Biomedical Engineering Reference
In-Depth Information
growth of a tumor, but also reducing the size of an existing tumor.
The overall effectiveness of
in situ
irradiation should be expected to
depend upon many factors, such as the characteristics (vascularity) of
a specific tumor, the energy and range of the radiation, the half-life
of the beta-emitting radioisotope, and the amount of radioactive isotope
inside the tumor(s). Since REAS glasses containing a preferred beta-
emitting radioisotope can be easily prepared, it is possible to select the
most effective beta-emitting radioisotope for treating a particular type
of tumor in a specific organ. In other words, it is possible to tailor-make
an
in situ
radiation delivery vehicle that is optimized for a specific organ
or type of tumor.
In the work undertaken to date, only REAS glasses containing a
single radioactive element have been used for the
in situ
irradiation
of diseased organs. However, REAS glasses containing two or more
neutron activatable RE elements are easily prepared, so a target organ
could be irradiated simultaneously with radiation emitted from several
radioisotopes for enhanced effectiveness. Combining several neutron
activatable radioisotopes of different half-lives and emission energies
into a single glass could be advantageous in optimizing the irradiation of
tumors of different size and in delivering the radiation dose over a time
period not attainable with a single radioisotope. Another alternative
would be to blend two or more REAS glasses, each of which contains a
different neutron activatable element, so that the delivered dose consists
of a combination of radiation type, energy, and half-life.
13.6 TREATMENT OF LIVER CANCER:
HEPATOCELLULAR CARCINOMA
Liver cancer (hepatocellular carcinoma) is difficult to treat since there
are commonly few symptoms until the life of the patient is in peril.
Approximately 18 500 primary tumors of the hepatic and biliary tree
are diagnosed each year, which result in an estimated 12 300 deaths [13].
The number of metastatic liver tumors diagnosed each year is estimated
to be roughly 10 times the number of primary tumors.
At the time of diagnosis, surgery is often not an option because of
the presence of multiple tumors and the difficulty in removing them
completely. External beam radiation is generally ineffective since the
maximum dose that can be delivered is limited by the damage to
nearby healthy tissue and is typically too small to destroy the tumor(s).
Chemotherapy by itself usually provides only temporary improvement.
