Diffusion-weighted MR imaging including bi-exponential fitting for the detection of recurrent or residual tumour after (chemo)radiotherapy for laryngeal and hypopharyngeal cancers

Objectives To assess whether diffusion-weighted magnetic resonance imaging (DW-MRI) including bi-exponential fitting helps to detect residual/recurrent tumours after (chemo)radiotherapy of laryngeal and hypopharyngeal carcinoma. Methods Forty-six patients with newly-developed/worsening symptoms after (chemo)radiotherapy for laryngeal/hypopharyngeal cancers were prospectively imaged using conventional MRI and axial DW-MRI. Qualitative (visual assessment) and quantitative analysis (mono-exponentially: total apparent diffusion coefficient [ADC T ], and bi-exponentially: perfusion fraction [F P ] and true diffusion coefficient [ADC D ]) were performed. Diffusion parameters of tumour versus post-therapeutic changes were compared, with final diagnosis based on histopathology and follow-up. Mann-Whitney U test was used for statistical analysis. Results Qualitative DW-MRI combined with morphological images allowed the detection of tumour with a sensitivity of 94% and specificity 100%. ADC T and ADC D values were lower in tumour with values 120 ± 49 × 10 −5 mm 2 /s and 113 ± 50 × 10 −5 mm 2 /s, respectively, compared with post-therapeutic changes with values 182 ± 41 × 10 −5 mm 2 /s ( P