Re-imaging my brain in San Francisco

In 2015 and again in 2018, I travelled to San Francisco to be a volunteer in a study of a then experimental PET scan for abnormal tau protein in the brain using a radioactive ligand called [¹⁸F]-AV1451. This radioactive ligand binds with high affinity to insoluble paired-helical filaments of hyperphosphorylated tau, the principal component of neurofibrillary tangles. Although my three-year follow up scans were delayed by the Covid-19 pandemic, I returned with my wife Lois this week for third set of studies spread over two days. What made this visit different, other than having to wear masks throughout the visit, was the presence of the film crew that is making a documentary film based on my book, A Tattoo on my Brain: A Neurologist’s Personal Battle against Alzheimer’s Disease. 

The first day was spent at the Sandler Neurosciences Center on the UCSF Mission Bay campus. I had several hours of cognitive testing, a comprehensive neurological exam, blood tests, and a high-resolution MRI scan of my brain to assess the amount of progressive loss of brain tissue. Lois was interviewed by psychologists for her take on my cognitive issues. The film team documented almost the entire day. Dr. Gil Rabinovici, the principal investigator for the study, and the entire team at the Sandler Neuroscience Center were amazingly accommodating and supportive of the film project. It was an exhausting day, but I think it was worth it.

The next day Lois and I and the film team headed across the San Francisco Bay to the PET scan site at Lawrence Berkeley National Laboratory, building 55. The project director there, Dr. William Jagust, and the lab staff were very gracious in accommodating the film project.  The scanning room at this site is connected by a pneumatic tube to a cyclotron two buildings away where the radioactive tracers are assembled. The beta-amyloid PET scan was performed using [¹¹C]-PiB (Pittsburg Compound B). As the radioactive carbon-11 (¹¹C) decays to boron-11, positrons are released and are detected by the scanner creating an image. This was the first successful ligand for amyloid PET scanning, and it still has features that make it an excellent choice such as low off target binding. The down side is that the radioactivity of ¹¹C decays with a half-life of only twenty minutes. After five half-lives or 100 minutes, there is no longer any detectable radioactivity. It currently is used only as a research tool as it requires an onsite cyclotron and a tightly coordinated injection minutes after assembly. For me, the experience of the ¹¹C-PiB scan entailed lying on my back in the scanner which is essentially a modified CT scanner.  A standard CT scan is first performed.  The radioactive ligand then arrives from the cyclotron through the pneumatic tube with a woosh and thunk.  At the precise pre-determined moment following assembly, the ligand was injected into a catheter in my arm with no discomfort.  Then I lay still for 90 minutes while positron detectors created images based on the location of radiation in my brain. I don’t begin to understand how this really works, but for me it was not hard at all.  I actually slept through most of it. The film crew was there taking shots of me from all directions and recording the pneumatic arrival of the ligand.

The tau PET scan followed after the amyloid scan and was somewhat anti-climactic as it takes only 30 minutes of scanning. The [¹⁸F]-AV1451 tracer has a half-life of 110 minutes so it is much easier to handle.  In fact, a version of [¹⁸F]-AV1451 has been FDA approved and is now marketed as Flortaucipir with offsite assembly. My tau PET scan used the onsite-assembled [¹⁸F]-AV1451.Both the amyloid and tau PET scans require post-processing to create the color-coded images we are familiar with.  Therefore, I was not able to see any of my scans on the day they were done, but I will be able to see them in a few weeks.  If it is OK with the study doctors, I will share the results on this blog and with the film makers at that time.