Three-dimensional performance of a small-diameter positron emission tomograph

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Biophysics

Background:

• Positron Emission Tomography (PET) is crucial for small animal research.
• Previous characterization focused on 2D mode for a novel small-diameter PET scanner.
• 3D PET imaging offers potential for improved data acquisition and analysis.

Purpose of the Study:

• To physically characterize a small-animal PET scanner in 3D mode.
• To compare the performance of 3D mode against the previously reported 2D mode.
• To evaluate the impact of 3D mode on kinetic analysis in small animals.

Main Methods:

• Measured transaxial and axial resolutions (FWHM and FWTM) in 3D mode across the field of view.
• Quantified sensitivity and noise equivalent count rates in 3D and 2D modes.
• Determined scatter fraction in 3D and 2D modes using a phantom.
• Performed comparative kinetic analysis using [11C] SCH 23390 in rats scanned in both 2D and 3D modes.

Main Results:

• 3D transaxial resolution: 2.4 mm FWHM at center, degrading to 4.5 mm; Axial resolution: 4.6 mm FWHM at center, increasing to 5.0 mm.
• 3D sensitivity (4.31 x 10^4 counts s^-1 MBq^-1) was over four times higher than 2D (0.995 x 10^4 counts s^-1 MBq^-1).
• Noise equivalent count rates were significantly higher in 3D.
• Scatter fraction was comparable between 2D and 3D modes (approx. 30%).
• 3D kinetic analysis showed maintained integrity with reduced standard error of fitted parameters.

Conclusions:

• The small-animal PET scanner demonstrates significantly improved sensitivity in 3D mode compared to 2D.
• Resolution characteristics in 3D mode are comparable to 2D.
• 3D operation enhances the precision of quantitative PET studies in small animals, particularly for kinetic modeling.