential model showed good repeatability, while perfusion and kurtosis parameters exhibited high variability, suggesting caution in their interpretation.
Area of Science:
- Medical Imaging
- Radiology
- Pediatric Oncology
Background:
- Diffusion-weighted imaging (DWI) provides insights into tissue microstructure.
- Non-Gaussian diffusion models offer advanced analysis beyond simple diffusion coefficients.
- Assessing the repeatability of these advanced models is crucial for clinical application in pediatric oncology.
Purpose of the Study:
- To evaluate the repeatability of parameters derived from intravoxel incoherent motion (IVIM), stretched exponential, and kurtosis diffusion models.
- To determine the reliability of these parameters across different histogram centiles in pediatric solid tumors.
Main Methods:
- 17 pediatric patients (<16 years) with solid tumors underwent repeat DWI scans (1.5 T, 6 b-values) 24 hours apart.
- Tumor regions of interest (ROIs) were analyzed using IVIM, stretched exponential, and kurtosis models.
- Percentage coefficients of variation (CV) were calculated for model parameters across histogram centiles.
Main Results:
- Apparent diffusion coefficient (ADC), D, DDCα, α, and DDcK showed CV <10% down to the 5th centile.
- K, f, and D* parameters exhibited high CV (>30%) across the histogram.
- ADC, D, DDCα, and DDcK were highly correlated (ρ > 0.9).
Conclusions:
- The stretched exponential model demonstrated good repeatability for DDCα and α parameters.
- Perfusion and kurtosis parameters showed significant variability, necessitating cautious interpretation.
- ADC, D, DDCα, and DDcK are repeatable metrics, especially at the median and down to the 5th centile.
Objectives:
To examine repeatability of parameters derived from non-Gaussian diffusion models in data acquired in children with solid tumours.
Methods:
Paediatric patients (<16 years, n = 17) were scanned twice, 24 h apart, using DWI (6 b-values, 0-1000 mm-2 s) at 1.5 T in a prospective study. Tumour ROIs were drawn (3 slices) and all data fitted using IVIM, stretched exponential, and kurtosis models; percentage coefficients of variation (CV) calculated for each parameter at all ROI histogram centiles, including the medians.
Results:
The values for ADC, D, DDCα, α, and DDCK gave CV < 10 % down to the 5th centile, with sharp CV increases below 5th and above 95th centile. K, f, and D* showed increased CV (>30 %) over the histogram. ADC, D, DDCα, and DDCK were strongly correlated (ρ > 0.9), DDCα and α were not correlated (ρ = 0.083).
Conclusion:
Perfusion- and kurtosis-related parameters displayed larger, more variable CV across the histogram, indicating observed clinical changes outside of D/DDC in these models should be interpreted with caution. Centiles below 5th for all parameters show high CV and are unreliable as diffusion metrics. The stretched exponential model behaved well for both DDCα and α, making it a strong candidate for modelling multiple-b-value diffusion imaging data.
Key Points:
• ADC has good repeatability as low 5th centile of the histogram distribution. • High CV was observed for all parameters at extremes of histogram. • Parameters from the stretched exponential model showed low coefficients of variation. • The median ADC, D, DDC α , and DDC K are highly correlated and repeatable. • Perfusion/kurtosis parameters showed high CV variations across their histogram distributions.
