Validation of procedures for quantitative whole-body autoradiography using digital imaging

Area of Science:

• Pharmacokinetics and Drug Metabolism
• Radiopharmaceutical Sciences
• Biomedical Imaging

Background:

• Quantitative whole-body autoradiography (QWBA) is crucial for assessing drug distribution.
• Direct tissue analysis is the gold standard but is labor-intensive.
• Digital analysis of autoradiograms offers a potentially more efficient method.

Purpose of the Study:

• To validate digital analysis of autoradiograms against direct tissue analysis for radioactivity quantification.
• To describe the preparation and calibration of standards for QWBA.
• To establish the reliability of digital imaging systems in radioactivity measurement.

Main Methods:

• Administered 14C radioactivity intravenously to male Long-Evans hooded rats.
• Performed whole-body autoradiography and collected blood and 16 tissue samples.
• Analyzed autoradiogram optical densities using a RAS3000 digital imaging system.

Main Results:

• Digital autoradiogram analysis showed high correlation (r=0.956) with direct tissue analysis.
• Linear regression revealed a near 1:1 correlation (slope=0.97, r2=0.913).
• Discrepancies in three tissues were attributed to cross-contamination during sample excision.

Conclusions:

• Digital analysis of autoradiograms provides comparable and reliable tissue radioactivity concentrations.
• This digital method serves as a valuable adjunct to conventional tissue analysis.
• The findings support the use of digital autoradiography for accurate pharmacokinetic studies.