Quantitative dynamic contrast enhanced MRI of recurrent pelvic masses in patients treated for cancer

Recurrent tumour and post-treatment inflammatory masses may be difficult to differentiate on T2 weighted and post-contrast T1 weighted MR sequences. The purpose of this study was to assess the value of quantitative analysis of enhancement patterns in improving the separation of tumour recurrence from benign post-treatment masses in the pelvis. 32 patients with a total of 44 benign or malignant pelvic masses arising more than 6 months after treatment by surgery and/or radiotherapy were studied. After localizing the lesion on T1 and T2 weighted sequences, sequential T1 weighted spoiled gradient recalled echo (SPGR) images were obtained through the mass during bolus intravenous injection of 0.1 mmol kg-1 of Gd-chelate. Analysis of the maximum enhancement and proportion of maximum enhancement by 30, 60 and 90 s after onset of injection was performed prospectively by radiologists using standard manufacturer's software. Semi-automated analyses using software to provide irregular regions of interest and automated signal intensity measurements were also performed. Maximum enhancement was significantly greater in tumour recurrence than fibrosis following surgery, with better separation between the two groups using computer assisted analysis (p <0.001) than manual analysis (p <0.05). Separation between post-radiotherapy tumour recurrence and benign post-radiotherapy masses reached statistical significance for manual measurements of maximum enhancement (p <0.05) but not for computer assisted analysis. There was no significant difference in enhancement rates between benign and malignant masses in post-radiotherapy patients. Measurement of the maximum enhancement of a mass alone does not reliably separate lesions in the post-radiotherapy patient but may be helpful when considered together with signal intensity and morphology on conventional MRI sequences.