Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Patients will only be included after written informed consent. The preoperative CE-CT-thorax-scan yields little additional radiation exposure, which will however be negligible compared to the radiation treatment to be given because of the breast cancer. In addition, there is a small risk on an allergic reaction to the intravenous contrast, and on renal complications. Therefore, renal function will be checked prior to giving contrast. A kreatinine clearance < 60 ml/min will be a contra-indication for contrast. The pre-operative CT-scan will be made in MAASTRO clinic, requiring an additional visit to MAASTRO clinic. A possible benefit may be that the pre-operative CE-CT thorax may improve the definition of the target volume, and thereby reduce the risk on a local recurrence.