Week 7 - Andrew

The clinical highlight for this week also occurred at Columbia Presbyterian, involving the GammaKnife. This time, however, I was intrigued by the industry of the was Dr. Pannullo administered the procedure rather than the necessary science. Dr. Pannullo had three patients, each with a different issue that could be treated with radiation. The first patient had an aggravated nerve that caused him jaw pain. Previous treatment had been done to decompress a vessel that was very close to the nerve and the hypothesis was that the vessel was impinging on the nerve causing the pain. This treatment reportedly only worked for a short period and then the pain came back. An alternative treatment for this issue is to hit the nerve with some radiation, enough to damage but not enough to kill, to desensitize the nerve. The treatment plan for this patient, based on a high resolution MRI, was crucial because the target was very small and irregularly shaped (as in non-spherical), and surrounded by critical tissue. The second patient had a small possibly malignant lesion in his brain and the treatment for this was pretty straightforward. The third patient was a woman who had had a very large metastatic lesion removed previously and now there were neoplasms around the resection cavity edges. The doctors decided to be quite generous with this patient's treatment plan to try to delay further recurrence as long as possible. What was amazing was that all of these patients were treated with the GammaKnife in the same day, in a staggered schedule. It was really cool to observe the procession of the patients to be time-efficient.

In terms of research, I was attempting to melt poly(lactide-co-caprolactone) (PLC) into a thin film basically, to evaluate its utility for the biodegradable brachytherapy device. The slight challenge with this, exacerbated by my lack of equipment, was that when the polymer melts from the granules into one mass, it makes a blob a few millimeters thick and has to be pressed to make a thin film. To achieve this I obtained some aluminum foil, melted the polymer onto it, and then used another piece of foil on top of it and pressed down with the flat end of a syringe plunger. Unfortunately, the plastic of the syringe didn't hold up to the temperature and began to melt, so I was unable to press the polymer down uniformly. Also, I found that once the polymer cooled it stuck to the foil strongly and I was not able to remove the polymer for the foil by any means. To address this I used vacuum grease that was provided to me by the lab tech, and found that a very thin coating of the grease prevented sticking. After a few iterations of insulating the plunger of the syringe from the heat I found that I was still unable to get an evenly thin polymer once cool. I returned to Dr. Wernicke to tell her the challenge that I was facing and tell her that I needed more than just a hot plate and foil, and she was able to obtain for me two 1 inch thick pieces of steel to try to press the polymer with. The steel pieces were flat on one side but had deep, wide grooves in the other, so it turned out to be difficult to uniformly heat to the correct temperature (I didn't have a thermometer to use on the upper surface of the bottom steel piece, so I had to just guess where this was). However, despite this issue and issues with some air bubbles in the polymer once melted, I am fairly certain that I have identified an appropriate polymer that is biodegradable and has the elastic properties necessary to be able to be expanded into a balloon by hand. Of course, this is based on my ability to stretch the polymer between my fingers alone. Nevertheless, I was impressed with the elasticity of PLC and believe it would be very useful for the device I was assigned to design.