Improving quantitative dosimetry in (177)Lu-DOTATATE SPECT by energy window-based scatter corrections

Area of Science:

• Nuclear medicine
• Medical imaging
• Radiopharmaceutical therapy

Background:

• Patient-specific dosimetry of lutetium-177 ((177)Lu)-DOTATATE is crucial for neuroendocrine tumor treatment due to variable patient uptake.
• Accurate dosimetry relies on reliable single photon emission computer tomography (SPECT) imaging, which is influenced by collimator type and scatter correction methods.

Purpose of the Study:

• To experimentally compare different energy window subtraction-based scatter correction methods for (177)Lu SPECT imaging.
• To evaluate the impact of various collimator types and energy windows on quantitative accuracy.

Main Methods:

• SPECT phantom studies were conducted using low-energy high resolution (LEHR), low-energy general purpose (LEGP), and medium-energy general purpose (MEGP) collimators.
• Scatter correction was applied using methods including effective scatter source estimation (ESSE), triple-energy window (TEW), dual-energy window (DEW), double-photopeak window (DPW), and downscatter correction (DSC).
• The performance was assessed by measuring the ratio of activity concentration between spheres and background, corrected for partial volume effects.

Main Results:

• Low-energy collimators and the 208 keV window resulted in artifacts and significant ratio variations.
• The 113 keV window also showed large differences in sphere ratios with low-energy collimators.
• MEGP collimators combined with ESSE correction yielded measured ratios close to true values with minimal sphere-to-sphere differences.

Conclusions:

• Medium-energy general purpose (MEGP) collimators are recommended for quantitative (177)Lu SPECT imaging.
• The effective scatter source estimation (ESSE) technique allows for the utilization of both 113 keV and 208 keV energy peaks.
• Using MEGP collimators and ESSE correction, the difference between calculated and true activity ratios is less than 10%.