A system for assessing a pulmonary image and for determining a radiation dose level, the system comprising: - a pulmonary image providing unit configured to provide a pulmonary image which comprises image elements to which image values are assigned and which shows lung vessels, - a smoothing unit configured to smooth the provided pulmonary image for providing different pulmonary images with different degrees of smoothing, - a signal value determination unit configured to determine signal values for the different pulmonary images (20, 21, 22), wherein for a respective pulmonary image several signal values, which are indicative of the detectability of the lung vessels in the respective pulmonary image, are determined based on the image values of the respective pulmonary image, - a noise value determination unit configured to determine noise values for the different pulmonary images (20, 21, 22), wherein for a respective pulmonary image several noise values, which are indicative of the noise in the respective pulmonary image, are determined based on the image values of the respective pulmonary image, - an image quality determination unit configured to determine an image quality for the provided unsmoothed image based on the signal values and noise values determined for the different pulmonary images (20, 21, 22), wherein the system further comprises a dose level determination unit configured to determine the radiation dose level to be applied for generating a next pulmonary image based on the determined image quality, and wherein the signal value determination unit is adapted to determine the signal values for different sizes of the lung vessels in the different pulmonary images, wherein the noise value determination unit is adapted to determine the noise values for the different sizes of the lung vessels in the different pulmonary images, and wherein the image quality determination unit is configured to provide reference signal values and reference noise values for different sizes of lung vessels and to determine the image quality such that it is indicative of a deviation of a) the determined signal values and the determined noise values from b) the provided reference signal values and reference noise values. - a pulmonary image providing unit configured to provide a pulmonary image which comprises image elements to which image values are assigned and which shows lung vessels, - a smoothing unit configured to smooth the provided pulmonary image for providing different pulmonary images with different degrees of smoothing, - a signal value determination unit configured to determine signal values for the different pulmonary images (20, 21, 22), wherein for a respective pulmonary image several signal values, which are indicative of the detectability of the lung vessels in the respective pulmonary image, are determined based on the image values of the respective pulmonary image, - a noise value determination unit configured to determine noise values for the different pulmonary images (20, 21, 22), wherein for a respective pulmonary image several noise values, which are indicative of the noise in the respective pulmonary image, are determined based on the image values of the respective pulmonary image, - an image quality determination unit configured to determine an image quality for the provided unsmoothed image based on the signal values and noise values determined for the different pulmonary images (20, 21, 22), wherein the system further comprises a dose level determination unit configured to determine the radiation dose level to be applied for generating a next pulmonary image based on the determined image quality, and