Multicenter comparison of radionuclide calibrators and SPECT/CT protocols for quantitative ¹⁷⁷Lu   imaging in...

Area of Science:

• Nuclear medicine
• Medical imaging
• Radiopharmaceutical therapy

Background:

• [Formula: see text]-based therapies are increasingly used for neuroendocrine tumors and prostate cancer.
• Accurate quantification of [Formula: see text] is essential for effective treatment delivery and dosimetry.
• Lack of standardization in [Formula: see text] measurement leads to inter-system variability, impacting multi-center clinical trials.

Purpose of the Study:

• To assess the accuracy and variability of [Formula: see text] measurements using radionuclide calibrators (RNCs) and SPECT/CT across different systems and hospitals.
• To identify sources of variability in quantitative [Formula: see text]-SPECT/CT imaging.
• To evaluate the impact of standardized protocols on measurement consistency.

Main Methods:

• Utilized a uniform cylindrical phantom and a NEMA phantom with hot spheres, prepared with traceable [Formula: see text] activities.
• Performed SPECT/CT imaging at 8 hospitals using 13 different systems (9 conventional, 4 3D CZT).
• Evaluated RNC accuracy with vials and assessed SPECT/CT system calibration, image calibration factors (ICFs), and effective resolution (recovery coefficients, RCs) using both site-specific and standardized protocols.

Main Results:

• RNC measurements showed up to 11% inter-center variability; SPECT quantification of the cylindrical phantom varied up to 20%.
• Image quality varied significantly with clinical protocols (36% difference in RCs), although ICFs were consistent within system types.
• Standardized reconstruction reduced RCs variability (max 12% difference) within system types, but differences between system types persisted (33% difference) even with standardized acquisition and reconstruction.

Conclusions:

• Current [Formula: see text] measurement practices exhibit significant variability in quantification and image quality.
• Harmonization efforts are necessary to improve multicenter reproducibility of quantitative [Formula: see text]-SPECT/CT.
• Prioritizing standardized calibration and reconstruction protocols is crucial for reliable multicenter clinical trials.