Endpoints subproject 1: To develop a reproducible method for the detection of lymph nodes by DECT in operation specimens from rectal resection for cancer. sub project 2: Primary endpoint: To evaluate the sensitivity and specificity for malignant lymph nodes in vitro RC specimens compared with histopathology. Secondary endpoint: To assess DECT as imaging tool for the diagnosis of malignant lymph nodes at RC. Histopathology will be used as reference.Subproject 3: Primary endpoint: To compare the sensitivity, specificity, positive- and negative predictive values, accuracy of DECT and standard MRI. Secondary: To evaluate the value of the gold standard for the use of imaging methods for the description of the lymph node, validated by histopathology. Secondary: to determine the value of tumor diagnostics using DECT.subproject 4: To assess the value of DECT as imaging tool for diagnosing response to chemo radiotherapy of malignant lymph nodes.