T<sub>2</sub>-adjusted computed diffusion-weighted imaging: A novel method to enhance tumour visualisation.
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<h4>Purpose</h4>To introduce T<sub>2</sub>-adjusted computed DWI (T<sub>2</sub>-cDWI), a method that provides synthetic images at arbitrary b-values and echo times (TEs) that improve tissue contrast by removing or increasing T<sub>2</sub> contrast in diffusion-weighted images.<h4>Materials and methods</h4>In addition to the standard DWI acquisition protocol T<sub>2</sub>-weighted echo-planar images at multiple (≥2) echo times were acquired. This allows voxelwise estimation of apparent diffusion coefficient (ADC) and T<sub>2</sub> values, permitting synthetic images to be generated at any chosen b-value and echo time. An analytical model is derived for the noise properties in T<sub>2</sub>-cDWI, and validated using a diffusion test-object. Furthermore, we present T<sub>2</sub>-cDWI in two example clinical case studies: (i) a patient with mesothelioma demonstrating multiple disease tissue compartments and (ii) a patient with primary ovarian cancer demonstrating solid and cystic disease compartments.<h4>Results</h4>Measured image noise in T<sub>2</sub>-cDWI from phantom experiments conformed to the analytical model and demonstrated that T<sub>2</sub>-cDWI at high computed b-value/TE combinations achieves lower noise compared with conventional DWI. In patients, T<sub>2</sub>-cDWI with low b-value and long TE enhanced fluid signal while suppressing solid tumour components. Conversely, large b-values and short TEs overcome T<sub>2</sub> shine-through effects and increase the contrast between tumour and fluid compared with conventional high-b-value DW images.<h4>Conclusion</h4>T<sub>2</sub>-cDWI is a promising clinical tool for improving image signal-to-noise, image contrast, and tumour detection through suppression of T<sub>2</sub> shine-through effects.
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Diffusion Magnetic Resonance Imaging
Image Processing, Computer-Assisted
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Computers in biology and medicine, 2016, 79 pp. 92 - 98