T₂-adjusted computed diffusion-weighted imaging: A novel method to enhance tumour visualisation

Purpose: To introduce T₂-adjusted computed DWI (T₂-cDWI), a method that provides synthetic images at arbitrary b-values and echo times (TEs) that improve tissue contrast by removing or increasing T₂ contrast in diffusion-weighted images.

Materials and methods: In addition to the standard DWI acquisition protocol T₂-weighted echo-planar images at multiple (≥2) echo times were acquired. This allows voxelwise estimation of apparent diffusion coefficient (ADC) and T₂ 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 T₂-cDWI, and validated using a diffusion test-object. Furthermore, we present T₂-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.

Results: Measured image noise in T₂-cDWI from phantom experiments conformed to the analytical model and demonstrated that T₂-cDWI at high computed b-value/TE combinations achieves lower noise compared with conventional DWI. In patients, T₂-cDWI with low b-value and long TE enhanced fluid signal while suppressing solid tumour components. Conversely, large b-values and short TEs overcome T₂ shine-through effects and increase the contrast between tumour and fluid compared with conventional high-b-value DW images.

Conclusion: T₂-cDWI is a promising clinical tool for improving image signal-to-noise, image contrast, and tumour detection through suppression of T₂ shine-through effects.