A device, suitable for the measurement of quantitative photon absorption coefficient (μ a) in tissue, the device comprising: - a first light source configured to generate ultrasound in the tissue; - a second light source provided for providing light for the deduction of the amount of light from the first light source actually entering a defined volume element in the tissue; - a light measurement element suitable for measuring at least one of: the intensity, the frequency, the frequency deviations and phase shift of the light to be measured; - an ultrasound source, suitable for the generation of a defined sound wave pattern in the defined volume element within the tissue, wherein the focus of the ultrasound wave field applied by the ultrasound source defines said volume element, and suitable for labelling the light originating from the second light source that enters the defined volume element within the tissue; - an ultrasound measurement element suitable for measuring ultrasound originating from the defined volume element within the tissue and generated by the light of the first light source that enters the defined volume element within the tissue; - a processor which is at least in communicative contact with the light measurement element and the ultrasound measurement element and wherein the processor is configured to deduce from the information provided by the light measurement element which portion of the light originates from the defined volume element; and characterized in that - the processor is further configured to deduce from the amount of light generated by the second light source, and from the amount of labelled light originating from the defined volume element, an amount of light originating from the first light source actually entering the defined volume element; and in that - the processor is further configured to deduce from the measured sound, generated in the defined volume element within the tissue by the first light source, and the amount of light from the first light source actually entered the defined volume element within the tissue, a specific photon absorption coefficient (μ a) of the defined volume element within the tissue. - a first light source configured to generate ultrasound in the tissue; - a second light source provided for providing light for the deduction of the amount of light from the first light source actually entering a defined volume element in the tissue; - a light measurement element suitable for measuring at least one of: the intensity, the frequency, the frequency deviations and phase shift of the light to be measured; - an ultrasound source, suitable for the generation of a defined sound wave pattern in the defined volume element within the tissue, wherein the focus of the ultrasound wave field applied by the ultrasound source defines said volume element, and suitable for labelling the light originating from the second light source that enters the defined volume element within the tissue; - an ultrasound measurement element suitable for measuring ultrasound originating from the defined volume element within the tissue and generated by the light of the first light source that enters the defined volume element within the tissue; - a processor which is at least in communicative contact with the light measurement element and the ultrasound measurement element and wherein the processor is configured to deduce from the information provided by the light measurement element which portion of the light originates from the defined volume element; and - the processor is further configured to deduce from the amount of light generated by the second light source, and from the amount of labelled light originating from the defined volume element, an amount of light originating from the first light source actually entering the defined volume element; and in that - the processor is further configured to deduce from the measured sound, generated in the defined volume element within the tissue by the first light source, and the amount of light from the first light source actually entered the defined volume element within the tissue, a specific photon absorption coefficient (μ a) of the defined volume element within the tissue.