Biomedical Engineering Reference
In-Depth Information
Inject radioactive
particles
Synovial membrane
Synovial cavity
Articular cartilage
Articular capsule
Bone
Periosteum
Figure 13.10
Concept of using biodegradable radioactive glass microspheres for
radiation synovectomy of rheumatoid arthritic joints. It is important that no radioac-
tivity ''leaks'' from the treated joint. (Modified from Ref. [27].)
injected with radioactive and non-radioactive microspheres, 5-15
min
diameter, made from lithium borate [9, 28] or lithium silicate glass [29].
In addition to degrading in the animal, the leakage of the radioisotope,
either
165
Dy or
90
Y, from the joint was much less than the 10-25%
observed when radiocolloids are used. Furthermore, no evidence has
been found that the glass microspheres cause any mechanical wear or
damage in the joint for periods up to six months.
Microspheres made from a dysprosium-lithium borate glass
(DyLB3-10 in Table 13.2) have been tested [9] for up to 64 days in
a simulated synovial fluid (SSF) at 37
◦
C and in the stifle joint of
Sprague Dawley rats [9] for 112 days. The SSF was a commercial
phosphate-buffered saline solution containing 0.3wt% hyaluronic acid
at pH
μ
7.4. Animals were sacrificed after 28 days for histological
examination of the stifle joint and at 112 days to determine the
condition of the microspheres, by scanning electron microscopy (SEM),
and the general condition of the joint.
Chemical analysis of the SSF solutions showed that the
in vitro
degradation of non-radioactive DyLB3-10 microspheres started within
6 hours, and within 12 hours the concentration of Li, B, and Dy in
solution had become nearly constant. After 64 days, the SSF contained
approximately 97% of the Li and 80% of the B in the initial glass, but
only 0.3% of the Dy in the microspheres had dissolved. Even though the
starting glass had nearly dissolved, 70-75% weight loss, only 0.3% the
Dy in the microsphere had been released to the solution.
Additional degradation experiments with radioactive DyLB3-10
microspheres, neutron activated to form the beta-emitting
=
165
Dy
