The substance concentration monitoring method includes non-invasively inserting a temperature probe into an area of the body where the substance concentration is measured. The internal temperature of the area is measured and an internal temperature signal is generated. An incident first near-infrared (NIR) beam within a first wavelength band is directed from the light source to a portion of the region, the first wavelength band including the wavelength at which the absorption peak of the NIR absorption spectrum of the substance exists. An incident second NIR beam in the second wavelength band is directed from the light source to a portion of the region and the material exhibits no or little absorption in the second wavelength band. The substance concentration is calculated based on the values corresponding to the internal temperature signal, the first initial power signal, the second initial power signal, the first substance concentration signal, and the second substance concentration signal.物質濃度監視方法は、物質の濃度が測定される体の領域に温度プローブを非侵襲的に挿入することを含む。領域の内部温度が測定され、内部温度信号が生成される。第一波長帯域内の入射第一近赤外線（ＮＩＲ）ビームが光源から領域の一部に向けられ、第一波長帯域は、物質のＮＩＲ吸収スペクトルの吸収ピークが存在する波長を含む。第二波長帯域内の入射第二ＮＩＲビームが光源から領域の一部に向けられ、物質は第二波長帯域内において吸収を全く又はほとんど示さない。内部温度信号、第一初期パワー信号、第二初期パワー信号、第一物質濃度信号、及び第二物質濃度信号に対応する値に基づいて、物質濃度が計算される。
