An apparatus for segmenting an object comprising sub-objects shown in an object image, the apparatus comprising: - a feature image generation unit for generating a feature image showing features related to intermediate regions between the sub-objects from the object image, wherein the feature image generation unit comprises a feature enhancing unit for enhancing features related to intermediate regions between the sub-objects in the object image, - a segmentation unit for segmenting the sub-objects by using the object image and the feature image, wherein the segmentation unit comprises: - a model providing unit for providing a model object comprising model sub-objects (13, 14, 15, 16, 17), - a pre-positioning unit for pre-positioning the model object in the object image and the feature image, and - an adaptation unit for adapting the model object to the object in the object image and in the feature image, wherein the adaptation unit is adapted such that a surface of a model sub-object facing another model sub-object is adapted to the feature image and such that a surface of the model object, which does not face a model sub-object, is adapted to the object image, characterized in that the feature image generation unit comprises a distance unit for performing a distance transformation on the feature image, wherein the feature image comprises feature image elements, to which feature image values are assigned, wherein the distance transformation is performed in accordance with following steps: - determining intermediate region feature image elements of the feature image elements, wherein the intermediate region feature image elements show features related to intermediate regions between the sub-objects, - determining a distance value for a feature image element, wherein the distance value depends on the distance between a determined intermediate region feature image element and the feature image element for which a distance value is to be determined, - replacing the feature image value, which is assigned to the feature image element for which the distance value has been determined, by the determined distance value. - a feature image generation unit for generating a feature image showing features related to intermediate regions between the sub-objects from the object image, wherein the feature image generation unit comprises a feature enhancing unit for enhancing features related to intermediate regions between the sub-objects in the object image, - a segmentation unit for segmenting the sub-objects by using the object image and the feature image, wherein the segmentation unit comprises: - a model providing unit for providing a model object comprising model sub-objects (13, 14, 15, 16, 17), - a pre-positioning unit for pre-positioning the model object in the object image and the feature image, and - an adaptation unit for adapting the model object to the object in the object image and in the feature image, wherein the adaptation unit is adapted such that a surface of a model sub-object facing another model sub-object is adapted to the feature image and such that a surface of the model object, which does not face a model sub-object, is adapted to the object image, characterized in that the feature image generation unit comprises a distance unit for performing a distance transformation on the feature image, wherein the feature image comprises feature image elements, to which feature image values are assigned, wherein the distance transformation is performed in accordance with following steps: - determining intermediate region feature image elements of the feature image elements, wherein the intermediate region feature image elements show features related to intermediate regions between the sub-objects, - determining a distance value for a feature image element, wherein the distance value depends on the distance between a determined intermediate region feature image element and the feature image element for which a distance value is to be determined, - replacing the feature image value, which is assigned to the feature image element for which the distance value has been determined, by the determined distance value. - determining intermediate region feature image elements of the feature image elements, wherein the intermediate region feature image elements show features related to intermediate regions between the sub-objects, - determining a distance value for a feature image element, wherein the distance value depends on the distance between a determined intermediate region feature image element and the feature image element for which a distance value is to be determined, - replacing the feature image value, which is assigned to the feature image element for which the distance value has been determined, by the determined distance value.