Biomedical Engineering Reference
In-Depth Information
on the assumption, likely although yet unproven, that thermal
effects are a significant contributor to the overall outcome.
Systemic toxicity for a salt must also be considered. The initial
choice of acetic acid and sodium hydroxide to produce sodium
acetate was at best an educated guess. Our reasoning was that
there is prior clinical experience with acetic acid alone as noted
earlier, the amount of energy released although intermediate
appeared adequate, and the salt is readily converted in the body
to bicarbonate.
39
Indeed, it is actually difficult to measure serum
acetate concentrations for this reason.
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19.2 Future Directions
There are many avenues that could provide fruitful opportunity to
explore in the future in the realm of thermochemical ablation. As
a thermal method, a natural question concerns the thermal dose
and the distribution of that dose. Thus, various methods of ther-
mometry and thermography will play an important role in delin-
eating what is occurring within a treated area over time. Another
obvious one is that to date this new method has not been tested
against tumors in vivo. With regard to performance, differences
in hydraulic conductivity between tumor and surrounding tissues
can be substantial. Certain typically encapsulated tumors, such as
HCC in a cirrhotic liver, may respond well, but a role for an inject-
able therapy in metastatic disease surrounded by normal, nonfi-
brotic tissue is less clear. Perhaps a single-agent thermochemical
ablation such as with an energetic electrophile distributed in small
volumes via a multi-tined needle will prove beneficial. No doubt
device development will be essential in achieving better results
than those obtained with relatively crude prototypes. Studies to
date have only been conducted in the acute setting. Much work
remains to truly understand the physiology and safety profile for
any particular reaction in survival settings ranging from acute to
chronic. Determination of the mechanisms of action will be key
to understanding this technique. These will be different depend-
ing on the conditions chosen, but some common themes will likely
emerge related to temperature, concentration, and Hofmeister
effects to begin with. Imageable agents have not yet been shown to
perform satisfactorily in vivo, though
ex vivo
results are encourag-
ing and the chemistry appears to be consistent. Lastly, it is also pos-
sible that other applications not directly related to tumor therapy
could be considered. Virtually anywhere that hyperthermia is used
for therapeutic purposes could provide a starting point for further
research. Given the simplicity, ready availability, and relative safety
of this concept, it appears that there is much opportunity in the
field of thermochemical ablation for future research.
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2010;46(4):744-751.
