Wednesday, October 01, 2014

Radiofrequency Ablation

 Here is a really peculiar use of radio waves. That image above is from the cover of a medical text book edited by Shoei Huang and David Wilber. Were this a much older medical text book it would sound like quackery... but this is quite real. Amazingly it is not a new idea. while only in vogue abotu less than 20 years, it was actually first conceived in 1891 by Jacques Arsene d'Arsonval. He described heating of tissue when the RF waves pass through living tissue. In 1882 Jacques became head of the laboratory of biophysics, at Collège de France in Paris. He died in 1940 surely knowing by then that he was right, btu not seeing much in the way of practical application. He also invented a type of galvanometer and the thermocouple ammeter. I'll get back to him another day.

Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. I think you can now guess what Radio frequency ablation (RFA) is.   Yes, it's zapping away bits of oneself that have gone bad. This use of RF replaces the previously used as a "high frequency alternating current." the FDA considers it "minimally invasive" and thus is can be an outpatient procedure.

This ray-gun like treatment is performed usually with local anesthetic. The frequency is usually from 350 to 500 kHz. Though one 2004 text I read described a range of 10 kHz - 2.9 GHz to be "well-defined."  That was somwwhat concerning.  A probe is inserted into the organ in question and it can zap away cancerous growths modern applications include lung tumors, pancreatic cancer and bile duct cancer. It's a bit more obscure but it's also used to destroy "abnormal electrical pathways" in the heart.

It has some advantages. Because nerves and muscles respond to electrical charges it's much saver than the old AC and DC treatments. The human body, being more-or-less a bag of salt water, is a poor conductor. So when radio waves pass through it energy is lost as heat or "moving ions." In medical texts this is called "ionic agitation." Yes, they are cooking your tumor. Dessicated tissue functions as insulation for the surrounding tissue further increasing the current density. It can eventually result in "charring."  While this is very nice on BBQ, it's kind of gross if it's in my liver.