Apparent Diffusion Coefficient (ADC) as a quantitative parameter in diffusion weighted MR imaging in gynecologic cancer: Dependence on b-values used
Kallehauge, J.F.; Tanderup, K.; Haack, S.ør.; Nielsen, T.; Muren, L.P.; Fokdal, L.; Lindegaard, J.C.; Pedersen, E.M.
Acta Oncologica 49(7): 1017-1022
Diffusion weighted imaging (DWI) has gained interest as an imaging modality for assessment of tumor extension and response to cancer treatment. The purpose of this study is to assess the impact of the choice of b-values on the calculation of the Apparent Diffusion Coefficient (ADC) for locally advanced gynecological cancer and to estimate a stable interval of diffusion gradients that allows for best comparison of the ADC between patients and institutions. Six patients underwent a high resolution single shot EPI based DWI scan with 16 different diffusion gradients on a 3 Tesla Philips Achieva MR-scanner. Data analysis was performed by applying a monoexponential and a biexponential model to the acquired data. The biexponential function models the effect of both perfusion and diffusion. ADC changes of up to 40% were seen with the use of different b-values. Using a lower b-value ≥ 150 s/mm(2) and an upper b-value ≥ 700 s/mm(2) limited the variation to less that 10% from the reference ADC value. By eliminating the contribution of perfusion the uncertainty of quantitative ADC values were significantly reduced.