Biomedical Engineering Reference
In-Depth Information
Fig. 17.9.
Example of light dosimetry during PDT of prostate cancer, showing
the patient set-up, the placement of fibers and detector fibers through a template,
the multichannel light dosimeter measurements of the local light fluence rate as a
function of time during treatment at three different locations the graph shows: (
a
)
in the prostate, (
b
) the urethra and (
c
) the rectum
optical properties. One solution is to measure these properties separately and
apply a light propagation model to correct for the attenuation. Alternatively,
fiberoptic probes have been developed to reduce this attenuation dependence,
for example, by sampling only a very small tissue volume [22].
The measurement of oxygen levels in tissue is well-established, for example,
using interstitial microelectrodes or fiberoptic probes. Noninvasive measure-
ments are less well developed and do not directly measure the pO
2
, e.g., diffuse
reflectance spectroscopy can detect changes in the relative concentration of
