A patient monitoring system (70) comprises a threshold determining unit (71) configured to determine a cut-off threshold value based on a signal representing a reflection response of a skin of a patient (30) and a signal representing a reflection response of a patient covering object (32). The patient monitoring system (70) also comprises a signal processing unit (71) configured to process a reflection signal, representing a detected wave reflected from at least a portion of the patient (30), based on the cut-off threshold value to cut off a portion of the reflection signal corresponding to detected wave reflected from the patient covering object (32) to get a processed reflection signal corresponding to detected wave reflected from the surface of the patient (30).
