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Abstract #1853

Repeatability of Diffusion Weighted Magnetic Resonance Imaging in Rectal Cancer at 1.5T.

Martijn Intven1, Onne Reerink1, Marielle E.P. Philippens1

1Radiation Oncology, UMC Utrecht, Utrecht, Netherlands

In rectal cancer, DW-MRI is increasingly used to select candidates for organ-sparing treatment after neo-adjuvant therapy. Quantitative response evaluation or prediction is based on serial DW-MRI. Assessment of the precision of ADC values is mandatory to distinguish therapy related response from measurement variations. In this study, in 14 patients, the repeatability of DW-MRI in rectal cancer was assessed at 1.5T. A repeatability coefficient for the rectal tumor of 10.0% was found for measurements in one MRI protocol, compared to 6.6% in the reference structure, the prostate central gland. Differences in ADC values of >10% can be interpreted as therapy related response in rectal cancer.