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Normal Brain and Brain Tumor ADC: Changes Resulting From Variation of Diffusion Time and/or Echo Time in
Jens Johansson1, Kerstin Lagerstrand, Isabella M Björkman-Burtscher
1From the Department of Radiology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden (J.J., I.M.B.-B., M.L., H.H., S.E.M.); Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden (K.L.); Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Region Västra Götaland, Gothenburg, Sweden (J.J., K.L.); Department of Radiology, Sahlgrenska University Hospital, Region Västra Götaland, Gothenburg, Sweden (I.M.B.-B., M.L., H.H.); and Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (S.E.M.).
Apparent diffusion coefficient (ADC) measurements in brain tumors are sensitive to pulsed-gradient spin echo (PGSE) sequence timing. Tumor ADC values can change significantly with echo time and gradient performance, impacting diagnostic accuracy.
Area of Science:
- Neuroimaging
- Biomedical Engineering
- Radiology
Background:
- Modern MRI scanners offer faster imaging but reduce attainable diffusion and echo times for pulsed-gradient spin echo (PGSE) sequences.
- Apparent diffusion coefficient (ADC) is a key biomarker for differentiating brain tissue and monitoring treatment.
- Investigating the impact of sequence parameters on ADC is crucial for accurate clinical interpretation.
Purpose of the Study:
- To evaluate the dependence of ADC on diffusion time and echo time in brain MRI.
- To assess the influence of gradient performance on ADC measurements.
- To determine the clinical relevance of these ADC variations in healthy tissues and brain tumors.
Main Methods:
- Diffusion time and echo time dependence of ADC were assessed using PGSE sequences on a 3 T MRI scanner.
- Scans were performed in 10 healthy volunteers and 10 brain tumor patients with varying diffusion times (16-70 ms) and echo times (60-104 ms).
- Gradient performance was varied, and ADC was measured in gray matter, white matter, and solid tumor regions.
Main Results:
- Normal brain tissue showed minimal ADC changes (<2.6%) with varying diffusion and echo times.
- Brain tumors exhibited significant ADC variations (up to 12% with echo time, up to 21% with reduced gradient performance).
- Tumor ADC changes were dependent on diffusivity and sequence parameters, unlike normal tissue.
Conclusions:
- Normal tissue ADC changes are negligible within the studied PGSE parameter range.
- Tumor ADC measurements are sensitive to timing parameters, potentially affecting quantitative biomarker utility.
- Standardized reporting of timing parameters and protocol optimization are essential for multicenter ADC studies.
