Evaluation of modified window-based scatter compensation in quantitative 177Lu-SPECT for a ring-configured CZT
Irma Ceric Andelius1,2, Anna Stenvall3, Elias Nilsson3
1Radiation Physics, Department of Haematology, Oncology, and Radiation Physics, Skåne University Hospital, Lund, Sweden. Irma.ceric_andelius@med.lu.se.
EJNMMI Physics
|June 14, 2026
Summary
Modified scatter compensation (MSC) methods improve total activity preservation in 177Lu-quantification using CZT gamma cameras. These advanced techniques offer modest gains in accuracy for small regions but show potential for preserving overall activity measurements.
Area of Science:
- Nuclear Medicine
- Medical Imaging Physics
- Radiopharmaceutical Dosimetry
Background:
- Evaluation of 177Lu-activity quantification using window-based scatter compensation in a ring-configured CZT gamma camera (StarGuide™).
- Extension of previous studies by applying modified scatter compensation (MSC) methods with the StarGuidePlus upgrade.
- MSC methods account for primary photon contamination in scatter windows due to photon tailing, extending to both 113 keV and 208 keV peaks.
Purpose of the Study:
- To assess the bias and precision of 177Lu-activity quantification with MSC and MSC+P methods.
- To compare the performance of MSC and MSC+P against traditional scatter compensation methods (DEW/TEW).
- To evaluate the impact of these methods on activity concentration and total activity measurements in phantoms.
Main Methods:
- Listmode data from NEMA and anthropomorphic phantoms were processed using updated MSC and MSC+P settings.
- Ordered Subset Expectation Maximization (OS-EM) reconstruction with compensation for attenuation, scatter, resolution, and penetration.
- Quantification of activity concentration in defined volumes-of-interest and total phantom activity across multiple time-frames, evaluating bias and precision.
Main Results:
- At 208 keV, MSC and MSC+P yielded similar activity concentrations and total activity estimates with low coefficients of variation (CV).
- At 113 keV, MSC and MSC+P showed slightly better precision but higher bias compared to TEW for activity concentration in the largest sphere.
- MSC and MSC+P significantly reduced bias in total activity quantification compared to TEW at 113 keV.
Conclusions:
- The improvement in activity-concentration accuracy (bias and precision) is modest in small, high-activity regions.
- MSC and MSC+P methods demonstrate potential value in preserving total activity measurements.
- Further investigation may be warranted for optimizing scatter compensation in 177Lu-based therapies.
