Long term safety and visibility of a novel liquid fiducial marker for use in image guided radiotherapy of non-small cell lung cancer by Blanck, D, Rydhög, J, Larsen, K, Clementsen, P, Josipovic, M, Aznar, M, Af Rosenschöld, P, Jølck, R, Specht, L, Andresen, T, Persson, G