. Head-to-head comparison of amyloid-specific PET radioligands [18F]AZD4694 and [11C]AZD2184. Human Amyloid Imaging 2011 Meeting Abstracts. 2011 Jan 15;

Abstract:

[11C]AZD2184 and [18F]AZD4694 are two compounds that have been evaluated in preclinical and clinical studies and showed suitability for imaging and quantification of s-amyloid in brain. They have appeal for use in research programs and [18F]AZD4694 has also potential to be used in multi-center studies involving PET facilities without cyclotron. The present study is a small-scale, direct comparison of the two radioligands aiming at facilitation of translatability of results between studies employing one or the other of the tracers.

Two cognitively normal elderly control subjects (age 50 and 54 years) and four probable Alzheimer's disease patients (age 57}4 years) were involved in the comparison. The subjects were first examined after injection of [11C]AZD2184 (384}79 MBq), and at least 150 minutes later, after injection of [18F]AZD4694 (206}7 MBq). Individual MR images were obtained for segmentation and region of interest delineation. Qualitative image inspection, descriptive assessments of kinetics, and the results of reference region-based kinetic analyses were used to compare the two radioligands.

Visual inspection of normalized images, showed that the distribution and contrast of binding in grey matter areas was similar between the two radioligands. There was negligible white matter binding for [11C]AZD2184 whereas some was observed for [18F]AZD4694 albeit less than half of that seen in cortical areas in AD patients. While kinetics of both radioligands was rapid, the brain uptake, washout and specific binding of [11C]AZD2184 was even faster than for [18F]AZD4694. Regression analysis of regional specific binding ([11C]AZD2184 vs [18F]AZD4694) showed that there was close agreement (slope>0.95) and high degree of correlation (R2>0.85) between results of the radioligands.

In conclusion, these preliminary findings support that visual readings and quantitative results obtained using either radioligand may be translatable to the other one thereby providing opportunities to compare or pool results obtained from different studies.

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