Radiant energy – Invisible radiant energy responsive electric signalling – With means to inspect passive solid objects
Patent
1995-08-10
1997-09-30
Glick, Edward J.
Radiant energy
Invisible radiant energy responsive electric signalling
With means to inspect passive solid objects
250308, 250393, G01T 129
Patent
active
056728760
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and apparatus for measuring distribution of a radioactive nuclide in a subject by using autoradiography, and more specifically to a measuring method and apparatus to examine distribution of a radioactive nuclide in a subject sample for the purposes of a safety test of drugs or others. In particular, the invention relates to a method and apparatus for measuring distribution of a radioactive nuclide in a subject, which can compensate for differences in density between respective parts of the subject for determining correct distribution of the radioactive nuclide.
BACKGROUND ART
Heretofore, autoradiography has been known as a method for directly recording distribution of a radioactive material in a sample in the form of a photograph.
Specifically, the autoradiography is performed by placing a film closely to, e.g., a sample which contains a radioactive nuclide as a tracer, and exposing the film to ionizing radiation emitted from the sample with a view to determine distribution of the radioactive nuclide deposited in specific parts of the sample.
Such a technique has been especially employed for a safety test of drugs. In a safety test, a drug labeled with a radioactive nuclide is first prepared. The drug is then injected to a laboratory animal such as a rat or a mouse. After a predetermined period of time, the laboratory animal is frozen and sliced to form specimens. After drying the specimens, distribution of the radioactive nuclide in the specimens is measured to thereby determine to which parts of the subject the drug has reached.
In practice, .sup.14 C of 3 to 5 MBq/weight kg is typically applied as a radioactive nuclide and the laboratory animal is frozen and sliced into specimens each having a thickness of 30 to 90 .mu.m after the predetermined period of time. Here, the maximum range of .beta.-ray radiated from .sup.14 C is on the order of 25 mg/cm.sup.2.
Certainly, to which parts of the subject the injected drug has reached can be determined by employing the above-described technique.
It is also often desired to determine to which parts of the subject the drug has reached in what amounts.
To meet such a demand, in the conventional autoradiography, the amounts of a radioactive nuclide in respective parts of the subject have been measured by exposing each of the frozen and sliced specimens to an X-ray film or an image sensing plate (for RLG, radioluminograpy), and determining an exposure of the film or a PSL value indicating the amount of PSL (photostimulated luminescence) (in the case of radioluminography, RLG).
Meanwhile, in measurement utilizing a photographic action or photostimulated luminescence by radiation, the parameter which comes up in discussion about radioactivity distributed in internal organs is a thickness of the specimen that is expressed by weight per unit area length (.mu.m).
In this respect, the measuring method using the conventional autoradiography in which only a thickness (.mu.m) of each prepared specimen is indicated suffers from a problem discussed below.
Even if the specimens have the same thickness (.mu.m), internal organs have different densities and water contents from each other and, therefore, radiation is absorbed by the internal organs themselves in different amounts. Consequently, a black tone (of the exposed X-ray film) or a PSL value per unit radioactivity is different for each of the internal organs.
As a result, the black tone of the film or the PSL value is not uniquely in match with the amounts of the radioactive nuclide in different parts of the subject, making it impossible to correctly evaluate distribution of radioactivity in the internal organs of the subject.
To correctly examine distribution of radioactivity in the internal organs of the subject, therefore, to which parts of the subject the drug has reached in how much amounts has been conventionally determined by burning internal organs of a laboratory animal injected with .sup.14 C in a like manner, and measuring the absolute amount of the radi
REFERENCES:
patent: 3812360 (1974-05-01), Tkyva
patent: 4777367 (1988-10-01), Kawasaki et al.
patent: 5289008 (1994-02-01), Jaszczak et al.
Glick Edward J.
Nemoto & Co. Ltd.
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