Kine Mari Bakke^{1,2}, Knut Håkon Hole^{3}, Svein Dueland^{4}, Krystyna Grøholt^{5}, Kjersti Flatmark^{6,7,8}, Anne Hansen Ree^{1,8}, Therese Seierstad^{3}, and Kathrine Røe Redalen^{1}

More accurate diagnostics for prediction of treatment responses in locally advanced rectal cancer is warranted. We employed a simplified approach to the intravoxel incoherent motion imaging method to estimate the tumour perfusion fraction from diffusion-weighted MRI. The perfusion fraction was predictive of the histologic tumour response after chemoradiotherapy (p = 0.02), and in combination with tumour volume this parameter was also predictive of five-year progression-free survival of the patients (p = 0.002). This simplified approach does not require substantial extra scan time in a routine diagnostic scanning, and may offer a clinically feasible approach to stratifying patients to individualised treatment.

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Figure 1: F was calculated as the discrepancy between the measured signal at b0
and the calculated value at b0 from an asymptotic fit from the ADC
from images b300 and b900, making a simplified approach
to the IVIM-method.

Figure 2: Sensitivity and specificity for the perfusion fraction F and tumour volume
(V). Area under curve (AUC) is indicated.

Figure 3: The combination of the perfusion fraction (F) and tumor volume (V) divided
the patients in to groups with 82% and 30% 5-year progression-free survival,
respectively.