Ultrasound elastography and diffusion weighted MRI in patients with rectal cancer

OBJECTIVE: The current literature has described the usefulness of elastography and diffusion weighted MRI in cancer patients, but to the best of our knowledge so far none of them have compared the two new methods. The tumour cell density is related to the MRI measured apparent diffusion weighted coefficient (ADC). The purpose of the present study was to compare quantitative elastography based on ultrasound shear wave measurements with MRI ADC. METHODS AND MATERIALS: We prospectively examined consecutive 52 patients with histopathological proven rectal cancer. The tumour elasticity was measured using the Acoustic Radiation Force Impulse (ARFI) to generate information on the mechanical properties of the tissue. The objective quantitative elastography shear wave velocity was blindly compared to the ADC measurements using a 1.5 Tesla MRI system. The study was approved by the local Clinical Ethics Committee. RESULTS: The mean tumour elasticity was 3.05 m/s (SD:0.79) and the mean ADC was 0.69 mm2/s (SD: 0.27). Elasticity was inversely strong correlated with ADC, r = -0.65 (Salkin scale). ARFI = 4.392 – 1.949 x ADC, R2 = 0.43, P < 000.1. Intercept = 4.392 (95% CI:3.92 – 4.86), Slope = -1.949 (95% CI: -1.31 - -2.59), P < 0.0001. CONCLUSION: Elasticity correlates with the estimated diffusion restriction by MRI ADC measurements in rectal tumours. The relationship between ARFI and ADC measurement was linear in our study population.