Friday April 27 2007
CEA
High-resolution PET brings great promise: initial trialing on the HRRT lens gives conclusive results
J Nucl Med. (2007) 48(4): 538-546.
CEA
Challenges: to further extend our explorational capabilities and enable earlier detection of neurobiological changes in small, complex brain regions
The HRRT lens dedicated to brain research and recently installed at the SHFJ is currently in the testing phase (Siemens Medical Solutions). It is expected to open up new perspectives for identifying small brain regions that until now have remained outside the grasp of the spatial resolution of conventional PET cameras.
A comparative analysis between the results of the HRRT lens (at a 2.5-mm resolution) and the HR+ lens (Siemens Medical Solutions, at a resolution of 4.5 mm) has validated the HRRT camera for use in brain imaging of the neuronal (1) dopamine transporter called DAT. The study also revealed that this camera’s high spatial resolution makes it possible to better quantify the specific DAT-binding of the 11C-PE2I molecule labelled for these tests. This better quantification capacity can be implemented in the study of neurodegenerative diseases such as Parkinson’s, where DAT is the first molecule to show decline (even before functional loss), thus making it possible to screen for the disease earlier on.
To achieve this result, brain imaging was run on 26 subjects of the same age: 15 with the HRRT lens, and 11 with the HR+. The binding potential (BP) (2) of 11C-PE2I was assessed at the striatum.
The results highlighted that the BP values and inter-individual variability obtained with data from the striatum were not significantly different between the HRRT and HR+ lenses, and at exactly the same resolution in both. (Indeed, the image quality generated by the HRRT lens was intentionally dropped and deteriorated so that the results from the two lens systems could be made comparable and properly compared.)
However, when each lens was allowed to operate at its design resolution (i.e. HRRT at 2.5 mm and HR+ at 4.5 mm), the HRRT lens gave a much clearer visualisation of significantly higher BP values (~ +30%) in the striatum. The age-related decrease in DAT concentrations is in agreement with the literature data and showed no significant difference between the two lens systems used.
The net result is that the HRRT lens was able to confirm certain
observations and open up promising new perspectives.
(1) neuronal transporter:a molecule enabling the recapture of dopamine towards presynaptic neurons (see illustration opposite
(2) an inherent ability of the tracer to bind to the transporter (DAT)
