Radioactive spheres without inactive wall for lesion simulation in PET

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Radiophysics

Background:

• Positron Emission Tomography (PET) and PET/CT are crucial for medical diagnosis, staging, therapy monitoring, and radiotherapy planning.
• Current PET phantoms often use hollow plastic or glass spheres filled with radioactive solutions.
• Inactive walls of conventional spheres introduce quantification errors, especially with background activity.

Purpose of the Study:

• To develop and evaluate novel radioactive wax spheres for more accurate PET phantom simulations.
• To address the limitations of traditional fillable spheres in reflecting in-vivo conditions.
• To improve quantification accuracy in PET imaging applications.

Main Methods:

• Radioactive wax spheres were fabricated for use in PET phantoms.
• Diffusion of radioactivity into surrounding water was assessed.
• Homogeneity and attenuation properties of wax spheres were evaluated for PET energy photons.
• Recovery coefficients were measured for wax spheres of varying diameters (6-28 mm) and compared to fillable plastic spheres.

Main Results:

• Radioactive wax spheres demonstrated minimal activity diffusion into surrounding water.
• Sufficient homogeneity and water-equivalent attenuation properties were confirmed for PET energies.
• Recovery coefficients for wax spheres were significantly higher, up to 21%, compared to fillable plastic spheres.
• Improved quantification accuracy was observed with wax spheres, particularly in the presence of background activity.

Conclusions:

• Radioactive wax spheres provide a flexible and accurate alternative to traditional PET phantom materials.
• These spheres enhance the reliability of PET phantom studies, leading to better diagnostic and therapeutic applications.
• The improved quantification accuracy of wax spheres is critical for advancing PET imaging research and clinical practice.