The present invention provides a monitoring system, which comprises a novel needle, and an optical signal generating device, wherein at least one optical signal output of the optical signal generating device is coupled to the optical core of the needle, and it further comprises an ultrasound (US) transducer,and a processor adapted to direct the US transducer to transmit an US signal into a region of a subject in which the needle is moving and receive an US signal reflected in the region in response to the transmitted US signal in a US measurement sub-cycle of a measurement cycle, and to direct the optical signal providing device to transmit an optical signal having a unique wavelength from the dome of the needle into an area of the region and direct the US transducer to receive a photo-acoustic (PA) signal induced in the area in response to the optical signal in each of at least one PA measurement sub-cycle of the measurement cycle, and reconstruct an US image from the US signal received in the US measurement sub-cycle.
