Method and device for measuring concentration of component
A pressurizing unit applies pressure around a measurement site of a measurement subject so as to suppress blood flow at the measurement site during a set pressurizing time. While the pressurizing unit is applying pressure around the measurement site, a detection unit detects a photoacoustic signal generated at the measurement site irradiated with a light beam. The detection unit detects a photoacoustic signal when a preset time has elapsed after the pressurizing unit started to apply pressure around the measurement site.
1 . A component concentration measuring method comprising:
a first step of suppressing blood flow in a measurement site of a measurement subject by applying pressure around the measurement site;
a second step of irradiating the measurement site with a light beam having a wavelength that is absorbed by a measurement target substance, and detecting a photoacoustic signal generated at the measurement site when a set time has elapsed after the pressure of the first step has started to be applied around the measurement site;
a third step of obtaining a concentration of the measurement target substance using the photoacoustic signal;
a fourth step of stopping applying pressure around the measurement site after detecting the photoacoustic signal; and
periodically repeating the first step of starting applying the pressure, the second step of detecting the photoacoustic signal, and the fourth step of stopping applying the pressure, wherein a period from a first start of applying the pressure of the first step to a second start of applying the pressure of the first step equals an interval of vasomotion of a blood vessel at the measurement site, wherein the set time in the second step is (T−Δt)/2, and a time during which applying the pressure is stopped in the fourth step is (T+Δt)/2, wherein T is the period from the first start of applying the pressure to the second start of applying the pressure, and Δt is a duration of detecting the photoacoustic signal in the second step wherein the measurement target substance is glucose.
2 . The component concentration measuring method according to claim 1 , wherein the period from the first start of applying the pressure to the second start of applying the pressure is between 5 and 20 seconds, wherein the first start and the second start are applied consecutively.
3 . A component concentration measuring device comprising:
a light emitting device configured to irradiate a measurement site of a measurement subject with a light beam having a wavelength that is absorbed by a measurement target substance;
a pressurizing device configured to suppress blood flow in the measurement site by applying pressure around the measurement site;
a detector configured to detect a photoacoustic signal generated at the measurement site irradiated with the light beam emitted from the light emitting device while the pressurizing device is applying pressure around the measurement site, wherein the detector is configured to detect the photoacoustic signal when a preset time has elapsed after the pressurizing device has started applying pressure around the measurement site;
a concentration calculator configured to obtain a concentration of the measurement target substance using the photoacoustic signal; and
a controller configured to:
control a pressurizing operation that is performed by the pressurizing device and a photoacoustic signal detection operation that is performed by the detector;
periodically repeat causing the pressurizing device to start applying the pressure,
causing the detector to detect the photoacoustic signal, and causing the pressurizing device to stop applying the pressure; and
set a period from a first start of applying the pressure to a second start of applying the pressure to an interval of vasomotion of a blood vessel at the measurement site, wherein the preset time set for detecting the photoacoustic signal is (T−Δt)/2, and a time during which applying the pressure is stopped is (T+Δt)/2, wherein T is the period from the first start of applying the pressure to the second start of applying the pressure, and Δt is a duration of detecting the photoacoustic signal by the detector wherein the measurement target substance is glucose.
4 . The component concentration measuring device according to claim 3 , wherein:
the controller sets the period from the first start of applying the pressure to the second start of applying the pressure to 5 to 20 seconds, wherein the first start and the second start are applied consecutively.
5 . The component concentration measuring device according to claim 3 , wherein the light emitting device is configured to emit the light beam having a wavelength absorbed by glucose.