Real-time quantitative ex vivo direct autoradiography with 10 μm pixel resolution.

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Biophysics

Background:

• Accurate mapping of positron emission rates in biological specimens is crucial for understanding disease processes and validating kinetic models.
• Existing autoradiography methods may lack the necessary resolution or cost-effectiveness for detailed biological sample analysis.

Purpose of the Study:

• To present and evaluate three novel autoradiography methods for high-resolution positron emission rate mapping of bio-specimen slices.
• To compare the performance characteristics of scientific (LBNL) and conventional charge-coupled devices (CCDs) for this application.

Main Methods:

• Development of three autoradiography systems utilizing one LBNL scientific CCD and two conventional CCDs.
• Characterization of CCD performance, including conversion efficiency, dark current, and spatial resolution.
• Theoretical calculations and preliminary experimental validation using fluorine-18 ([18]F)-labeled tissue samples.

Main Results:

• The LBNL CCD achieved high conversion efficiency (100k e-h pairs/0.5 MeV positron) and low dark current (1.75 × 10⁻⁴ e-/pix/sec), enabling theoretical 86 μm spatial resolution for 100 μm thick [18]F-soaked tissue.
• Conventional CCDs demonstrated lower efficiency (2k e-h pairs/0.5 MeV positron) and higher dark current (200 e-/pix/sec) but offered cost advantages and lower readout frequency requirements.
• Improving conventional CCD efficiency with a phosphor layer enhanced conversion by 17 times but degraded spatial resolution to ~100 μm.

Conclusions:

• The developed CCD-based autoradiography systems provide high-resolution positron emission rate mapping capabilities for biological specimens, including cancerous tissues.
• The LBNL CCD offers superior performance but requires cryogenic cooling, increasing system cost, while conventional CCDs present a more cost-effective alternative with trade-offs in resolution and efficiency.
• These systems are suitable for analyzing biopsy-acquired tissues and corroborating tracer kinetic modeling at the cellular level.