PENELOPE dose assessment comparison for ¹⁷⁷Lu and ¹⁶¹Tb using paediatric computational phantoms

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Therapy
• Medical Physics

Background:

• Targeted Radiopharmaceutical Therapy (TRT) is a rapidly advancing field in nuclear medicine with potential for pediatric cancer treatment.
• Current therapeutic applications of TRT in pediatric oncology are limited, but significant future roles are anticipated.

Purpose of the Study:

• To compare the dosimetric performance of 177Lu and 161Tb radionuclides in pediatric phantoms.
• To evaluate the contribution of different radiation emissions to the total absorbed dose for these radionuclides.
• To validate dosimetry calculations against existing literature values.

Main Methods:

• Utilized Monte Carlo (MC) simulations with the PENELOPE-2018 program.
• Employed pediatric ICRP reference computational phantoms (10 and 15 years old).
• Calculated Specific Absorbed Fractions (SAF) for model validation and organ S-values for dose assessment.

Main Results:

• Dosimetric performances were consistent with literature data.
• 161Tb generally resulted in greater absorbed doses in target volumes compared to 177Lu.
• Higher yields of Auger electrons, Internal Conversion (IC) electrons, and ultrasoft X-rays from 161Tb likely contribute to increased energy deposition.

Conclusions:

• 161Tb demonstrates superior dosimetric performance over 177Lu in pediatric phantoms for TRT.
• The enhanced energy deposition of 161Tb is attributed to its unique emission characteristics.
• Standardized parametrization guidelines for MC dose coefficient assessment across different tools are crucial for reliable dosimetry.