A probe system spectral absorption (300) using the spectral absorption properties of the arterial blood and the dynamics of time-dependent blood flow, which is the change in blood volume in the artery due to the pulse of a patient, assessing the proximity to the artery (302), comprising: a light source (304) for generating excitation light (306) having a wavelength suitable for absorption by chromophores in the blood an optical excitation fiber (308) for bringing said excitation light near the artery an optical collection fiber (310) separate from the excitation optical fiber (308) to capture backscattered light from the artery a light detector (312) operatively connected to said optical fiber collection to generate an oscillating signal that varies with time in a periodic fashion to represent the change in blood volume in the artery due to the cardiac cycle and a signal processor (314) operatively connected to said light detector for determining a distance (320) to said artery based on said backscattered light and the Beer-Lambert law of light absorption using an amplitude of said signal oscillating and a value for attenuation coefficient of the surrounding tissue (μef).Un sistema de sonda de absorción espectral (300) que usa las propiedades de absorción espectral de la sangre arterial y la dinámica del flujo sanguíneo dependiente del tiempo, que es el cambio en el volumen sanguíneo en una arteria debido al pulso de un paciente, para evaluar la proximidad a la arteria (302), que comprende: una fuente luminosa (304) para generar luz de excitación (306) que tiene una longitud de onda adaptada para su absorción por cromóforos de la sangre una fibra óptica de excitación (308) para llevar dicha luz de excitación cerca de la arteria una fibra óptica de recogida (310) separada de la fibra óptica de excitación (308) para capturar la luz retrodispersada de dicha arteria un detector de luz (312) conectado operativamente con dicha fibra óptica de recogida para generar una señ
