Quantitative ¹⁷⁷Lu SPECT/CT imaging for personalized dosimetry using a ring-shaped CZT-based camera.

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Radiopharmaceutical Therapy

Background:

• Accurate dosimetry is essential for radiopharmaceutical therapy (177Lu-RPT) using quantitative SPECT/CT imaging.
• Developing suitable reconstruction protocols is critical for reliable SPECT/CT quantitative performance.
• This study evaluates a CZT-based camera for 177Lu imaging.

Purpose of the Study:

• To characterize the quantitative performance of a ring-shaped CZT-based camera for 177Lu imaging.
• To compare two reconstruction algorithms: OSEM and BSREM (Q.Clear) for 177Lu dosimetry.
• To establish foundations for defining a reconstruction protocol for accurate 177Lu-RPT dosimetry.

Main Methods:

• Acquired 177Lu-filled phantoms using a StarGuide™ camera.
• Reconstructed images using manufacturer implementations of OSEM (GE-OSEM) and BSREM (Q.Clear) with varying iterations and subsets.
• Evaluated quantification accuracy, noise, recovery coefficients (RCs), and spatial resolution in phantoms and patient cohorts.

Main Results:

• Activity accuracy was within 10% for all reconstructions, despite septal penetration.
• Both OSEM and BSREM improved spatial resolution and RCs with increased updates, but BSREM showed better noise reduction.
• Carefully selected parameters yielded comparable noise, spatial resolution (~1 cm), and RCs across algorithms in phantoms and patients.

Conclusions:

• Accurate 177Lu quantification is feasible with StarGuide™ SPECT/CT.
• GE-OSEM provides a valid alternative to Q.Clear, demonstrating comparable performance for phantom and patient dosimetry.
• Further investigation into the impact of septal penetration on dosimetry is warranted.