Image Processing Reference
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Figure4.2 Schematic of an x-ray shadowgram.
Figure4.3 Crookes tube schematic.
they cause powerful chemical reactions deep within tissue. Ultraviolet light is
dangerous for the same reasons, but it can only penetrate a few millimeters into
the skin, in contrast to X rays and gamma rays, which can easily travel all the
way through a person's body. These rays can damage cells deep within tissues
by causing ionization, a process whereby electrons are knocked off atoms and
molecules, making the ionized material much more chemically reactive than it
would be in an un-ionized state. The first indications that x rays were harmful
to tissue were damaged hands, since early x-ray technicians often used their hands
as test objects for medical x-ray equipment. After repeated exposure, they often
developed basal-cell skin cancer and other serious conditions. Figure 4.5 shows
the hands of Mihran Kassabian (1870-1910), an early x-ray researcher who died
of cancer that was almost certainly due to his high occupational x-ray dosage. His
condition required numerous amputations of fingers as the necrosis progressed.
Kassabian's laboratory is shown in Fig. 4.6. Note the numerous x-ray images on the
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