A videofluoroscopic swallow study (VFSS) is a specialized X-ray procedure that allows healthcare providers to evaluate a patientâs ability to swallow. This test is particularly useful in the context of cancer, especially for patients who have had head and neck cancer or other types of cancer that may impact swallowing functions. During the VFSS, a series of X-ray images are taken as the patient swallows various substances of different consistencies.