Inclusion Criteria:  Female or male, Age ≥ 18 years at time of study entry. Undergoing systemic chemotherapy on a CVC. Having already received at least one course of treatment without difficulty. Coming for a new course of treatment authorised by the usual biological assessment. First episode of lack of CVC blood return despite the usual positioning and injection- aspiration manoeuvres No abnormality on inspection or palpation (turning) of the CVC. Patient has valid health insurance. Patient information and signature of informed consent.  Exclusion Criteria:  Previous episode of lack of CVC blood return whether explored or not. Patient currently treated in an interventional therapeutic trial. Patient with a Picc-line implantable device. Suspected CVC infection or thrombosis. Planned chemotherapy with vesicant agent (anthracyclines). Possible CVC disjunction. Allergy to X-ray contrast agent or creatinine clearance below 30ml/min prohibiting an iodine injection. Pregnant, likely to be pregnant or breastfeeding woman. Persons deprived of their liberty, under a measure of safeguard of justice, under guardianship or placed under the authority of a guardian. Impossibility of undergoing medical monitoring of the trial for geographical, social or psychological reasons, social or psychological reasons.