Chapter 14 Non-invasive in vivo imaging of transplant function

Positron emission tomography (PET) allows regional changes in brain metabolism, blood flow, and receptor binding to be detected in vivo and quantitated in both Parkinson's (PD) and Huntington's (HD) disease. Single photon emission tomography (SPECT) can also provide useful estimates of blood flow and receptor binding, and is more widely available than PET. It has the advantage that its longer-lived 123I and 99mTc-based tracers do not need to be manufactured on site, but is less sensitive than PET and susceptible to scatter artefact. There are two basic ways to use functional imaging when measuring the changes in regional cerebral function associated with neurodegenerative disorders and transplantation. First, abnormalities in resting regional cerebral metabolism, blood flow, and neuroreceptor binding can be studied in both the implanted tissue and the host brain. Second, patients can be asked to perform tasks while levels of regional cerebral blood flow are measured. In this way, the effects of stereotactically implanted tissue on patterns of regional cerebral activation can be studied in transplanted movement disorder patients.