Week 6 - Andrew

This week started for me in Ithaca, where I spent Monday working on revisions for a paper that had just come back from peer review. The deadline was quickly upcoming and I had meant to just spend the weekend working on the revisions, but they spilled over into Monday. It was much easier for me to work in Ithaca because this was a review paper and all of the papers I used as reference were printed out in my office. Anyway, I was back on Tuesday and at work at Columbia Presbyterian with Dr. Pannullo at 6am. This turned out to be my clinical highlight of the week, unexpectedly. Dr. Pannullo had a patient with an areteriovenous malformation (AVM) in her brain (posterior right temporal I believe) that had been treated previously, but hadn't been treated completely. Previous treatment had been surgery: a surgeon had actually cut in and injected a sort of glue into the AVM with the intent of plugging it up to prevent possible hemorrhage in the future. Unfortunately this AVM hadn't been occluded completely and there was still some residual blood flow through the AVM. To treat this, Dr. Pannullo decided to perform steriotactic radiosurgery using a precise machine called the GammaKnife to ablate the remaining blood vessels. Interestingly, the difficult, or at least labor intensive, portion of this procedure was the pre-treatment imaging to identify exactly where to ablate with the radiation. First, the patient got an MRI, and then an MRA (essentially just an MRI with contrast to visualize the vessels that can carry blood flow). The image produced by the MRA was incomplete because the glue confounded the imaging, so to be safe Dr. Pannullo also ordered a CT angiogram which was fascinating. The patient was knocked out and a catheter was fed into her groin and up through her carotid artery into the brain vasculature. Then, X-ray dense contrast was injected into the brain vasculature and CAT scans were recorded at a rate of 3/s. It was incredible to see the contrast flow through the right hemisphere of the brain in basically real-time. First the contrast showed up against a white background at the surface of the brain and then entered the brain and virtually disappeared as it entered capillary beds, then then finally it coalesced into veins and left the brain. It all happened really fast and I was impressed with the doctors' ability to see the contrast agent accumulate briefly in residual AVM vessels. Next, guided by the MRA and CT scans simultaneously, Dr. Pannullo and the medical physicist outlined very precise and concentrated locations for the radiation to be shot on the computer, and the patient went into the machine for about 20 minutes and the procedure was over. Considering what this procedure was able to accomplish (at least ideally), this whole process was seemingly very quick and relatively painless.

In terms of research, I finally made some steps towards the lab bench stage of constructing a medical device. This was certainly not simple do to the fact that Dr. Wernicke does not have a lab or any equipment at her disposal. First, I had to try to melt the polymer PLC using a hot water bath (this is, once she returned my emails after I hadn't heard from her for a few days and found a lab to work in on my own at Columbia). The hot water bath was less than ideal because it cannot get very hot (the melting temp of the most promising polymer is slightly above 100 dC) and the polymer is biodegradable via hydrolysis. Ultimately, the hot water bath was insufficient to melt the polymer, but there was no great loss because I was able to salvage most of the polymer that I had experimented with, and it was a free sample anyway. I returned to Dr. Wernicke to tell her that I needed something hotter, like a hot plate, and she got me into Dr. Kaplitt's to use a hot plate. The hot plate proved hot enough to melt the polymer, although it took significant amounts of time to fully melt the polymer at about 150 dC, however once cooled the polymer was not nearly compliant enough to be able to form a bubble with. As an aside, I should mention that the polymer has to be melted because the form that I got it in is very small granules. I decided that I would need to produce a very thin sheet of the polymer in order to evaluate the mechanical properties, so I would have to return to the lab next week to try to produce this given my extremely limited resources. I should also mention that other polymers that I received as free samples, PC and PLG that I had little hope for, proved to have unacceptable elastic properties upon melting.