Surgery – Diagnostic testing – Respiratory
Patent
1997-06-06
1999-10-12
Asher, Kimberly L.
Surgery
Diagnostic testing
Respiratory
600532, 73 233, 422 84, 422100, 422101, G01N 122, B01L 300, A61B 5083, A61B 5097
Patent
active
059647124
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP96/02876 filed on Oct. 2, 1996.
TECHNICAL FIELD
The present invention relates to methods and apparatuses for spectrometrically measuring the concentration of an isotopic gas on the basis of a difference in the light absorption characteristics of the isotope.
BACKGROUND ART
Isotopic analyses are useful for diagnosis of a disease in a medical application, in which metabolic functions of a living body can be determined by measuring a change in the concentration or concentration ratio of an isotope after administration of a drug containing the isotope. In the other fields, the isotopic analyses are used for studies of the photosynthesis and metabolism of plants, and for ecological tracing in a geochemical application.
It is generally known that gastric ulcer and gastritis are caused by bacteria called helicobacter pylori (HP) as well as by a stress. If the HP is present in the stomach of a patient, an antibiotic or the like should be administered to the patient for bacteria removal treatment. Therefore, it is indispensable to check if the patient has the HP. The HP has a strong urease activity for decomposing urea into carbon dioxide and ammonia.
Carbon has isotopes having mass numbers of 12, 13 and 14, among which .sup.13 C having a mass number of 13 is easy to handle because of its non-radioactivity and stability.
If the concentration of .sup.13 CO.sub.2 (a final metabolic product) or the concentration ratio of .sup.13 CO.sub.2 to .sup.12 CO.sub.2 in breath of a patient is successfully measured after urea labeled with the isotope .sup.13 C is administered to the patient, the presence of the HP can be confirmed.
However, the concentration ratio of .sup.13 CO.sub.2 to .sup.12 CO.sub.2 in naturally occurring carbon dioxide is 1:100. Therefore, it is difficult to determine the concentration ratio in the breath of the patient with high accuracy.
There have been known methods for determining the concentration ratio of .sup.13 CO.sub.2 to .sup.12 CO.sub.2 by means of infrared spectroscopy (see JPB 61(1986)-42219 and JPB 61(1986)-42220).
In the method disclosed in JPB 61(1986)-42220, two cells respectively having a long path and a short path are provided, the path lengths of which are adjusted such that the light absorption by .sup.13 CO.sub.2 in one cell is equal to the light absorption by .sup.12 CO.sub.2 in the other cell. Light beams transmitted through the two cells are lead to spectrometric means, in which the light intensities are measured at wavelengths each providing the maximum sensitivity. In accordance with this method, the light absorption ratio can be adjusted to "1" for the concentration ratio of .sup.13 CO.sub.2 to .sup.12 CO.sub.2 in naturally occurring carbon dioxide. If the concentration ratio is changed, the light absorption ratio also changes by the amount of a change in the concentration ratio. Thus, the change in the concentration ratio can be determined by measuring a change in the light absorption ratio.
(A) However, the method for determining the concentration ratio according to the aforesaid document suffers from the following drawbacks.
Calibration curves for determining the concentrations of .sup.12 CO.sub.2 should be prepared by using gaseous samples each having a known .sup.12 CO.sub.2 concentration.
To prepare the calibration curve for the .sup.12 CO.sub.2 concentration, the .sup.12 CO.sub.2 absorbances are measured for different .sup.12 CO.sub.2 concentrations. The .sup.12 CO.sub.2 concentrations and the .sup.12 CO.sub.2 absorbances are plotted as abscissa and ordinate, respectively, and the calibration curve is determined by the method of least squares.
The calibration curve for the .sup.13 CO.sub.2 concentration is prepared in the same manner as described above.
For determination of the concentrations by means of infrared spectroscopy, the preparation of the calibration curves is based on an assumption that the relation between the concentration and the absorbance conforms to the Lambert-Beer Law. However, the Lambert-Beer Law itself is an a
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patent: 3734692 (1973-05-01), Lucker et al.
patent: 5131387 (1992-07-01), French et al.
patent: 5543621 (1996-08-01), Sauke et al.
S. Tetsyo, "13C Exhalation Gas Inspecting System", Patent Abstracts of Japan, vol. 96, No. 006 (1996).
K. Nobuhiko, "Method and Device for Collecting Exhalation", Patent Abstracts of Japan, vol. 96, No. 10 (1996).
K. Kouichi, "Method and Equipment for Measuring 13 C02", Patent Abstracts of Japan, vol. 10, No. 157, Jan. 1986.
Hamao Tamotsu
Ikegami Eiji
Kubo Yasuhiro
Maruyama Takashi
Mori Masaaki
Asher Kimberly L.
Otsuka Pharmaceutical Co. Ltd.
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