Accuracy of quantitative ¹⁷⁷Lu SPECT/CT imaging: A systematic review

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Therapy
• Medical Imaging

Background:

• Accurate quantification of lutetium-177 (177Lu) activity in SPECT/CT is vital for developing 177Lu-based peptide receptor radionuclide therapy (PRRT).
• Establishing absorbed dose-effect relationships requires precise 177Lu activity measurements.
• This review addresses the accuracy of quantitative 177Lu SPECT/CT and identifies sources of variability, notably the partial-volume effect (PVE) in small volumes.

Purpose of the Study:

• To systematically review and summarize the reported accuracy of quantitative 177Lu SPECT/CT imaging.
• To highlight key sources of variability affecting 177Lu quantification, with a focus on PVE.
• To assess the potential of standardized procedures for improving quantitative accuracy in clinical PRRT.

Main Methods:

• A systematic review was conducted following PRISMA guidelines.
• Searched MEDLINE, EMBASE, and Web of Science databases without language restrictions.
• Included original studies reporting accuracy of 177Lu activity quantification in SPECT/CT measurements, extracting percentage error and recovery coefficient (RC).

Main Results:

• Analysis of 46 studies revealed a wide range of percentage errors (-102% to 285%) in 177Lu quantification.
• Partial-volume effect (PVE) significantly limits the recovery of 177Lu activity from small volumes.
• Post-reconstruction correction (PVC) methods showed improvements in phantom imaging accuracy and precision for small volumes.

Conclusions:

• The accuracy of 177Lu activity quantification in SPECT/CT imaging is highly variable across studies and is degraded by PVE in small volumes.
• Standardization of calibration, reconstruction, segmentation, and PVC assumptions is recommended to enhance accuracy and precision.
• Improved quantitative accuracy is essential for advancing 177Lu-based PRRT and dose-effect relationship studies.