Biomedical Engineering Reference
In-Depth Information
In the early human trials, it was anticipated that a patient would
receive a single injection of beta-emitting radioactive microspheres,
because there was little information available for judging the effect of
such large doses on the target organ. However, the early patients with
liver cancer tolerated doses up to 150Gy quite well and, as confidence
in the safety of these large doses has increased, an increasing number
of patients have received repeated injections (two to four) of the
90
Y
microspheres, with no reported ill effects. In one case, a male with
inoperable liver cancer received eight injections of
90
Y microspheres (at
150Gy per injection) over a four-year period with no ill effects.
13.5.4 Tumor Response and Tailoring of Glass
Composition
The response of tumors receiving
in situ
beta irradiation from REAS
glass has been demonstrated in animal experiments [19, 20] as well as
in humans [2, 3, 16, 21]. In an animal experiment [19], the growth (or
lack thereof) was determined for tumors in six nude mice that had been
injected with approximately 2
10
7
BT-20 cells (human mammary
carcinoma). The tumor in each mouse was allowed to grow for 14
days, at which time the tumor was injected directly with either 5mg
of radioactive
×
166
HoAS glass particles (
Ci/tumor) or 5mg of
non-radioactive HoAS glass particles. The volume of the tumor was
measured at the time it was injected with the HoAS glass particles and
12 days later.
As shown in Figure 13.5, the volume of the tumor for each animal
(numbers 1, 2, and 3) in the control group, injected with non-radioactive
HoAS glass, continued to grow significantly, as expected. However, the
volume of the tumors injected with the radioactive
166
HoAS glass
particles, either decreased, animals 4 and 5, or remained the same,
animal 6.
In the second experiment [20], varying amounts of radioactive
90
YAS
glass microspheres (20-25
∼
200
μ
m in diameter) were injected directly into a
tumor (produced from SMMC-7721 cells) that had been induced in nude
mice. As is evident from Figure 13.6, the tumor growth that occurred in
each animal during the 14 days after injection was significantly less with
increasing quantity of radioactive
90
YAS glass microspheres.
These two examples show that the
in situ
beta radiation from REAS
glass containing
166
Ho or
μ
90
Y is effective in not only preventing the
