Appeal No. 2002-2110 Page 2
Application No. 09/224,748
According to the appellants, conventional radiographic techniques are prone to
miss small cracks. For example, the minimum width of a crack that can be detected by
computed tomography is about 40 µm; the minimum width of a crack that can be
detected by neutron radiograph, about 1mm. (Id. at 1-2.)
PET is a known technology for medical imaging. The invention applies PET,
however, to detect the presence of cracks and similar anomalies on surfaces of metallic
or mechanical parts and to locate those features with millimeter spatial resolution.
More specifically, a radioactive gas is directed onto the surface of a part to be
inspected. The gas is then pumped away, leaving a fraction of a monolayer of gas on
the surface. Coincident gamma-rays are detected to determine the location and shape
of cracks, voids, or porous regions and to calculate the width, depth, and length thereof.
The appellants assert, "[d]etection of 0.01µm wide by 10 µm deep cracks is possible
with the . . . invention." (Id. at 2.)
A further understanding of the invention can be achieved by reading the following
claim.
17. A method using positron-emission tomography for detecting
chemical surface features, comprising:
producing positron-emitting radioisotopes on the surface of a
material by activation of a pre-existing material containing positron-
emitting radioisotopes,
Page: Previous 1 2 3 4 5 6 7 8 9 10 11 Next
Last modified: November 3, 2007