Biomedical Engineering Reference
In-Depth Information
massive. Dose-volume histogram analysis showed localized doses in the
tumor as high as 8000Gy (800 000 rad), but only 2.5% of the tumor
received more that 1000Gy (100 000 rad). It was estimated that 85%
of the tumor had been destroyed at the time of removal (approximately
six weeks).
Additional microdosimetry data should give a clearer picture of the
expected dose delivered to specific sites, thereby making possible a
more accurate assessment of the amount of radiation delivered to the
tumor(s) and to the healthy part of the liver. Ideally, this knowledge
could mean that even larger doses can be safely delivered in the future
without exceeding the radiation limit of 20-35Gy (3500 rad) for healthy
liver tissue.
13.7 TREATMENT OF KIDNEY CANCER: RENAL CELL
CARCINOMA
When discovered at an early stage, surgical removal of a diseased kidney
is the usual treatment of choice for patients with kidney cancer (renal
cell carcinoma). However, in cases where a malignant tumor is at an
advanced stage or has spread to other nearby organs, surgery may not be
possible owing to the risk that renal cancer cells will remain in the patient
and malignant tumors will reappear elsewhere, metastatic tumors. In
this case, treatment options are limited and generally unsatisfactory.
An alternative treatment for patients with inoperable kidney cancer is
to infuse the cancerous kidney/tumor with radioactive glass microspheres
for the purpose of quickly destroying the cancer cells in the kidney and
malignant tumor. Once the tumor and cancer cells are destroyed, and the
risk of viable cancer cells remaining in the body is greatly diminished,
the diseased kidney can be surgically removed.
The idea of destroying a diseased kidney prior to surgical removal has
been investigated in rabbits [25] using glass microspheres (20-40
min
diameter) made from a chemically durable glass that contained 7wt%
Sm
2
O
3
, 20wt% MgO, 21wt% Al
2
O
3
, and 52wt% SiO
2
. This glass
was made radioactive by neutron activation to form
153
Sm, which is
primarily a beta emitter with an imageable gamma ray (Table 13.1). In
in vivo
trials, using the same general technique as shown in Figure 13.7,
varying amounts of radioactive
153
Sm microspheres were injected into
the renal artery and deposited into one kidney of 18 healthy New
Zealand White rabbits. In this dose escalation experiment, the target
kidney received from 16 to 266 MBq of
153
Sm, corresponding to doses
μ
