A validation protocol for¹⁷⁷Lu-SPECT image quantification as a basis for multi-centre kidney dosimetry

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Radiotherapy Physics

Background:

• Multicenter molecular radiotherapy studies face challenges in dosimetry result comparability.
• Standardized Lutetium-177 single-photon emission computed tomography (¹⁷⁷Lu-SPECT) quantification is crucial for accurate dosimetry.

Purpose of the Study:

• To develop and validate a protocol for equivalent ¹⁷⁷Lu-SPECT quantification across different institutions.
• To establish a test exercise with an action level for multicenter dosimetry validation.

Main Methods:

• ¹⁷⁷Lu-SPECT/CT imaging of kidney phantoms with non-uniform activity distributions was performed at five hospitals.
• Twelve quantification systems (QSs), combining camera, reconstruction, and analysis methods, were evaluated.
• Three dosimetry approaches (site-specific and two centralized) were compared against a reference value, with an action level set at ±10% deviation.

Main Results:

• The site-specific approach showed deviations >10% for six of 12 QS.
• Centralized approaches yielded deviations within 10% for nine of nine and seven of nine QS.
• Sites with non-compliant QS were required to implement action plans for method optimization.

Conclusions:

• A combined quantification test and action level provides initial validation for multicenter dosimetry.
• This protocol facilitates further development towards equivalent ¹⁷⁷Lu-SPECT quantification.
• The approach aids in improving the reliability and comparability of dosimetry in molecular radiotherapy.